1/*
  2 *	Copyright (C) 2014 Linaro Ltd.
  3 *	Author:	Ashwin Chaugule <ashwin.chaugule@linaro.org>
  4 *
  5 *  This program is free software; you can redistribute it and/or modify
  6 *  it under the terms of the GNU General Public License as published by
  7 *  the Free Software Foundation; either version 2 of the License, or
  8 *  (at your option) any later version.
  9 *
 10 *  This program is distributed in the hope that it will be useful,
 11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 13 *  GNU General Public License for more details.
 14 *
 15 *  PCC (Platform Communication Channel) is defined in the ACPI 5.0+
 16 *  specification. It is a mailbox like mechanism to allow clients
 17 *  such as CPPC (Collaborative Processor Performance Control), RAS
 18 *  (Reliability, Availability and Serviceability) and MPST (Memory
 19 *  Node Power State Table) to talk to the platform (e.g. BMC) through
 20 *  shared memory regions as defined in the PCC table entries. The PCC
 21 *  specification supports a Doorbell mechanism for the PCC clients
 22 *  to notify the platform about new data. This Doorbell information
 23 *  is also specified in each PCC table entry.
 24 *
 25 *  Typical high level flow of operation is:
 26 *
 27 *  PCC Reads:
 28 *  * Client tries to acquire a channel lock.
 29 *  * After it is acquired it writes READ cmd in communication region cmd
 30 *		address.
 31 *  * Client issues mbox_send_message() which rings the PCC doorbell
 32 *		for its PCC channel.
 33 *  * If command completes, then client has control over channel and
 34 *		it can proceed with its reads.
 35 *  * Client releases lock.
 36 *
 37 *  PCC Writes:
 38 *  * Client tries to acquire channel lock.
 39 *  * Client writes to its communication region after it acquires a
 40 *		channel lock.
 41 *  * Client writes WRITE cmd in communication region cmd address.
 42 *  * Client issues mbox_send_message() which rings the PCC doorbell
 43 *		for its PCC channel.
 44 *  * If command completes, then writes have succeded and it can release
 45 *		the channel lock.
 46 *
 47 *  There is a Nominal latency defined for each channel which indicates
 48 *  how long to wait until a command completes. If command is not complete
 49 *  the client needs to retry or assume failure.
 50 *
 51 *	For more details about PCC, please see the ACPI specification from
 52 *  http://www.uefi.org/ACPIv5.1 Section 14.
 53 *
 54 *  This file implements PCC as a Mailbox controller and allows for PCC
 55 *  clients to be implemented as its Mailbox Client Channels.
 56 */
 57
 58#include <linux/acpi.h>
 59#include <linux/delay.h>
 60#include <linux/io.h>
 61#include <linux/init.h>
 62#include <linux/interrupt.h>
 63#include <linux/list.h>
 64#include <linux/platform_device.h>
 65#include <linux/mailbox_controller.h>
 66#include <linux/mailbox_client.h>
 67#include <linux/io-64-nonatomic-lo-hi.h>
 68#include <acpi/pcc.h>
 69
 70#include "mailbox.h"
 71
 72#define MAX_PCC_SUBSPACES	256
 73#define MBOX_IRQ_NAME		"pcc-mbox"
 74
 75static struct mbox_chan *pcc_mbox_channels;
 76
 77/* Array of cached virtual address for doorbell registers */
 78static void __iomem **pcc_doorbell_vaddr;
 79/* Array of cached virtual address for doorbell ack registers */
 80static void __iomem **pcc_doorbell_ack_vaddr;
 81/* Array of doorbell interrupts */
 82static int *pcc_doorbell_irq;
 83
 84static struct mbox_controller pcc_mbox_ctrl = {};
 85/**
 86 * get_pcc_channel - Given a PCC subspace idx, get
 87 *	the respective mbox_channel.
 88 * @id: PCC subspace index.
 89 *
 90 * Return: ERR_PTR(errno) if error, else pointer
 91 *	to mbox channel.
 92 */
 93static struct mbox_chan *get_pcc_channel(int id)
 94{
 95	if (id < 0 || id > pcc_mbox_ctrl.num_chans)
 96		return ERR_PTR(-ENOENT);
 97
 98	return &pcc_mbox_channels[id];
 99}
100
101/*
102 * PCC can be used with perf critical drivers such as CPPC
103 * So it makes sense to locally cache the virtual address and
104 * use it to read/write to PCC registers such as doorbell register
105 *
106 * The below read_register and write_registers are used to read and
107 * write from perf critical registers such as PCC doorbell register
108 */
109static int read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width)
110{
111	int ret_val = 0;
112
113	switch (bit_width) {
114	case 8:
115		*val = readb(vaddr);
116		break;
117	case 16:
118		*val = readw(vaddr);
119		break;
120	case 32:
121		*val = readl(vaddr);
122		break;
123	case 64:
124		*val = readq(vaddr);
125		break;
126	default:
127		pr_debug("Error: Cannot read register of %u bit width",
128			bit_width);
129		ret_val = -EFAULT;
130		break;
131	}
132	return ret_val;
133}
134
135static int write_register(void __iomem *vaddr, u64 val, unsigned int bit_width)
136{
137	int ret_val = 0;
138
139	switch (bit_width) {
140	case 8:
141		writeb(val, vaddr);
142		break;
143	case 16:
144		writew(val, vaddr);
145		break;
146	case 32:
147		writel(val, vaddr);
148		break;
149	case 64:
150		writeq(val, vaddr);
151		break;
152	default:
153		pr_debug("Error: Cannot write register of %u bit width",
154			bit_width);
155		ret_val = -EFAULT;
156		break;
157	}
158	return ret_val;
159}
160
161/**
162 * pcc_map_interrupt - Map a PCC subspace GSI to a linux IRQ number
163 * @interrupt: GSI number.
164 * @flags: interrupt flags
165 *
166 * Returns: a valid linux IRQ number on success
167 *		0 or -EINVAL on failure
168 */
169static int pcc_map_interrupt(u32 interrupt, u32 flags)
170{
171	int trigger, polarity;
172
173	if (!interrupt)
174		return 0;
175
176	trigger = (flags & ACPI_PCCT_INTERRUPT_MODE) ? ACPI_EDGE_SENSITIVE
177			: ACPI_LEVEL_SENSITIVE;
178
179	polarity = (flags & ACPI_PCCT_INTERRUPT_POLARITY) ? ACPI_ACTIVE_LOW
180			: ACPI_ACTIVE_HIGH;
181
182	return acpi_register_gsi(NULL, interrupt, trigger, polarity);
183}
184
185/**
186 * pcc_mbox_irq - PCC mailbox interrupt handler
187 */
188static irqreturn_t pcc_mbox_irq(int irq, void *p)
189{
190	struct acpi_generic_address *doorbell_ack;
191	struct acpi_pcct_hw_reduced *pcct_ss;
192	struct mbox_chan *chan = p;
193	u64 doorbell_ack_preserve;
194	u64 doorbell_ack_write;
195	u64 doorbell_ack_val;
196	int ret;
197
198	pcct_ss = chan->con_priv;
199
200	mbox_chan_received_data(chan, NULL);
201
202	if (pcct_ss->header.type == ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
203		struct acpi_pcct_hw_reduced_type2 *pcct2_ss = chan->con_priv;
204		u32 id = chan - pcc_mbox_channels;
205
206		doorbell_ack = &pcct2_ss->doorbell_ack_register;
207		doorbell_ack_preserve = pcct2_ss->ack_preserve_mask;
208		doorbell_ack_write = pcct2_ss->ack_write_mask;
209
210		ret = read_register(pcc_doorbell_ack_vaddr[id],
211				    &doorbell_ack_val,
212				    doorbell_ack->bit_width);
213		if (ret)
214			return IRQ_NONE;
215
216		ret = write_register(pcc_doorbell_ack_vaddr[id],
217				     (doorbell_ack_val & doorbell_ack_preserve)
218					| doorbell_ack_write,
219				     doorbell_ack->bit_width);
220		if (ret)
221			return IRQ_NONE;
222	}
223
224	return IRQ_HANDLED;
225}
226
227/**
228 * pcc_mbox_request_channel - PCC clients call this function to
229 *		request a pointer to their PCC subspace, from which they
230 *		can get the details of communicating with the remote.
231 * @cl: Pointer to Mailbox client, so we know where to bind the
232 *		Channel.
233 * @subspace_id: The PCC Subspace index as parsed in the PCC client
234 *		ACPI package. This is used to lookup the array of PCC
235 *		subspaces as parsed by the PCC Mailbox controller.
236 *
237 * Return: Pointer to the Mailbox Channel if successful or
238 *		ERR_PTR.
239 */
240struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
241		int subspace_id)
242{
243	struct device *dev = pcc_mbox_ctrl.dev;
244	struct mbox_chan *chan;
245	unsigned long flags;
246
247	/*
248	 * Each PCC Subspace is a Mailbox Channel.
249	 * The PCC Clients get their PCC Subspace ID
250	 * from their own tables and pass it here.
251	 * This returns a pointer to the PCC subspace
252	 * for the Client to operate on.
253	 */
254	chan = get_pcc_channel(subspace_id);
255
256	if (IS_ERR(chan) || chan->cl) {
257		dev_err(dev, "Channel not found for idx: %d\n", subspace_id);
258		return ERR_PTR(-EBUSY);
259	}
260
261	spin_lock_irqsave(&chan->lock, flags);
262	chan->msg_free = 0;
263	chan->msg_count = 0;
264	chan->active_req = NULL;
265	chan->cl = cl;
266	init_completion(&chan->tx_complete);
267
268	if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
269		chan->txdone_method |= TXDONE_BY_ACK;
270
271	spin_unlock_irqrestore(&chan->lock, flags);
272
273	if (pcc_doorbell_irq[subspace_id] > 0) {
274		int rc;
275
276		rc = devm_request_irq(dev, pcc_doorbell_irq[subspace_id],
277				      pcc_mbox_irq, 0, MBOX_IRQ_NAME, chan);
278		if (unlikely(rc)) {
279			dev_err(dev, "failed to register PCC interrupt %d\n",
280				pcc_doorbell_irq[subspace_id]);
281			pcc_mbox_free_channel(chan);
282			chan = ERR_PTR(rc);
283		}
284	}
285
286	return chan;
287}
288EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
289
290/**
291 * pcc_mbox_free_channel - Clients call this to free their Channel.
292 *
293 * @chan: Pointer to the mailbox channel as returned by
294 *		pcc_mbox_request_channel()
295 */
296void pcc_mbox_free_channel(struct mbox_chan *chan)
297{
298	u32 id = chan - pcc_mbox_channels;
299	unsigned long flags;
300
301	if (!chan || !chan->cl)
302		return;
303
304	if (id >= pcc_mbox_ctrl.num_chans) {
305		pr_debug("pcc_mbox_free_channel: Invalid mbox_chan passed\n");
306		return;
307	}
308
309	if (pcc_doorbell_irq[id] > 0)
310		devm_free_irq(chan->mbox->dev, pcc_doorbell_irq[id], chan);
311
312	spin_lock_irqsave(&chan->lock, flags);
313	chan->cl = NULL;
314	chan->active_req = NULL;
315	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
316		chan->txdone_method = TXDONE_BY_POLL;
317
318	spin_unlock_irqrestore(&chan->lock, flags);
319}
320EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
321
322/**
323 * pcc_send_data - Called from Mailbox Controller code. Used
324 *		here only to ring the channel doorbell. The PCC client
325 *		specific read/write is done in the client driver in
326 *		order to maintain atomicity over PCC channel once
327 *		OS has control over it. See above for flow of operations.
328 * @chan: Pointer to Mailbox channel over which to send data.
329 * @data: Client specific data written over channel. Used here
330 *		only for debug after PCC transaction completes.
331 *
332 * Return: Err if something failed else 0 for success.
333 */
334static int pcc_send_data(struct mbox_chan *chan, void *data)
335{
336	struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv;
337	struct acpi_generic_address *doorbell;
338	u64 doorbell_preserve;
339	u64 doorbell_val;
340	u64 doorbell_write;
341	u32 id = chan - pcc_mbox_channels;
342	int ret = 0;
343
344	if (id >= pcc_mbox_ctrl.num_chans) {
345		pr_debug("pcc_send_data: Invalid mbox_chan passed\n");
346		return -ENOENT;
347	}
348
349	doorbell = &pcct_ss->doorbell_register;
350	doorbell_preserve = pcct_ss->preserve_mask;
351	doorbell_write = pcct_ss->write_mask;
352
353	/* Sync notification from OS to Platform. */
354	if (pcc_doorbell_vaddr[id]) {
355		ret = read_register(pcc_doorbell_vaddr[id], &doorbell_val,
356			doorbell->bit_width);
357		if (ret)
358			return ret;
359		ret = write_register(pcc_doorbell_vaddr[id],
360			(doorbell_val & doorbell_preserve) | doorbell_write,
361			doorbell->bit_width);
362	} else {
363		ret = acpi_read(&doorbell_val, doorbell);
364		if (ret)
365			return ret;
366		ret = acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
367			doorbell);
368	}
369	return ret;
370}
371
372static const struct mbox_chan_ops pcc_chan_ops = {
373	.send_data = pcc_send_data,
374};
375
376/**
377 * parse_pcc_subspace - Parse the PCC table and verify PCC subspace
378 *		entries. There should be one entry per PCC client.
379 * @header: Pointer to the ACPI subtable header under the PCCT.
380 * @end: End of subtable entry.
381 *
382 * Return: 0 for Success, else errno.
383 *
384 * This gets called for each entry in the PCC table.
385 */
386static int parse_pcc_subspace(struct acpi_subtable_header *header,
387		const unsigned long end)
388{
389	struct acpi_pcct_hw_reduced *pcct_ss;
390
391	if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
392		pcct_ss = (struct acpi_pcct_hw_reduced *) header;
393
394		if ((pcct_ss->header.type !=
395				ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE)
396		    && (pcct_ss->header.type !=
397				ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2)) {
398			pr_err("Incorrect PCC Subspace type detected\n");
399			return -EINVAL;
400		}
401	}
402
403	return 0;
404}
405
406/**
407 * pcc_parse_subspace_irq - Parse the PCC IRQ and PCC ACK register
408 *		There should be one entry per PCC client.
409 * @id: PCC subspace index.
410 * @pcct_ss: Pointer to the ACPI subtable header under the PCCT.
411 *
412 * Return: 0 for Success, else errno.
413 *
414 * This gets called for each entry in the PCC table.
415 */
416static int pcc_parse_subspace_irq(int id,
417				  struct acpi_pcct_hw_reduced *pcct_ss)
418{
419	pcc_doorbell_irq[id] = pcc_map_interrupt(pcct_ss->doorbell_interrupt,
420						 (u32)pcct_ss->flags);
421	if (pcc_doorbell_irq[id] <= 0) {
422		pr_err("PCC GSI %d not registered\n",
423		       pcct_ss->doorbell_interrupt);
424		return -EINVAL;
425	}
426
427	if (pcct_ss->header.type
428		== ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
429		struct acpi_pcct_hw_reduced_type2 *pcct2_ss = (void *)pcct_ss;
430
431		pcc_doorbell_ack_vaddr[id] = acpi_os_ioremap(
432				pcct2_ss->doorbell_ack_register.address,
433				pcct2_ss->doorbell_ack_register.bit_width / 8);
434		if (!pcc_doorbell_ack_vaddr[id]) {
435			pr_err("Failed to ioremap PCC ACK register\n");
436			return -ENOMEM;
437		}
438	}
439
440	return 0;
441}
442
443/**
444 * acpi_pcc_probe - Parse the ACPI tree for the PCCT.
445 *
446 * Return: 0 for Success, else errno.
447 */
448static int __init acpi_pcc_probe(void)
449{
450	struct acpi_table_header *pcct_tbl;
451	struct acpi_subtable_header *pcct_entry;
452	struct acpi_table_pcct *acpi_pcct_tbl;
453	int count, i, rc;
454	int sum = 0;
455	acpi_status status = AE_OK;
456
457	/* Search for PCCT */
458	status = acpi_get_table(ACPI_SIG_PCCT, 0, &pcct_tbl);
459
460	if (ACPI_FAILURE(status) || !pcct_tbl) {
461		pr_warn("PCCT header not found.\n");
462		return -ENODEV;
463	}
464
465	count = acpi_table_parse_entries(ACPI_SIG_PCCT,
466			sizeof(struct acpi_table_pcct),
467			ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE,
468			parse_pcc_subspace, MAX_PCC_SUBSPACES);
469	sum += (count > 0) ? count : 0;
470
471	count = acpi_table_parse_entries(ACPI_SIG_PCCT,
472			sizeof(struct acpi_table_pcct),
473			ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2,
474			parse_pcc_subspace, MAX_PCC_SUBSPACES);
475	sum += (count > 0) ? count : 0;
476
477	if (sum == 0 || sum >= MAX_PCC_SUBSPACES) {
478		pr_err("Error parsing PCC subspaces from PCCT\n");
479		return -EINVAL;
480	}
481
482	pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) *
483			sum, GFP_KERNEL);
484	if (!pcc_mbox_channels) {
485		pr_err("Could not allocate space for PCC mbox channels\n");
486		return -ENOMEM;
487	}
488
489	pcc_doorbell_vaddr = kcalloc(sum, sizeof(void *), GFP_KERNEL);
490	if (!pcc_doorbell_vaddr) {
491		rc = -ENOMEM;
492		goto err_free_mbox;
493	}
494
495	pcc_doorbell_ack_vaddr = kcalloc(sum, sizeof(void *), GFP_KERNEL);
496	if (!pcc_doorbell_ack_vaddr) {
497		rc = -ENOMEM;
498		goto err_free_db_vaddr;
499	}
500
501	pcc_doorbell_irq = kcalloc(sum, sizeof(int), GFP_KERNEL);
502	if (!pcc_doorbell_irq) {
503		rc = -ENOMEM;
504		goto err_free_db_ack_vaddr;
505	}
506
507	/* Point to the first PCC subspace entry */
508	pcct_entry = (struct acpi_subtable_header *) (
509		(unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct));
510
511	acpi_pcct_tbl = (struct acpi_table_pcct *) pcct_tbl;
512	if (acpi_pcct_tbl->flags & ACPI_PCCT_DOORBELL)
513		pcc_mbox_ctrl.txdone_irq = true;
514
515	for (i = 0; i < sum; i++) {
516		struct acpi_generic_address *db_reg;
517		struct acpi_pcct_hw_reduced *pcct_ss;
518		pcc_mbox_channels[i].con_priv = pcct_entry;
519
520		pcct_ss = (struct acpi_pcct_hw_reduced *) pcct_entry;
521
522		if (pcc_mbox_ctrl.txdone_irq) {
523			rc = pcc_parse_subspace_irq(i, pcct_ss);
524			if (rc < 0)
525				goto err;
526		}
527
528		/* If doorbell is in system memory cache the virt address */
529		db_reg = &pcct_ss->doorbell_register;
530		if (db_reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
531			pcc_doorbell_vaddr[i] = acpi_os_ioremap(db_reg->address,
532							db_reg->bit_width/8);
533		pcct_entry = (struct acpi_subtable_header *)
534			((unsigned long) pcct_entry + pcct_entry->length);
535	}
536
537	pcc_mbox_ctrl.num_chans = sum;
538
539	pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);
540
541	return 0;
542
543err:
544	kfree(pcc_doorbell_irq);
545err_free_db_ack_vaddr:
546	kfree(pcc_doorbell_ack_vaddr);
547err_free_db_vaddr:
548	kfree(pcc_doorbell_vaddr);
549err_free_mbox:
550	kfree(pcc_mbox_channels);
551	return rc;
552}
553
554/**
555 * pcc_mbox_probe - Called when we find a match for the
556 *	PCCT platform device. This is purely used to represent
557 *	the PCCT as a virtual device for registering with the
558 *	generic Mailbox framework.
559 *
560 * @pdev: Pointer to platform device returned when a match
561 *	is found.
562 *
563 *	Return: 0 for Success, else errno.
564 */
565static int pcc_mbox_probe(struct platform_device *pdev)
566{
567	int ret = 0;
568
569	pcc_mbox_ctrl.chans = pcc_mbox_channels;
570	pcc_mbox_ctrl.ops = &pcc_chan_ops;
571	pcc_mbox_ctrl.dev = &pdev->dev;
572
573	pr_info("Registering PCC driver as Mailbox controller\n");
574	ret = mbox_controller_register(&pcc_mbox_ctrl);
575
576	if (ret) {
577		pr_err("Err registering PCC as Mailbox controller: %d\n", ret);
578		ret = -ENODEV;
579	}
580
581	return ret;
582}
583
584struct platform_driver pcc_mbox_driver = {
585	.probe = pcc_mbox_probe,
586	.driver = {
587		.name = "PCCT",
588		.owner = THIS_MODULE,
589	},
590};
591
592static int __init pcc_init(void)
593{
594	int ret;
595	struct platform_device *pcc_pdev;
596
597	if (acpi_disabled)
598		return -ENODEV;
599
600	/* Check if PCC support is available. */
601	ret = acpi_pcc_probe();
602
603	if (ret) {
604		pr_debug("ACPI PCC probe failed.\n");
605		return -ENODEV;
606	}
607
608	pcc_pdev = platform_create_bundle(&pcc_mbox_driver,
609			pcc_mbox_probe, NULL, 0, NULL, 0);
610
611	if (IS_ERR(pcc_pdev)) {
612		pr_debug("Err creating PCC platform bundle\n");
613		return PTR_ERR(pcc_pdev);
614	}
615
616	return 0;
617}
618
619/*
620 * Make PCC init postcore so that users of this mailbox
621 * such as the ACPI Processor driver have it available
622 * at their init.
623 */
624postcore_initcall(pcc_init);