drivers/mailbox/pcc.c

   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 (IS_ERR(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
 356 /*
 357  * Make PCC init postcore so that users of this mailbox
 358  * such as the ACPI Processor driver have it available
 359  * at their init.
 360  */
 361 postcore_initcall(pcc_init);