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