xref: /openbmc/linux/drivers/mailbox/pcc.c (revision e2f1cf25)
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/list.h>
63 #include <linux/platform_device.h>
64 #include <linux/mailbox_controller.h>
65 #include <linux/mailbox_client.h>
66 
67 #include "mailbox.h"
68 
69 #define MAX_PCC_SUBSPACES	256
70 
71 static struct mbox_chan *pcc_mbox_channels;
72 
73 static struct mbox_controller pcc_mbox_ctrl = {};
74 /**
75  * get_pcc_channel - Given a PCC subspace idx, get
76  *	the respective mbox_channel.
77  * @id: PCC subspace index.
78  *
79  * Return: ERR_PTR(errno) if error, else pointer
80  *	to mbox channel.
81  */
82 static struct mbox_chan *get_pcc_channel(int id)
83 {
84 	struct mbox_chan *pcc_chan;
85 
86 	if (id < 0 || id > pcc_mbox_ctrl.num_chans)
87 		return ERR_PTR(-ENOENT);
88 
89 	pcc_chan = (struct mbox_chan *)
90 		(unsigned long) pcc_mbox_channels +
91 		(id * sizeof(*pcc_chan));
92 
93 	return pcc_chan;
94 }
95 
96 /**
97  * pcc_mbox_request_channel - PCC clients call this function to
98  *		request a pointer to their PCC subspace, from which they
99  *		can get the details of communicating with the remote.
100  * @cl: Pointer to Mailbox client, so we know where to bind the
101  *		Channel.
102  * @subspace_id: The PCC Subspace index as parsed in the PCC client
103  *		ACPI package. This is used to lookup the array of PCC
104  *		subspaces as parsed by the PCC Mailbox controller.
105  *
106  * Return: Pointer to the Mailbox Channel if successful or
107  *		ERR_PTR.
108  */
109 struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
110 		int subspace_id)
111 {
112 	struct device *dev = pcc_mbox_ctrl.dev;
113 	struct mbox_chan *chan;
114 	unsigned long flags;
115 
116 	/*
117 	 * Each PCC Subspace is a Mailbox Channel.
118 	 * The PCC Clients get their PCC Subspace ID
119 	 * from their own tables and pass it here.
120 	 * This returns a pointer to the PCC subspace
121 	 * for the Client to operate on.
122 	 */
123 	chan = get_pcc_channel(subspace_id);
124 
125 	if (!chan || chan->cl) {
126 		dev_err(dev, "Channel not found for idx: %d\n", subspace_id);
127 		return ERR_PTR(-EBUSY);
128 	}
129 
130 	spin_lock_irqsave(&chan->lock, flags);
131 	chan->msg_free = 0;
132 	chan->msg_count = 0;
133 	chan->active_req = NULL;
134 	chan->cl = cl;
135 	init_completion(&chan->tx_complete);
136 
137 	if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
138 		chan->txdone_method |= TXDONE_BY_ACK;
139 
140 	spin_unlock_irqrestore(&chan->lock, flags);
141 
142 	return chan;
143 }
144 EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
145 
146 /**
147  * pcc_mbox_free_channel - Clients call this to free their Channel.
148  *
149  * @chan: Pointer to the mailbox channel as returned by
150  *		pcc_mbox_request_channel()
151  */
152 void pcc_mbox_free_channel(struct mbox_chan *chan)
153 {
154 	unsigned long flags;
155 
156 	if (!chan || !chan->cl)
157 		return;
158 
159 	spin_lock_irqsave(&chan->lock, flags);
160 	chan->cl = NULL;
161 	chan->active_req = NULL;
162 	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
163 		chan->txdone_method = TXDONE_BY_POLL;
164 
165 	spin_unlock_irqrestore(&chan->lock, flags);
166 }
167 EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
168 
169 /**
170  * pcc_send_data - Called from Mailbox Controller code. Used
171  *		here only to ring the channel doorbell. The PCC client
172  *		specific read/write is done in the client driver in
173  *		order to maintain atomicity over PCC channel once
174  *		OS has control over it. See above for flow of operations.
175  * @chan: Pointer to Mailbox channel over which to send data.
176  * @data: Client specific data written over channel. Used here
177  *		only for debug after PCC transaction completes.
178  *
179  * Return: Err if something failed else 0 for success.
180  */
181 static int pcc_send_data(struct mbox_chan *chan, void *data)
182 {
183 	struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv;
184 	struct acpi_generic_address doorbell;
185 	u64 doorbell_preserve;
186 	u64 doorbell_val;
187 	u64 doorbell_write;
188 
189 	doorbell = pcct_ss->doorbell_register;
190 	doorbell_preserve = pcct_ss->preserve_mask;
191 	doorbell_write = pcct_ss->write_mask;
192 
193 	/* Sync notification from OS to Platform. */
194 	acpi_read(&doorbell_val, &doorbell);
195 	acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
196 			&doorbell);
197 
198 	return 0;
199 }
200 
201 static const struct mbox_chan_ops pcc_chan_ops = {
202 	.send_data = pcc_send_data,
203 };
204 
205 /**
206  * parse_pcc_subspace - Parse the PCC table and verify PCC subspace
207  *		entries. There should be one entry per PCC client.
208  * @header: Pointer to the ACPI subtable header under the PCCT.
209  * @end: End of subtable entry.
210  *
211  * Return: 0 for Success, else errno.
212  *
213  * This gets called for each entry in the PCC table.
214  */
215 static int parse_pcc_subspace(struct acpi_subtable_header *header,
216 		const unsigned long end)
217 {
218 	struct acpi_pcct_hw_reduced *pcct_ss;
219 
220 	if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
221 		pcct_ss = (struct acpi_pcct_hw_reduced *) header;
222 
223 		if (pcct_ss->header.type !=
224 				ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE) {
225 			pr_err("Incorrect PCC Subspace type detected\n");
226 			return -EINVAL;
227 		}
228 	}
229 
230 	return 0;
231 }
232 
233 /**
234  * acpi_pcc_probe - Parse the ACPI tree for the PCCT.
235  *
236  * Return: 0 for Success, else errno.
237  */
238 static int __init acpi_pcc_probe(void)
239 {
240 	acpi_size pcct_tbl_header_size;
241 	struct acpi_table_header *pcct_tbl;
242 	struct acpi_subtable_header *pcct_entry;
243 	int count, i;
244 	acpi_status status = AE_OK;
245 
246 	/* Search for PCCT */
247 	status = acpi_get_table_with_size(ACPI_SIG_PCCT, 0,
248 			&pcct_tbl,
249 			&pcct_tbl_header_size);
250 
251 	if (ACPI_FAILURE(status) || !pcct_tbl) {
252 		pr_warn("PCCT header not found.\n");
253 		return -ENODEV;
254 	}
255 
256 	count = acpi_table_parse_entries(ACPI_SIG_PCCT,
257 			sizeof(struct acpi_table_pcct),
258 			ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE,
259 			parse_pcc_subspace, MAX_PCC_SUBSPACES);
260 
261 	if (count <= 0) {
262 		pr_err("Error parsing PCC subspaces from PCCT\n");
263 		return -EINVAL;
264 	}
265 
266 	pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) *
267 			count, GFP_KERNEL);
268 
269 	if (!pcc_mbox_channels) {
270 		pr_err("Could not allocate space for PCC mbox channels\n");
271 		return -ENOMEM;
272 	}
273 
274 	/* Point to the first PCC subspace entry */
275 	pcct_entry = (struct acpi_subtable_header *) (
276 		(unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct));
277 
278 	for (i = 0; i < count; i++) {
279 		pcc_mbox_channels[i].con_priv = pcct_entry;
280 		pcct_entry = (struct acpi_subtable_header *)
281 			((unsigned long) pcct_entry + pcct_entry->length);
282 	}
283 
284 	pcc_mbox_ctrl.num_chans = count;
285 
286 	pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);
287 
288 	return 0;
289 }
290 
291 /**
292  * pcc_mbox_probe - Called when we find a match for the
293  *	PCCT platform device. This is purely used to represent
294  *	the PCCT as a virtual device for registering with the
295  *	generic Mailbox framework.
296  *
297  * @pdev: Pointer to platform device returned when a match
298  *	is found.
299  *
300  *	Return: 0 for Success, else errno.
301  */
302 static int pcc_mbox_probe(struct platform_device *pdev)
303 {
304 	int ret = 0;
305 
306 	pcc_mbox_ctrl.chans = pcc_mbox_channels;
307 	pcc_mbox_ctrl.ops = &pcc_chan_ops;
308 	pcc_mbox_ctrl.dev = &pdev->dev;
309 
310 	pr_info("Registering PCC driver as Mailbox controller\n");
311 	ret = mbox_controller_register(&pcc_mbox_ctrl);
312 
313 	if (ret) {
314 		pr_err("Err registering PCC as Mailbox controller: %d\n", ret);
315 		ret = -ENODEV;
316 	}
317 
318 	return ret;
319 }
320 
321 struct platform_driver pcc_mbox_driver = {
322 	.probe = pcc_mbox_probe,
323 	.driver = {
324 		.name = "PCCT",
325 		.owner = THIS_MODULE,
326 	},
327 };
328 
329 static int __init pcc_init(void)
330 {
331 	int ret;
332 	struct platform_device *pcc_pdev;
333 
334 	if (acpi_disabled)
335 		return -ENODEV;
336 
337 	/* Check if PCC support is available. */
338 	ret = acpi_pcc_probe();
339 
340 	if (ret) {
341 		pr_debug("ACPI PCC probe failed.\n");
342 		return -ENODEV;
343 	}
344 
345 	pcc_pdev = platform_create_bundle(&pcc_mbox_driver,
346 			pcc_mbox_probe, NULL, 0, NULL, 0);
347 
348 	if (IS_ERR(pcc_pdev)) {
349 		pr_debug("Err creating PCC platform bundle\n");
350 		return PTR_ERR(pcc_pdev);
351 	}
352 
353 	return 0;
354 }
355 device_initcall(pcc_init);
356