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 #include <linux/io-64-nonatomic-lo-hi.h> 67 68 #include "mailbox.h" 69 70 #define MAX_PCC_SUBSPACES 256 71 72 static struct mbox_chan *pcc_mbox_channels; 73 74 /* Array of cached virtual address for doorbell registers */ 75 static void __iomem **pcc_doorbell_vaddr; 76 77 static struct mbox_controller pcc_mbox_ctrl = {}; 78 /** 79 * get_pcc_channel - Given a PCC subspace idx, get 80 * the respective mbox_channel. 81 * @id: PCC subspace index. 82 * 83 * Return: ERR_PTR(errno) if error, else pointer 84 * to mbox channel. 85 */ 86 static struct mbox_chan *get_pcc_channel(int id) 87 { 88 if (id < 0 || id > pcc_mbox_ctrl.num_chans) 89 return ERR_PTR(-ENOENT); 90 91 return &pcc_mbox_channels[id]; 92 } 93 94 /** 95 * pcc_mbox_request_channel - PCC clients call this function to 96 * request a pointer to their PCC subspace, from which they 97 * can get the details of communicating with the remote. 98 * @cl: Pointer to Mailbox client, so we know where to bind the 99 * Channel. 100 * @subspace_id: The PCC Subspace index as parsed in the PCC client 101 * ACPI package. This is used to lookup the array of PCC 102 * subspaces as parsed by the PCC Mailbox controller. 103 * 104 * Return: Pointer to the Mailbox Channel if successful or 105 * ERR_PTR. 106 */ 107 struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl, 108 int subspace_id) 109 { 110 struct device *dev = pcc_mbox_ctrl.dev; 111 struct mbox_chan *chan; 112 unsigned long flags; 113 114 /* 115 * Each PCC Subspace is a Mailbox Channel. 116 * The PCC Clients get their PCC Subspace ID 117 * from their own tables and pass it here. 118 * This returns a pointer to the PCC subspace 119 * for the Client to operate on. 120 */ 121 chan = get_pcc_channel(subspace_id); 122 123 if (IS_ERR(chan) || chan->cl) { 124 dev_err(dev, "Channel not found for idx: %d\n", subspace_id); 125 return ERR_PTR(-EBUSY); 126 } 127 128 spin_lock_irqsave(&chan->lock, flags); 129 chan->msg_free = 0; 130 chan->msg_count = 0; 131 chan->active_req = NULL; 132 chan->cl = cl; 133 init_completion(&chan->tx_complete); 134 135 if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone) 136 chan->txdone_method |= TXDONE_BY_ACK; 137 138 spin_unlock_irqrestore(&chan->lock, flags); 139 140 return chan; 141 } 142 EXPORT_SYMBOL_GPL(pcc_mbox_request_channel); 143 144 /** 145 * pcc_mbox_free_channel - Clients call this to free their Channel. 146 * 147 * @chan: Pointer to the mailbox channel as returned by 148 * pcc_mbox_request_channel() 149 */ 150 void pcc_mbox_free_channel(struct mbox_chan *chan) 151 { 152 unsigned long flags; 153 154 if (!chan || !chan->cl) 155 return; 156 157 spin_lock_irqsave(&chan->lock, flags); 158 chan->cl = NULL; 159 chan->active_req = NULL; 160 if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK)) 161 chan->txdone_method = TXDONE_BY_POLL; 162 163 spin_unlock_irqrestore(&chan->lock, flags); 164 } 165 EXPORT_SYMBOL_GPL(pcc_mbox_free_channel); 166 167 /* 168 * PCC can be used with perf critical drivers such as CPPC 169 * So it makes sense to locally cache the virtual address and 170 * use it to read/write to PCC registers such as doorbell register 171 * 172 * The below read_register and write_registers are used to read and 173 * write from perf critical registers such as PCC doorbell register 174 */ 175 static int read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width) 176 { 177 int ret_val = 0; 178 179 switch (bit_width) { 180 case 8: 181 *val = readb(vaddr); 182 break; 183 case 16: 184 *val = readw(vaddr); 185 break; 186 case 32: 187 *val = readl(vaddr); 188 break; 189 case 64: 190 *val = readq(vaddr); 191 break; 192 default: 193 pr_debug("Error: Cannot read register of %u bit width", 194 bit_width); 195 ret_val = -EFAULT; 196 break; 197 } 198 return ret_val; 199 } 200 201 static int write_register(void __iomem *vaddr, u64 val, unsigned int bit_width) 202 { 203 int ret_val = 0; 204 205 switch (bit_width) { 206 case 8: 207 writeb(val, vaddr); 208 break; 209 case 16: 210 writew(val, vaddr); 211 break; 212 case 32: 213 writel(val, vaddr); 214 break; 215 case 64: 216 writeq(val, vaddr); 217 break; 218 default: 219 pr_debug("Error: Cannot write register of %u bit width", 220 bit_width); 221 ret_val = -EFAULT; 222 break; 223 } 224 return ret_val; 225 } 226 227 /** 228 * pcc_send_data - Called from Mailbox Controller code. Used 229 * here only to ring the channel doorbell. The PCC client 230 * specific read/write is done in the client driver in 231 * order to maintain atomicity over PCC channel once 232 * OS has control over it. See above for flow of operations. 233 * @chan: Pointer to Mailbox channel over which to send data. 234 * @data: Client specific data written over channel. Used here 235 * only for debug after PCC transaction completes. 236 * 237 * Return: Err if something failed else 0 for success. 238 */ 239 static int pcc_send_data(struct mbox_chan *chan, void *data) 240 { 241 struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv; 242 struct acpi_generic_address *doorbell; 243 u64 doorbell_preserve; 244 u64 doorbell_val; 245 u64 doorbell_write; 246 u32 id = chan - pcc_mbox_channels; 247 int ret = 0; 248 249 if (id >= pcc_mbox_ctrl.num_chans) { 250 pr_debug("pcc_send_data: Invalid mbox_chan passed\n"); 251 return -ENOENT; 252 } 253 254 doorbell = &pcct_ss->doorbell_register; 255 doorbell_preserve = pcct_ss->preserve_mask; 256 doorbell_write = pcct_ss->write_mask; 257 258 /* Sync notification from OS to Platform. */ 259 if (pcc_doorbell_vaddr[id]) { 260 ret = read_register(pcc_doorbell_vaddr[id], &doorbell_val, 261 doorbell->bit_width); 262 if (ret) 263 return ret; 264 ret = write_register(pcc_doorbell_vaddr[id], 265 (doorbell_val & doorbell_preserve) | doorbell_write, 266 doorbell->bit_width); 267 } else { 268 ret = acpi_read(&doorbell_val, doorbell); 269 if (ret) 270 return ret; 271 ret = acpi_write((doorbell_val & doorbell_preserve) | doorbell_write, 272 doorbell); 273 } 274 return ret; 275 } 276 277 static const struct mbox_chan_ops pcc_chan_ops = { 278 .send_data = pcc_send_data, 279 }; 280 281 /** 282 * parse_pcc_subspace - Parse the PCC table and verify PCC subspace 283 * entries. There should be one entry per PCC client. 284 * @header: Pointer to the ACPI subtable header under the PCCT. 285 * @end: End of subtable entry. 286 * 287 * Return: 0 for Success, else errno. 288 * 289 * This gets called for each entry in the PCC table. 290 */ 291 static int parse_pcc_subspace(struct acpi_subtable_header *header, 292 const unsigned long end) 293 { 294 struct acpi_pcct_hw_reduced *pcct_ss; 295 296 if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) { 297 pcct_ss = (struct acpi_pcct_hw_reduced *) header; 298 299 if (pcct_ss->header.type != 300 ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE) { 301 pr_err("Incorrect PCC Subspace type detected\n"); 302 return -EINVAL; 303 } 304 } 305 306 return 0; 307 } 308 309 /** 310 * acpi_pcc_probe - Parse the ACPI tree for the PCCT. 311 * 312 * Return: 0 for Success, else errno. 313 */ 314 static int __init acpi_pcc_probe(void) 315 { 316 acpi_size pcct_tbl_header_size; 317 struct acpi_table_header *pcct_tbl; 318 struct acpi_subtable_header *pcct_entry; 319 int count, i; 320 acpi_status status = AE_OK; 321 322 /* Search for PCCT */ 323 status = acpi_get_table_with_size(ACPI_SIG_PCCT, 0, 324 &pcct_tbl, 325 &pcct_tbl_header_size); 326 327 if (ACPI_FAILURE(status) || !pcct_tbl) { 328 pr_warn("PCCT header not found.\n"); 329 return -ENODEV; 330 } 331 332 count = acpi_table_parse_entries(ACPI_SIG_PCCT, 333 sizeof(struct acpi_table_pcct), 334 ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE, 335 parse_pcc_subspace, MAX_PCC_SUBSPACES); 336 337 if (count <= 0) { 338 pr_err("Error parsing PCC subspaces from PCCT\n"); 339 return -EINVAL; 340 } 341 342 pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) * 343 count, GFP_KERNEL); 344 345 if (!pcc_mbox_channels) { 346 pr_err("Could not allocate space for PCC mbox channels\n"); 347 return -ENOMEM; 348 } 349 350 pcc_doorbell_vaddr = kcalloc(count, sizeof(void *), GFP_KERNEL); 351 if (!pcc_doorbell_vaddr) { 352 kfree(pcc_mbox_channels); 353 return -ENOMEM; 354 } 355 356 /* Point to the first PCC subspace entry */ 357 pcct_entry = (struct acpi_subtable_header *) ( 358 (unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct)); 359 360 for (i = 0; i < count; i++) { 361 struct acpi_generic_address *db_reg; 362 struct acpi_pcct_hw_reduced *pcct_ss; 363 pcc_mbox_channels[i].con_priv = pcct_entry; 364 pcct_entry = (struct acpi_subtable_header *) 365 ((unsigned long) pcct_entry + pcct_entry->length); 366 367 /* If doorbell is in system memory cache the virt address */ 368 pcct_ss = (struct acpi_pcct_hw_reduced *)pcct_entry; 369 db_reg = &pcct_ss->doorbell_register; 370 if (db_reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) 371 pcc_doorbell_vaddr[i] = acpi_os_ioremap(db_reg->address, 372 db_reg->bit_width/8); 373 } 374 375 pcc_mbox_ctrl.num_chans = count; 376 377 pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans); 378 379 return 0; 380 } 381 382 /** 383 * pcc_mbox_probe - Called when we find a match for the 384 * PCCT platform device. This is purely used to represent 385 * the PCCT as a virtual device for registering with the 386 * generic Mailbox framework. 387 * 388 * @pdev: Pointer to platform device returned when a match 389 * is found. 390 * 391 * Return: 0 for Success, else errno. 392 */ 393 static int pcc_mbox_probe(struct platform_device *pdev) 394 { 395 int ret = 0; 396 397 pcc_mbox_ctrl.chans = pcc_mbox_channels; 398 pcc_mbox_ctrl.ops = &pcc_chan_ops; 399 pcc_mbox_ctrl.dev = &pdev->dev; 400 401 pr_info("Registering PCC driver as Mailbox controller\n"); 402 ret = mbox_controller_register(&pcc_mbox_ctrl); 403 404 if (ret) { 405 pr_err("Err registering PCC as Mailbox controller: %d\n", ret); 406 ret = -ENODEV; 407 } 408 409 return ret; 410 } 411 412 struct platform_driver pcc_mbox_driver = { 413 .probe = pcc_mbox_probe, 414 .driver = { 415 .name = "PCCT", 416 .owner = THIS_MODULE, 417 }, 418 }; 419 420 static int __init pcc_init(void) 421 { 422 int ret; 423 struct platform_device *pcc_pdev; 424 425 if (acpi_disabled) 426 return -ENODEV; 427 428 /* Check if PCC support is available. */ 429 ret = acpi_pcc_probe(); 430 431 if (ret) { 432 pr_debug("ACPI PCC probe failed.\n"); 433 return -ENODEV; 434 } 435 436 pcc_pdev = platform_create_bundle(&pcc_mbox_driver, 437 pcc_mbox_probe, NULL, 0, NULL, 0); 438 439 if (IS_ERR(pcc_pdev)) { 440 pr_debug("Err creating PCC platform bundle\n"); 441 return PTR_ERR(pcc_pdev); 442 } 443 444 return 0; 445 } 446 447 /* 448 * Make PCC init postcore so that users of this mailbox 449 * such as the ACPI Processor driver have it available 450 * at their init. 451 */ 452 postcore_initcall(pcc_init); 453