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1// SPDX-License-Identifier: GPL-2.0
2/* ePAPR hypervisor byte channel device driver
3 *
4 * Copyright 2009-2011 Freescale Semiconductor, Inc.
5 *
6 * Author: Timur Tabi <timur@freescale.com>
7 *
8 * This driver support three distinct interfaces, all of which are related to
9 * ePAPR hypervisor byte channels.
10 *
11 * 1) An early-console (udbg) driver. This provides early console output
12 * through a byte channel. The byte channel handle must be specified in a
13 * Kconfig option.
14 *
15 * 2) A normal console driver. Output is sent to the byte channel designated
16 * for stdout in the device tree. The console driver is for handling kernel
17 * printk calls.
18 *
19 * 3) A tty driver, which is used to handle user-space input and output. The
20 * byte channel used for the console is designated as the default tty.
21 */
22
23#include <linux/init.h>
24#include <linux/slab.h>
25#include <linux/err.h>
26#include <linux/interrupt.h>
27#include <linux/fs.h>
28#include <linux/poll.h>
29#include <asm/epapr_hcalls.h>
30#include <linux/of.h>
31#include <linux/of_irq.h>
32#include <linux/platform_device.h>
33#include <linux/cdev.h>
34#include <linux/console.h>
35#include <linux/tty.h>
36#include <linux/tty_flip.h>
37#include <linux/circ_buf.h>
38#include <asm/udbg.h>
39
40/* The size of the transmit circular buffer. This must be a power of two. */
41#define BUF_SIZE 2048
42
43/* Per-byte channel private data */
44struct ehv_bc_data {
45 struct device *dev;
46 struct tty_port port;
47 uint32_t handle;
48 unsigned int rx_irq;
49 unsigned int tx_irq;
50
51 spinlock_t lock; /* lock for transmit buffer */
52 unsigned char buf[BUF_SIZE]; /* transmit circular buffer */
53 unsigned int head; /* circular buffer head */
54 unsigned int tail; /* circular buffer tail */
55
56 int tx_irq_enabled; /* true == TX interrupt is enabled */
57};
58
59/* Array of byte channel objects */
60static struct ehv_bc_data *bcs;
61
62/* Byte channel handle for stdout (and stdin), taken from device tree */
63static unsigned int stdout_bc;
64
65/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
66static unsigned int stdout_irq;
67
68/**************************** SUPPORT FUNCTIONS ****************************/
69
70/*
71 * Enable the transmit interrupt
72 *
73 * Unlike a serial device, byte channels have no mechanism for disabling their
74 * own receive or transmit interrupts. To emulate that feature, we toggle
75 * the IRQ in the kernel.
76 *
77 * We cannot just blindly call enable_irq() or disable_irq(), because these
78 * calls are reference counted. This means that we cannot call enable_irq()
79 * if interrupts are already enabled. This can happen in two situations:
80 *
81 * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
82 * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
83 *
84 * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
85 */
86static void enable_tx_interrupt(struct ehv_bc_data *bc)
87{
88 if (!bc->tx_irq_enabled) {
89 enable_irq(bc->tx_irq);
90 bc->tx_irq_enabled = 1;
91 }
92}
93
94static void disable_tx_interrupt(struct ehv_bc_data *bc)
95{
96 if (bc->tx_irq_enabled) {
97 disable_irq_nosync(bc->tx_irq);
98 bc->tx_irq_enabled = 0;
99 }
100}
101
102/*
103 * find the byte channel handle to use for the console
104 *
105 * The byte channel to be used for the console is specified via a "stdout"
106 * property in the /chosen node.
107 */
108static int find_console_handle(void)
109{
110 struct device_node *np = of_stdout;
111 const uint32_t *iprop;
112
113 /* We don't care what the aliased node is actually called. We only
114 * care if it's compatible with "epapr,hv-byte-channel", because that
115 * indicates that it's a byte channel node.
116 */
117 if (!np || !of_device_is_compatible(np, "epapr,hv-byte-channel"))
118 return 0;
119
120 stdout_irq = irq_of_parse_and_map(np, 0);
121 if (stdout_irq == NO_IRQ) {
122 pr_err("ehv-bc: no 'interrupts' property in %pOF node\n", np);
123 return 0;
124 }
125
126 /*
127 * The 'hv-handle' property contains the handle for this byte channel.
128 */
129 iprop = of_get_property(np, "hv-handle", NULL);
130 if (!iprop) {
131 pr_err("ehv-bc: no 'hv-handle' property in %pOFn node\n",
132 np);
133 return 0;
134 }
135 stdout_bc = be32_to_cpu(*iprop);
136 return 1;
137}
138
139static unsigned int local_ev_byte_channel_send(unsigned int handle,
140 unsigned int *count,
141 const char *p)
142{
143 char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
144 unsigned int c = *count;
145
146 if (c < sizeof(buffer)) {
147 memcpy(buffer, p, c);
148 memset(&buffer[c], 0, sizeof(buffer) - c);
149 p = buffer;
150 }
151 return ev_byte_channel_send(handle, count, p);
152}
153
154/*************************** EARLY CONSOLE DRIVER ***************************/
155
156#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
157
158/*
159 * send a byte to a byte channel, wait if necessary
160 *
161 * This function sends a byte to a byte channel, and it waits and
162 * retries if the byte channel is full. It returns if the character
163 * has been sent, or if some error has occurred.
164 *
165 */
166static void byte_channel_spin_send(const char data)
167{
168 int ret, count;
169
170 do {
171 count = 1;
172 ret = local_ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
173 &count, &data);
174 } while (ret == EV_EAGAIN);
175}
176
177/*
178 * The udbg subsystem calls this function to display a single character.
179 * We convert CR to a CR/LF.
180 */
181static void ehv_bc_udbg_putc(char c)
182{
183 if (c == '\n')
184 byte_channel_spin_send('\r');
185
186 byte_channel_spin_send(c);
187}
188
189/*
190 * early console initialization
191 *
192 * PowerPC kernels support an early printk console, also known as udbg.
193 * This function must be called via the ppc_md.init_early function pointer.
194 * At this point, the device tree has been unflattened, so we can obtain the
195 * byte channel handle for stdout.
196 *
197 * We only support displaying of characters (putc). We do not support
198 * keyboard input.
199 */
200void __init udbg_init_ehv_bc(void)
201{
202 unsigned int rx_count, tx_count;
203 unsigned int ret;
204
205 /* Verify the byte channel handle */
206 ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
207 &rx_count, &tx_count);
208 if (ret)
209 return;
210
211 udbg_putc = ehv_bc_udbg_putc;
212 register_early_udbg_console();
213
214 udbg_printf("ehv-bc: early console using byte channel handle %u\n",
215 CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
216}
217
218#endif
219
220/****************************** CONSOLE DRIVER ******************************/
221
222static struct tty_driver *ehv_bc_driver;
223
224/*
225 * Byte channel console sending worker function.
226 *
227 * For consoles, if the output buffer is full, we should just spin until it
228 * clears.
229 */
230static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
231 unsigned int count)
232{
233 unsigned int len;
234 int ret = 0;
235
236 while (count) {
237 len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
238 do {
239 ret = local_ev_byte_channel_send(handle, &len, s);
240 } while (ret == EV_EAGAIN);
241 count -= len;
242 s += len;
243 }
244
245 return ret;
246}
247
248/*
249 * write a string to the console
250 *
251 * This function gets called to write a string from the kernel, typically from
252 * a printk(). This function spins until all data is written.
253 *
254 * We copy the data to a temporary buffer because we need to insert a \r in
255 * front of every \n. It's more efficient to copy the data to the buffer than
256 * it is to make multiple hcalls for each character or each newline.
257 */
258static void ehv_bc_console_write(struct console *co, const char *s,
259 unsigned int count)
260{
261 char s2[EV_BYTE_CHANNEL_MAX_BYTES];
262 unsigned int i, j = 0;
263 char c;
264
265 for (i = 0; i < count; i++) {
266 c = *s++;
267
268 if (c == '\n')
269 s2[j++] = '\r';
270
271 s2[j++] = c;
272 if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
273 if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
274 return;
275 j = 0;
276 }
277 }
278
279 if (j)
280 ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
281}
282
283/*
284 * When /dev/console is opened, the kernel iterates the console list looking
285 * for one with ->device and then calls that method. On success, it expects
286 * the passed-in int* to contain the minor number to use.
287 */
288static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
289{
290 *index = co->index;
291
292 return ehv_bc_driver;
293}
294
295static struct console ehv_bc_console = {
296 .name = "ttyEHV",
297 .write = ehv_bc_console_write,
298 .device = ehv_bc_console_device,
299 .flags = CON_PRINTBUFFER | CON_ENABLED,
300};
301
302/*
303 * Console initialization
304 *
305 * This is the first function that is called after the device tree is
306 * available, so here is where we determine the byte channel handle and IRQ for
307 * stdout/stdin, even though that information is used by the tty and character
308 * drivers.
309 */
310static int __init ehv_bc_console_init(void)
311{
312 if (!find_console_handle()) {
313 pr_debug("ehv-bc: stdout is not a byte channel\n");
314 return -ENODEV;
315 }
316
317#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
318 /* Print a friendly warning if the user chose the wrong byte channel
319 * handle for udbg.
320 */
321 if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
322 pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n",
323 CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
324#endif
325
326 /* add_preferred_console() must be called before register_console(),
327 otherwise it won't work. However, we don't want to enumerate all the
328 byte channels here, either, since we only care about one. */
329
330 add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
331 register_console(&ehv_bc_console);
332
333 pr_info("ehv-bc: registered console driver for byte channel %u\n",
334 stdout_bc);
335
336 return 0;
337}
338console_initcall(ehv_bc_console_init);
339
340/******************************** TTY DRIVER ********************************/
341
342/*
343 * byte channel receive interrupt handler
344 *
345 * This ISR is called whenever data is available on a byte channel.
346 */
347static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
348{
349 struct ehv_bc_data *bc = data;
350 unsigned int rx_count, tx_count, len;
351 int count;
352 char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
353 int ret;
354
355 /* Find out how much data needs to be read, and then ask the TTY layer
356 * if it can handle that much. We want to ensure that every byte we
357 * read from the byte channel will be accepted by the TTY layer.
358 */
359 ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
360 count = tty_buffer_request_room(&bc->port, rx_count);
361
362 /* 'count' is the maximum amount of data the TTY layer can accept at
363 * this time. However, during testing, I was never able to get 'count'
364 * to be less than 'rx_count'. I'm not sure whether I'm calling it
365 * correctly.
366 */
367
368 while (count > 0) {
369 len = min_t(unsigned int, count, sizeof(buffer));
370
371 /* Read some data from the byte channel. This function will
372 * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
373 */
374 ev_byte_channel_receive(bc->handle, &len, buffer);
375
376 /* 'len' is now the amount of data that's been received. 'len'
377 * can't be zero, and most likely it's equal to one.
378 */
379
380 /* Pass the received data to the tty layer. */
381 ret = tty_insert_flip_string(&bc->port, buffer, len);
382
383 /* 'ret' is the number of bytes that the TTY layer accepted.
384 * If it's not equal to 'len', then it means the buffer is
385 * full, which should never happen. If it does happen, we can
386 * exit gracefully, but we drop the last 'len - ret' characters
387 * that we read from the byte channel.
388 */
389 if (ret != len)
390 break;
391
392 count -= len;
393 }
394
395 /* Tell the tty layer that we're done. */
396 tty_flip_buffer_push(&bc->port);
397
398 return IRQ_HANDLED;
399}
400
401/*
402 * dequeue the transmit buffer to the hypervisor
403 *
404 * This function, which can be called in interrupt context, dequeues as much
405 * data as possible from the transmit buffer to the byte channel.
406 */
407static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
408{
409 unsigned int count;
410 unsigned int len, ret;
411 unsigned long flags;
412
413 do {
414 spin_lock_irqsave(&bc->lock, flags);
415 len = min_t(unsigned int,
416 CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
417 EV_BYTE_CHANNEL_MAX_BYTES);
418
419 ret = local_ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
420
421 /* 'len' is valid only if the return code is 0 or EV_EAGAIN */
422 if (!ret || (ret == EV_EAGAIN))
423 bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
424
425 count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
426 spin_unlock_irqrestore(&bc->lock, flags);
427 } while (count && !ret);
428
429 spin_lock_irqsave(&bc->lock, flags);
430 if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
431 /*
432 * If we haven't emptied the buffer, then enable the TX IRQ.
433 * We'll get an interrupt when there's more room in the
434 * hypervisor's output buffer.
435 */
436 enable_tx_interrupt(bc);
437 else
438 disable_tx_interrupt(bc);
439 spin_unlock_irqrestore(&bc->lock, flags);
440}
441
442/*
443 * byte channel transmit interrupt handler
444 *
445 * This ISR is called whenever space becomes available for transmitting
446 * characters on a byte channel.
447 */
448static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
449{
450 struct ehv_bc_data *bc = data;
451
452 ehv_bc_tx_dequeue(bc);
453 tty_port_tty_wakeup(&bc->port);
454
455 return IRQ_HANDLED;
456}
457
458/*
459 * This function is called when the tty layer has data for us send. We store
460 * the data first in a circular buffer, and then dequeue as much of that data
461 * as possible.
462 *
463 * We don't need to worry about whether there is enough room in the buffer for
464 * all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty
465 * layer how much data it can safely send to us. We guarantee that
466 * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
467 * too much data.
468 */
469static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s,
470 int count)
471{
472 struct ehv_bc_data *bc = ttys->driver_data;
473 unsigned long flags;
474 unsigned int len;
475 unsigned int written = 0;
476
477 while (1) {
478 spin_lock_irqsave(&bc->lock, flags);
479 len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
480 if (count < len)
481 len = count;
482 if (len) {
483 memcpy(bc->buf + bc->head, s, len);
484 bc->head = (bc->head + len) & (BUF_SIZE - 1);
485 }
486 spin_unlock_irqrestore(&bc->lock, flags);
487 if (!len)
488 break;
489
490 s += len;
491 count -= len;
492 written += len;
493 }
494
495 ehv_bc_tx_dequeue(bc);
496
497 return written;
498}
499
500/*
501 * This function can be called multiple times for a given tty_struct, which is
502 * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
503 *
504 * The tty layer will still call this function even if the device was not
505 * registered (i.e. tty_register_device() was not called). This happens
506 * because tty_register_device() is optional and some legacy drivers don't
507 * use it. So we need to check for that.
508 */
509static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
510{
511 struct ehv_bc_data *bc = &bcs[ttys->index];
512
513 if (!bc->dev)
514 return -ENODEV;
515
516 return tty_port_open(&bc->port, ttys, filp);
517}
518
519/*
520 * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
521 * still call this function to close the tty device. So we can't assume that
522 * the tty port has been initialized.
523 */
524static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
525{
526 struct ehv_bc_data *bc = &bcs[ttys->index];
527
528 if (bc->dev)
529 tty_port_close(&bc->port, ttys, filp);
530}
531
532/*
533 * Return the amount of space in the output buffer
534 *
535 * This is actually a contract between the driver and the tty layer outlining
536 * how much write room the driver can guarantee will be sent OR BUFFERED. This
537 * driver MUST honor the return value.
538 */
539static int ehv_bc_tty_write_room(struct tty_struct *ttys)
540{
541 struct ehv_bc_data *bc = ttys->driver_data;
542 unsigned long flags;
543 int count;
544
545 spin_lock_irqsave(&bc->lock, flags);
546 count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
547 spin_unlock_irqrestore(&bc->lock, flags);
548
549 return count;
550}
551
552/*
553 * Stop sending data to the tty layer
554 *
555 * This function is called when the tty layer's input buffers are getting full,
556 * so the driver should stop sending it data. The easiest way to do this is to
557 * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
558 * called.
559 *
560 * The hypervisor will continue to queue up any incoming data. If there is any
561 * data in the queue when the RX interrupt is enabled, we'll immediately get an
562 * RX interrupt.
563 */
564static void ehv_bc_tty_throttle(struct tty_struct *ttys)
565{
566 struct ehv_bc_data *bc = ttys->driver_data;
567
568 disable_irq(bc->rx_irq);
569}
570
571/*
572 * Resume sending data to the tty layer
573 *
574 * This function is called after previously calling ehv_bc_tty_throttle(). The
575 * tty layer's input buffers now have more room, so the driver can resume
576 * sending it data.
577 */
578static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
579{
580 struct ehv_bc_data *bc = ttys->driver_data;
581
582 /* If there is any data in the queue when the RX interrupt is enabled,
583 * we'll immediately get an RX interrupt.
584 */
585 enable_irq(bc->rx_irq);
586}
587
588static void ehv_bc_tty_hangup(struct tty_struct *ttys)
589{
590 struct ehv_bc_data *bc = ttys->driver_data;
591
592 ehv_bc_tx_dequeue(bc);
593 tty_port_hangup(&bc->port);
594}
595
596/*
597 * TTY driver operations
598 *
599 * If we could ask the hypervisor how much data is still in the TX buffer, or
600 * at least how big the TX buffers are, then we could implement the
601 * .wait_until_sent and .chars_in_buffer functions.
602 */
603static const struct tty_operations ehv_bc_ops = {
604 .open = ehv_bc_tty_open,
605 .close = ehv_bc_tty_close,
606 .write = ehv_bc_tty_write,
607 .write_room = ehv_bc_tty_write_room,
608 .throttle = ehv_bc_tty_throttle,
609 .unthrottle = ehv_bc_tty_unthrottle,
610 .hangup = ehv_bc_tty_hangup,
611};
612
613/*
614 * initialize the TTY port
615 *
616 * This function will only be called once, no matter how many times
617 * ehv_bc_tty_open() is called. That's why we register the ISR here, and also
618 * why we initialize tty_struct-related variables here.
619 */
620static int ehv_bc_tty_port_activate(struct tty_port *port,
621 struct tty_struct *ttys)
622{
623 struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
624 int ret;
625
626 ttys->driver_data = bc;
627
628 ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
629 if (ret < 0) {
630 dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
631 bc->rx_irq, ret);
632 return ret;
633 }
634
635 /* request_irq also enables the IRQ */
636 bc->tx_irq_enabled = 1;
637
638 ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
639 if (ret < 0) {
640 dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
641 bc->tx_irq, ret);
642 free_irq(bc->rx_irq, bc);
643 return ret;
644 }
645
646 /* The TX IRQ is enabled only when we can't write all the data to the
647 * byte channel at once, so by default it's disabled.
648 */
649 disable_tx_interrupt(bc);
650
651 return 0;
652}
653
654static void ehv_bc_tty_port_shutdown(struct tty_port *port)
655{
656 struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
657
658 free_irq(bc->tx_irq, bc);
659 free_irq(bc->rx_irq, bc);
660}
661
662static const struct tty_port_operations ehv_bc_tty_port_ops = {
663 .activate = ehv_bc_tty_port_activate,
664 .shutdown = ehv_bc_tty_port_shutdown,
665};
666
667static int ehv_bc_tty_probe(struct platform_device *pdev)
668{
669 struct device_node *np = pdev->dev.of_node;
670 struct ehv_bc_data *bc;
671 const uint32_t *iprop;
672 unsigned int handle;
673 int ret;
674 static unsigned int index = 1;
675 unsigned int i;
676
677 iprop = of_get_property(np, "hv-handle", NULL);
678 if (!iprop) {
679 dev_err(&pdev->dev, "no 'hv-handle' property in %pOFn node\n",
680 np);
681 return -ENODEV;
682 }
683
684 /* We already told the console layer that the index for the console
685 * device is zero, so we need to make sure that we use that index when
686 * we probe the console byte channel node.
687 */
688 handle = be32_to_cpu(*iprop);
689 i = (handle == stdout_bc) ? 0 : index++;
690 bc = &bcs[i];
691
692 bc->handle = handle;
693 bc->head = 0;
694 bc->tail = 0;
695 spin_lock_init(&bc->lock);
696
697 bc->rx_irq = irq_of_parse_and_map(np, 0);
698 bc->tx_irq = irq_of_parse_and_map(np, 1);
699 if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) {
700 dev_err(&pdev->dev, "no 'interrupts' property in %pOFn node\n",
701 np);
702 ret = -ENODEV;
703 goto error;
704 }
705
706 tty_port_init(&bc->port);
707 bc->port.ops = &ehv_bc_tty_port_ops;
708
709 bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i,
710 &pdev->dev);
711 if (IS_ERR(bc->dev)) {
712 ret = PTR_ERR(bc->dev);
713 dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
714 goto error;
715 }
716
717 dev_set_drvdata(&pdev->dev, bc);
718
719 dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
720 ehv_bc_driver->name, i, bc->handle);
721
722 return 0;
723
724error:
725 tty_port_destroy(&bc->port);
726 irq_dispose_mapping(bc->tx_irq);
727 irq_dispose_mapping(bc->rx_irq);
728
729 memset(bc, 0, sizeof(struct ehv_bc_data));
730 return ret;
731}
732
733static const struct of_device_id ehv_bc_tty_of_ids[] = {
734 { .compatible = "epapr,hv-byte-channel" },
735 {}
736};
737
738static struct platform_driver ehv_bc_tty_driver = {
739 .driver = {
740 .name = "ehv-bc",
741 .of_match_table = ehv_bc_tty_of_ids,
742 .suppress_bind_attrs = true,
743 },
744 .probe = ehv_bc_tty_probe,
745};
746
747/**
748 * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
749 *
750 * This function is called when this driver is loaded.
751 */
752static int __init ehv_bc_init(void)
753{
754 struct device_node *np;
755 unsigned int count = 0; /* Number of elements in bcs[] */
756 int ret;
757
758 pr_info("ePAPR hypervisor byte channel driver\n");
759
760 /* Count the number of byte channels */
761 for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
762 count++;
763
764 if (!count)
765 return -ENODEV;
766
767 /* The array index of an element in bcs[] is the same as the tty index
768 * for that element. If you know the address of an element in the
769 * array, then you can use pointer math (e.g. "bc - bcs") to get its
770 * tty index.
771 */
772 bcs = kcalloc(count, sizeof(struct ehv_bc_data), GFP_KERNEL);
773 if (!bcs)
774 return -ENOMEM;
775
776 ehv_bc_driver = alloc_tty_driver(count);
777 if (!ehv_bc_driver) {
778 ret = -ENOMEM;
779 goto err_free_bcs;
780 }
781
782 ehv_bc_driver->driver_name = "ehv-bc";
783 ehv_bc_driver->name = ehv_bc_console.name;
784 ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
785 ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
786 ehv_bc_driver->init_termios = tty_std_termios;
787 ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
788 tty_set_operations(ehv_bc_driver, &ehv_bc_ops);
789
790 ret = tty_register_driver(ehv_bc_driver);
791 if (ret) {
792 pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
793 goto err_put_tty_driver;
794 }
795
796 ret = platform_driver_register(&ehv_bc_tty_driver);
797 if (ret) {
798 pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
799 ret);
800 goto err_deregister_tty_driver;
801 }
802
803 return 0;
804
805err_deregister_tty_driver:
806 tty_unregister_driver(ehv_bc_driver);
807err_put_tty_driver:
808 put_tty_driver(ehv_bc_driver);
809err_free_bcs:
810 kfree(bcs);
811
812 return ret;
813}
814device_initcall(ehv_bc_init);
1/* ePAPR hypervisor byte channel device driver
2 *
3 * Copyright 2009-2011 Freescale Semiconductor, Inc.
4 *
5 * Author: Timur Tabi <timur@freescale.com>
6 *
7 * This file is licensed under the terms of the GNU General Public License
8 * version 2. This program is licensed "as is" without any warranty of any
9 * kind, whether express or implied.
10 *
11 * This driver support three distinct interfaces, all of which are related to
12 * ePAPR hypervisor byte channels.
13 *
14 * 1) An early-console (udbg) driver. This provides early console output
15 * through a byte channel. The byte channel handle must be specified in a
16 * Kconfig option.
17 *
18 * 2) A normal console driver. Output is sent to the byte channel designated
19 * for stdout in the device tree. The console driver is for handling kernel
20 * printk calls.
21 *
22 * 3) A tty driver, which is used to handle user-space input and output. The
23 * byte channel used for the console is designated as the default tty.
24 */
25
26#include <linux/module.h>
27#include <linux/init.h>
28#include <linux/slab.h>
29#include <linux/err.h>
30#include <linux/interrupt.h>
31#include <linux/fs.h>
32#include <linux/poll.h>
33#include <asm/epapr_hcalls.h>
34#include <linux/of.h>
35#include <linux/platform_device.h>
36#include <linux/cdev.h>
37#include <linux/console.h>
38#include <linux/tty.h>
39#include <linux/tty_flip.h>
40#include <linux/circ_buf.h>
41#include <asm/udbg.h>
42
43/* The size of the transmit circular buffer. This must be a power of two. */
44#define BUF_SIZE 2048
45
46/* Per-byte channel private data */
47struct ehv_bc_data {
48 struct device *dev;
49 struct tty_port port;
50 uint32_t handle;
51 unsigned int rx_irq;
52 unsigned int tx_irq;
53
54 spinlock_t lock; /* lock for transmit buffer */
55 unsigned char buf[BUF_SIZE]; /* transmit circular buffer */
56 unsigned int head; /* circular buffer head */
57 unsigned int tail; /* circular buffer tail */
58
59 int tx_irq_enabled; /* true == TX interrupt is enabled */
60};
61
62/* Array of byte channel objects */
63static struct ehv_bc_data *bcs;
64
65/* Byte channel handle for stdout (and stdin), taken from device tree */
66static unsigned int stdout_bc;
67
68/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
69static unsigned int stdout_irq;
70
71/**************************** SUPPORT FUNCTIONS ****************************/
72
73/*
74 * Enable the transmit interrupt
75 *
76 * Unlike a serial device, byte channels have no mechanism for disabling their
77 * own receive or transmit interrupts. To emulate that feature, we toggle
78 * the IRQ in the kernel.
79 *
80 * We cannot just blindly call enable_irq() or disable_irq(), because these
81 * calls are reference counted. This means that we cannot call enable_irq()
82 * if interrupts are already enabled. This can happen in two situations:
83 *
84 * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
85 * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
86 *
87 * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
88 */
89static void enable_tx_interrupt(struct ehv_bc_data *bc)
90{
91 if (!bc->tx_irq_enabled) {
92 enable_irq(bc->tx_irq);
93 bc->tx_irq_enabled = 1;
94 }
95}
96
97static void disable_tx_interrupt(struct ehv_bc_data *bc)
98{
99 if (bc->tx_irq_enabled) {
100 disable_irq_nosync(bc->tx_irq);
101 bc->tx_irq_enabled = 0;
102 }
103}
104
105/*
106 * find the byte channel handle to use for the console
107 *
108 * The byte channel to be used for the console is specified via a "stdout"
109 * property in the /chosen node.
110 *
111 * For compatible with legacy device trees, we also look for a "stdout" alias.
112 */
113static int find_console_handle(void)
114{
115 struct device_node *np, *np2;
116 const char *sprop = NULL;
117 const uint32_t *iprop;
118
119 np = of_find_node_by_path("/chosen");
120 if (np)
121 sprop = of_get_property(np, "stdout-path", NULL);
122
123 if (!np || !sprop) {
124 of_node_put(np);
125 np = of_find_node_by_name(NULL, "aliases");
126 if (np)
127 sprop = of_get_property(np, "stdout", NULL);
128 }
129
130 if (!sprop) {
131 of_node_put(np);
132 return 0;
133 }
134
135 /* We don't care what the aliased node is actually called. We only
136 * care if it's compatible with "epapr,hv-byte-channel", because that
137 * indicates that it's a byte channel node. We use a temporary
138 * variable, 'np2', because we can't release 'np' until we're done with
139 * 'sprop'.
140 */
141 np2 = of_find_node_by_path(sprop);
142 of_node_put(np);
143 np = np2;
144 if (!np) {
145 pr_warning("ehv-bc: stdout node '%s' does not exist\n", sprop);
146 return 0;
147 }
148
149 /* Is it a byte channel? */
150 if (!of_device_is_compatible(np, "epapr,hv-byte-channel")) {
151 of_node_put(np);
152 return 0;
153 }
154
155 stdout_irq = irq_of_parse_and_map(np, 0);
156 if (stdout_irq == NO_IRQ) {
157 pr_err("ehv-bc: no 'interrupts' property in %s node\n", sprop);
158 of_node_put(np);
159 return 0;
160 }
161
162 /*
163 * The 'hv-handle' property contains the handle for this byte channel.
164 */
165 iprop = of_get_property(np, "hv-handle", NULL);
166 if (!iprop) {
167 pr_err("ehv-bc: no 'hv-handle' property in %s node\n",
168 np->name);
169 of_node_put(np);
170 return 0;
171 }
172 stdout_bc = be32_to_cpu(*iprop);
173
174 of_node_put(np);
175 return 1;
176}
177
178/*************************** EARLY CONSOLE DRIVER ***************************/
179
180#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
181
182/*
183 * send a byte to a byte channel, wait if necessary
184 *
185 * This function sends a byte to a byte channel, and it waits and
186 * retries if the byte channel is full. It returns if the character
187 * has been sent, or if some error has occurred.
188 *
189 */
190static void byte_channel_spin_send(const char data)
191{
192 int ret, count;
193
194 do {
195 count = 1;
196 ret = ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
197 &count, &data);
198 } while (ret == EV_EAGAIN);
199}
200
201/*
202 * The udbg subsystem calls this function to display a single character.
203 * We convert CR to a CR/LF.
204 */
205static void ehv_bc_udbg_putc(char c)
206{
207 if (c == '\n')
208 byte_channel_spin_send('\r');
209
210 byte_channel_spin_send(c);
211}
212
213/*
214 * early console initialization
215 *
216 * PowerPC kernels support an early printk console, also known as udbg.
217 * This function must be called via the ppc_md.init_early function pointer.
218 * At this point, the device tree has been unflattened, so we can obtain the
219 * byte channel handle for stdout.
220 *
221 * We only support displaying of characters (putc). We do not support
222 * keyboard input.
223 */
224void __init udbg_init_ehv_bc(void)
225{
226 unsigned int rx_count, tx_count;
227 unsigned int ret;
228
229 /* Verify the byte channel handle */
230 ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
231 &rx_count, &tx_count);
232 if (ret)
233 return;
234
235 udbg_putc = ehv_bc_udbg_putc;
236 register_early_udbg_console();
237
238 udbg_printf("ehv-bc: early console using byte channel handle %u\n",
239 CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
240}
241
242#endif
243
244/****************************** CONSOLE DRIVER ******************************/
245
246static struct tty_driver *ehv_bc_driver;
247
248/*
249 * Byte channel console sending worker function.
250 *
251 * For consoles, if the output buffer is full, we should just spin until it
252 * clears.
253 */
254static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
255 unsigned int count)
256{
257 unsigned int len;
258 int ret = 0;
259
260 while (count) {
261 len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
262 do {
263 ret = ev_byte_channel_send(handle, &len, s);
264 } while (ret == EV_EAGAIN);
265 count -= len;
266 s += len;
267 }
268
269 return ret;
270}
271
272/*
273 * write a string to the console
274 *
275 * This function gets called to write a string from the kernel, typically from
276 * a printk(). This function spins until all data is written.
277 *
278 * We copy the data to a temporary buffer because we need to insert a \r in
279 * front of every \n. It's more efficient to copy the data to the buffer than
280 * it is to make multiple hcalls for each character or each newline.
281 */
282static void ehv_bc_console_write(struct console *co, const char *s,
283 unsigned int count)
284{
285 char s2[EV_BYTE_CHANNEL_MAX_BYTES];
286 unsigned int i, j = 0;
287 char c;
288
289 for (i = 0; i < count; i++) {
290 c = *s++;
291
292 if (c == '\n')
293 s2[j++] = '\r';
294
295 s2[j++] = c;
296 if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
297 if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
298 return;
299 j = 0;
300 }
301 }
302
303 if (j)
304 ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
305}
306
307/*
308 * When /dev/console is opened, the kernel iterates the console list looking
309 * for one with ->device and then calls that method. On success, it expects
310 * the passed-in int* to contain the minor number to use.
311 */
312static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
313{
314 *index = co->index;
315
316 return ehv_bc_driver;
317}
318
319static struct console ehv_bc_console = {
320 .name = "ttyEHV",
321 .write = ehv_bc_console_write,
322 .device = ehv_bc_console_device,
323 .flags = CON_PRINTBUFFER | CON_ENABLED,
324};
325
326/*
327 * Console initialization
328 *
329 * This is the first function that is called after the device tree is
330 * available, so here is where we determine the byte channel handle and IRQ for
331 * stdout/stdin, even though that information is used by the tty and character
332 * drivers.
333 */
334static int __init ehv_bc_console_init(void)
335{
336 if (!find_console_handle()) {
337 pr_debug("ehv-bc: stdout is not a byte channel\n");
338 return -ENODEV;
339 }
340
341#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
342 /* Print a friendly warning if the user chose the wrong byte channel
343 * handle for udbg.
344 */
345 if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
346 pr_warning("ehv-bc: udbg handle %u is not the stdout handle\n",
347 CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
348#endif
349
350 /* add_preferred_console() must be called before register_console(),
351 otherwise it won't work. However, we don't want to enumerate all the
352 byte channels here, either, since we only care about one. */
353
354 add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
355 register_console(&ehv_bc_console);
356
357 pr_info("ehv-bc: registered console driver for byte channel %u\n",
358 stdout_bc);
359
360 return 0;
361}
362console_initcall(ehv_bc_console_init);
363
364/******************************** TTY DRIVER ********************************/
365
366/*
367 * byte channel receive interupt handler
368 *
369 * This ISR is called whenever data is available on a byte channel.
370 */
371static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
372{
373 struct ehv_bc_data *bc = data;
374 struct tty_struct *ttys = tty_port_tty_get(&bc->port);
375 unsigned int rx_count, tx_count, len;
376 int count;
377 char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
378 int ret;
379
380 /* ttys could be NULL during a hangup */
381 if (!ttys)
382 return IRQ_HANDLED;
383
384 /* Find out how much data needs to be read, and then ask the TTY layer
385 * if it can handle that much. We want to ensure that every byte we
386 * read from the byte channel will be accepted by the TTY layer.
387 */
388 ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
389 count = tty_buffer_request_room(ttys, rx_count);
390
391 /* 'count' is the maximum amount of data the TTY layer can accept at
392 * this time. However, during testing, I was never able to get 'count'
393 * to be less than 'rx_count'. I'm not sure whether I'm calling it
394 * correctly.
395 */
396
397 while (count > 0) {
398 len = min_t(unsigned int, count, sizeof(buffer));
399
400 /* Read some data from the byte channel. This function will
401 * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
402 */
403 ev_byte_channel_receive(bc->handle, &len, buffer);
404
405 /* 'len' is now the amount of data that's been received. 'len'
406 * can't be zero, and most likely it's equal to one.
407 */
408
409 /* Pass the received data to the tty layer. */
410 ret = tty_insert_flip_string(ttys, buffer, len);
411
412 /* 'ret' is the number of bytes that the TTY layer accepted.
413 * If it's not equal to 'len', then it means the buffer is
414 * full, which should never happen. If it does happen, we can
415 * exit gracefully, but we drop the last 'len - ret' characters
416 * that we read from the byte channel.
417 */
418 if (ret != len)
419 break;
420
421 count -= len;
422 }
423
424 /* Tell the tty layer that we're done. */
425 tty_flip_buffer_push(ttys);
426
427 tty_kref_put(ttys);
428
429 return IRQ_HANDLED;
430}
431
432/*
433 * dequeue the transmit buffer to the hypervisor
434 *
435 * This function, which can be called in interrupt context, dequeues as much
436 * data as possible from the transmit buffer to the byte channel.
437 */
438static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
439{
440 unsigned int count;
441 unsigned int len, ret;
442 unsigned long flags;
443
444 do {
445 spin_lock_irqsave(&bc->lock, flags);
446 len = min_t(unsigned int,
447 CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
448 EV_BYTE_CHANNEL_MAX_BYTES);
449
450 ret = ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
451
452 /* 'len' is valid only if the return code is 0 or EV_EAGAIN */
453 if (!ret || (ret == EV_EAGAIN))
454 bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
455
456 count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
457 spin_unlock_irqrestore(&bc->lock, flags);
458 } while (count && !ret);
459
460 spin_lock_irqsave(&bc->lock, flags);
461 if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
462 /*
463 * If we haven't emptied the buffer, then enable the TX IRQ.
464 * We'll get an interrupt when there's more room in the
465 * hypervisor's output buffer.
466 */
467 enable_tx_interrupt(bc);
468 else
469 disable_tx_interrupt(bc);
470 spin_unlock_irqrestore(&bc->lock, flags);
471}
472
473/*
474 * byte channel transmit interupt handler
475 *
476 * This ISR is called whenever space becomes available for transmitting
477 * characters on a byte channel.
478 */
479static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
480{
481 struct ehv_bc_data *bc = data;
482 struct tty_struct *ttys = tty_port_tty_get(&bc->port);
483
484 ehv_bc_tx_dequeue(bc);
485 if (ttys) {
486 tty_wakeup(ttys);
487 tty_kref_put(ttys);
488 }
489
490 return IRQ_HANDLED;
491}
492
493/*
494 * This function is called when the tty layer has data for us send. We store
495 * the data first in a circular buffer, and then dequeue as much of that data
496 * as possible.
497 *
498 * We don't need to worry about whether there is enough room in the buffer for
499 * all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty
500 * layer how much data it can safely send to us. We guarantee that
501 * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
502 * too much data.
503 */
504static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s,
505 int count)
506{
507 struct ehv_bc_data *bc = ttys->driver_data;
508 unsigned long flags;
509 unsigned int len;
510 unsigned int written = 0;
511
512 while (1) {
513 spin_lock_irqsave(&bc->lock, flags);
514 len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
515 if (count < len)
516 len = count;
517 if (len) {
518 memcpy(bc->buf + bc->head, s, len);
519 bc->head = (bc->head + len) & (BUF_SIZE - 1);
520 }
521 spin_unlock_irqrestore(&bc->lock, flags);
522 if (!len)
523 break;
524
525 s += len;
526 count -= len;
527 written += len;
528 }
529
530 ehv_bc_tx_dequeue(bc);
531
532 return written;
533}
534
535/*
536 * This function can be called multiple times for a given tty_struct, which is
537 * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
538 *
539 * The tty layer will still call this function even if the device was not
540 * registered (i.e. tty_register_device() was not called). This happens
541 * because tty_register_device() is optional and some legacy drivers don't
542 * use it. So we need to check for that.
543 */
544static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
545{
546 struct ehv_bc_data *bc = &bcs[ttys->index];
547
548 if (!bc->dev)
549 return -ENODEV;
550
551 return tty_port_open(&bc->port, ttys, filp);
552}
553
554/*
555 * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
556 * still call this function to close the tty device. So we can't assume that
557 * the tty port has been initialized.
558 */
559static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
560{
561 struct ehv_bc_data *bc = &bcs[ttys->index];
562
563 if (bc->dev)
564 tty_port_close(&bc->port, ttys, filp);
565}
566
567/*
568 * Return the amount of space in the output buffer
569 *
570 * This is actually a contract between the driver and the tty layer outlining
571 * how much write room the driver can guarantee will be sent OR BUFFERED. This
572 * driver MUST honor the return value.
573 */
574static int ehv_bc_tty_write_room(struct tty_struct *ttys)
575{
576 struct ehv_bc_data *bc = ttys->driver_data;
577 unsigned long flags;
578 int count;
579
580 spin_lock_irqsave(&bc->lock, flags);
581 count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
582 spin_unlock_irqrestore(&bc->lock, flags);
583
584 return count;
585}
586
587/*
588 * Stop sending data to the tty layer
589 *
590 * This function is called when the tty layer's input buffers are getting full,
591 * so the driver should stop sending it data. The easiest way to do this is to
592 * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
593 * called.
594 *
595 * The hypervisor will continue to queue up any incoming data. If there is any
596 * data in the queue when the RX interrupt is enabled, we'll immediately get an
597 * RX interrupt.
598 */
599static void ehv_bc_tty_throttle(struct tty_struct *ttys)
600{
601 struct ehv_bc_data *bc = ttys->driver_data;
602
603 disable_irq(bc->rx_irq);
604}
605
606/*
607 * Resume sending data to the tty layer
608 *
609 * This function is called after previously calling ehv_bc_tty_throttle(). The
610 * tty layer's input buffers now have more room, so the driver can resume
611 * sending it data.
612 */
613static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
614{
615 struct ehv_bc_data *bc = ttys->driver_data;
616
617 /* If there is any data in the queue when the RX interrupt is enabled,
618 * we'll immediately get an RX interrupt.
619 */
620 enable_irq(bc->rx_irq);
621}
622
623static void ehv_bc_tty_hangup(struct tty_struct *ttys)
624{
625 struct ehv_bc_data *bc = ttys->driver_data;
626
627 ehv_bc_tx_dequeue(bc);
628 tty_port_hangup(&bc->port);
629}
630
631/*
632 * TTY driver operations
633 *
634 * If we could ask the hypervisor how much data is still in the TX buffer, or
635 * at least how big the TX buffers are, then we could implement the
636 * .wait_until_sent and .chars_in_buffer functions.
637 */
638static const struct tty_operations ehv_bc_ops = {
639 .open = ehv_bc_tty_open,
640 .close = ehv_bc_tty_close,
641 .write = ehv_bc_tty_write,
642 .write_room = ehv_bc_tty_write_room,
643 .throttle = ehv_bc_tty_throttle,
644 .unthrottle = ehv_bc_tty_unthrottle,
645 .hangup = ehv_bc_tty_hangup,
646};
647
648/*
649 * initialize the TTY port
650 *
651 * This function will only be called once, no matter how many times
652 * ehv_bc_tty_open() is called. That's why we register the ISR here, and also
653 * why we initialize tty_struct-related variables here.
654 */
655static int ehv_bc_tty_port_activate(struct tty_port *port,
656 struct tty_struct *ttys)
657{
658 struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
659 int ret;
660
661 ttys->driver_data = bc;
662
663 ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
664 if (ret < 0) {
665 dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
666 bc->rx_irq, ret);
667 return ret;
668 }
669
670 /* request_irq also enables the IRQ */
671 bc->tx_irq_enabled = 1;
672
673 ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
674 if (ret < 0) {
675 dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
676 bc->tx_irq, ret);
677 free_irq(bc->rx_irq, bc);
678 return ret;
679 }
680
681 /* The TX IRQ is enabled only when we can't write all the data to the
682 * byte channel at once, so by default it's disabled.
683 */
684 disable_tx_interrupt(bc);
685
686 return 0;
687}
688
689static void ehv_bc_tty_port_shutdown(struct tty_port *port)
690{
691 struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
692
693 free_irq(bc->tx_irq, bc);
694 free_irq(bc->rx_irq, bc);
695}
696
697static const struct tty_port_operations ehv_bc_tty_port_ops = {
698 .activate = ehv_bc_tty_port_activate,
699 .shutdown = ehv_bc_tty_port_shutdown,
700};
701
702static int __devinit ehv_bc_tty_probe(struct platform_device *pdev)
703{
704 struct device_node *np = pdev->dev.of_node;
705 struct ehv_bc_data *bc;
706 const uint32_t *iprop;
707 unsigned int handle;
708 int ret;
709 static unsigned int index = 1;
710 unsigned int i;
711
712 iprop = of_get_property(np, "hv-handle", NULL);
713 if (!iprop) {
714 dev_err(&pdev->dev, "no 'hv-handle' property in %s node\n",
715 np->name);
716 return -ENODEV;
717 }
718
719 /* We already told the console layer that the index for the console
720 * device is zero, so we need to make sure that we use that index when
721 * we probe the console byte channel node.
722 */
723 handle = be32_to_cpu(*iprop);
724 i = (handle == stdout_bc) ? 0 : index++;
725 bc = &bcs[i];
726
727 bc->handle = handle;
728 bc->head = 0;
729 bc->tail = 0;
730 spin_lock_init(&bc->lock);
731
732 bc->rx_irq = irq_of_parse_and_map(np, 0);
733 bc->tx_irq = irq_of_parse_and_map(np, 1);
734 if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) {
735 dev_err(&pdev->dev, "no 'interrupts' property in %s node\n",
736 np->name);
737 ret = -ENODEV;
738 goto error;
739 }
740
741 bc->dev = tty_register_device(ehv_bc_driver, i, &pdev->dev);
742 if (IS_ERR(bc->dev)) {
743 ret = PTR_ERR(bc->dev);
744 dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
745 goto error;
746 }
747
748 tty_port_init(&bc->port);
749 bc->port.ops = &ehv_bc_tty_port_ops;
750
751 dev_set_drvdata(&pdev->dev, bc);
752
753 dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
754 ehv_bc_driver->name, i, bc->handle);
755
756 return 0;
757
758error:
759 irq_dispose_mapping(bc->tx_irq);
760 irq_dispose_mapping(bc->rx_irq);
761
762 memset(bc, 0, sizeof(struct ehv_bc_data));
763 return ret;
764}
765
766static int ehv_bc_tty_remove(struct platform_device *pdev)
767{
768 struct ehv_bc_data *bc = dev_get_drvdata(&pdev->dev);
769
770 tty_unregister_device(ehv_bc_driver, bc - bcs);
771
772 irq_dispose_mapping(bc->tx_irq);
773 irq_dispose_mapping(bc->rx_irq);
774
775 return 0;
776}
777
778static const struct of_device_id ehv_bc_tty_of_ids[] = {
779 { .compatible = "epapr,hv-byte-channel" },
780 {}
781};
782
783static struct platform_driver ehv_bc_tty_driver = {
784 .driver = {
785 .owner = THIS_MODULE,
786 .name = "ehv-bc",
787 .of_match_table = ehv_bc_tty_of_ids,
788 },
789 .probe = ehv_bc_tty_probe,
790 .remove = ehv_bc_tty_remove,
791};
792
793/**
794 * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
795 *
796 * This function is called when this module is loaded.
797 */
798static int __init ehv_bc_init(void)
799{
800 struct device_node *np;
801 unsigned int count = 0; /* Number of elements in bcs[] */
802 int ret;
803
804 pr_info("ePAPR hypervisor byte channel driver\n");
805
806 /* Count the number of byte channels */
807 for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
808 count++;
809
810 if (!count)
811 return -ENODEV;
812
813 /* The array index of an element in bcs[] is the same as the tty index
814 * for that element. If you know the address of an element in the
815 * array, then you can use pointer math (e.g. "bc - bcs") to get its
816 * tty index.
817 */
818 bcs = kzalloc(count * sizeof(struct ehv_bc_data), GFP_KERNEL);
819 if (!bcs)
820 return -ENOMEM;
821
822 ehv_bc_driver = alloc_tty_driver(count);
823 if (!ehv_bc_driver) {
824 ret = -ENOMEM;
825 goto error;
826 }
827
828 ehv_bc_driver->driver_name = "ehv-bc";
829 ehv_bc_driver->name = ehv_bc_console.name;
830 ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
831 ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
832 ehv_bc_driver->init_termios = tty_std_termios;
833 ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
834 tty_set_operations(ehv_bc_driver, &ehv_bc_ops);
835
836 ret = tty_register_driver(ehv_bc_driver);
837 if (ret) {
838 pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
839 goto error;
840 }
841
842 ret = platform_driver_register(&ehv_bc_tty_driver);
843 if (ret) {
844 pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
845 ret);
846 goto error;
847 }
848
849 return 0;
850
851error:
852 if (ehv_bc_driver) {
853 tty_unregister_driver(ehv_bc_driver);
854 put_tty_driver(ehv_bc_driver);
855 }
856
857 kfree(bcs);
858
859 return ret;
860}
861
862
863/**
864 * ehv_bc_exit - ePAPR hypervisor byte channel driver termination
865 *
866 * This function is called when this driver is unloaded.
867 */
868static void __exit ehv_bc_exit(void)
869{
870 tty_unregister_driver(ehv_bc_driver);
871 put_tty_driver(ehv_bc_driver);
872 kfree(bcs);
873}
874
875module_init(ehv_bc_init);
876module_exit(ehv_bc_exit);
877
878MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
879MODULE_DESCRIPTION("ePAPR hypervisor byte channel driver");
880MODULE_LICENSE("GPL v2");