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