drivers/i2c/busses/i2c-designware-amdpsp.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/i2c.h>
   4 #include <linux/pci.h>
   5 #include <linux/psp-platform-access.h>
   6 #include <linux/psp.h>
   7 #include <linux/workqueue.h>
   8
   9 #include "i2c-designware-core.h"
  10
  11 #define PSP_I2C_RESERVATION_TIME_MS 100
  12
  13 #define PSP_I2C_REQ_RETRY_CNT           400
  14 #define PSP_I2C_REQ_RETRY_DELAY_US      (25 * USEC_PER_MSEC)
  15 #define PSP_I2C_REQ_STS_OK              0x0
  16 #define PSP_I2C_REQ_STS_BUS_BUSY        0x1
  17 #define PSP_I2C_REQ_STS_INV_PARAM       0x3
  18
  19 enum psp_i2c_req_type {
  20         PSP_I2C_REQ_ACQUIRE,
  21         PSP_I2C_REQ_RELEASE,
  22         PSP_I2C_REQ_MAX
  23 };
  24
  25 struct psp_i2c_req {
  26         struct psp_req_buffer_hdr hdr;
  27         enum psp_i2c_req_type type;
  28 };
  29
  30 static DEFINE_MUTEX(psp_i2c_access_mutex);
  31 static unsigned long psp_i2c_sem_acquired;
  32 static u32 psp_i2c_access_count;
  33 static bool psp_i2c_mbox_fail;
  34 static struct device *psp_i2c_dev;
  35
  36 static int (*_psp_send_i2c_req)(struct psp_i2c_req *req);
  37
  38 /* Helper to verify status returned by PSP */
  39 static int check_i2c_req_sts(struct psp_i2c_req *req)
  40 {
  41         u32 status;
  42
  43         /* Status field in command-response buffer is updated by PSP */
  44         status = READ_ONCE(req->hdr.status);
  45
  46         switch (status) {
  47         case PSP_I2C_REQ_STS_OK:
  48                 return 0;
  49         case PSP_I2C_REQ_STS_BUS_BUSY:
  50                 return -EBUSY;
  51         case PSP_I2C_REQ_STS_INV_PARAM:
  52         default:
  53                 return -EIO;
  54         }
  55 }
  56
  57 /*
  58  * Errors in x86-PSP i2c-arbitration protocol may occur at two levels:
  59  * 1. mailbox communication - PSP is not operational or some IO errors with
  60  *    basic communication had happened.
  61  * 2. i2c-requests - PSP refuses to grant i2c arbitration to x86 for too long.
  62  *
  63  * In order to distinguish between these in error handling code all mailbox
  64  * communication errors on the first level (from CCP symbols) will be passed
  65  * up and if -EIO is returned the second level will be checked.
  66  */
  67 static int psp_send_i2c_req_cezanne(struct psp_i2c_req *req)
  68 {
  69         int ret;
  70
  71         ret = psp_send_platform_access_msg(PSP_I2C_REQ_BUS_CMD, (struct psp_request *)req);
  72         if (ret == -EIO)
  73                 return check_i2c_req_sts(req);
  74
  75         return ret;
  76 }
  77
  78 static int psp_send_i2c_req_doorbell(struct psp_i2c_req *req)
  79 {
  80         int ret;
  81
  82         ret = psp_ring_platform_doorbell(req->type, &req->hdr.status);
  83         if (ret == -EIO)
  84                 return check_i2c_req_sts(req);
  85
  86         return ret;
  87 }
  88
  89 static int psp_send_i2c_req(enum psp_i2c_req_type i2c_req_type)
  90 {
  91         struct psp_i2c_req *req;
  92         unsigned long start;
  93         int status, ret;
  94
  95         /* Allocate command-response buffer */
  96         req = kzalloc(sizeof(*req), GFP_KERNEL);
  97         if (!req)
  98                 return -ENOMEM;
  99
 100         req->hdr.payload_size = sizeof(*req);
 101         req->type = i2c_req_type;
 102
 103         start = jiffies;
 104         ret = read_poll_timeout(_psp_send_i2c_req, status,
 105                                 (status != -EBUSY),
 106                                 PSP_I2C_REQ_RETRY_DELAY_US,
 107                                 PSP_I2C_REQ_RETRY_CNT * PSP_I2C_REQ_RETRY_DELAY_US,
 108                                 0, req);
 109         if (ret) {
 110                 dev_err(psp_i2c_dev, "Timed out waiting for PSP to %s I2C bus\n",
 111                         (i2c_req_type == PSP_I2C_REQ_ACQUIRE) ?
 112                         "release" : "acquire");
 113                 goto cleanup;
 114         }
 115
 116         ret = status;
 117         if (ret) {
 118                 dev_err(psp_i2c_dev, "PSP communication error\n");
 119                 goto cleanup;
 120         }
 121
 122         dev_dbg(psp_i2c_dev, "Request accepted by PSP after %ums\n",
 123                 jiffies_to_msecs(jiffies - start));
 124
 125 cleanup:
 126         if (ret) {
 127                 dev_err(psp_i2c_dev, "Assume i2c bus is for exclusive host usage\n");
 128                 psp_i2c_mbox_fail = true;
 129         }
 130
 131         kfree(req);
 132         return ret;
 133 }
 134
 135 static void release_bus(void)
 136 {
 137         int status;
 138
 139         if (!psp_i2c_sem_acquired)
 140                 return;
 141
 142         status = psp_send_i2c_req(PSP_I2C_REQ_RELEASE);
 143         if (status)
 144                 return;
 145
 146         dev_dbg(psp_i2c_dev, "PSP semaphore held for %ums\n",
 147                 jiffies_to_msecs(jiffies - psp_i2c_sem_acquired));
 148
 149         psp_i2c_sem_acquired = 0;
 150 }
 151
 152 static void psp_release_i2c_bus_deferred(struct work_struct *work)
 153 {
 154         mutex_lock(&psp_i2c_access_mutex);
 155
 156         /*
 157          * If there is any pending transaction, cannot release the bus here.
 158          * psp_release_i2c_bus will take care of this later.
 159          */
 160         if (psp_i2c_access_count)
 161                 goto cleanup;
 162
 163         release_bus();
 164
 165 cleanup:
 166         mutex_unlock(&psp_i2c_access_mutex);
 167 }
 168 static DECLARE_DELAYED_WORK(release_queue, psp_release_i2c_bus_deferred);
 169
 170 static int psp_acquire_i2c_bus(void)
 171 {
 172         int status;
 173
 174         mutex_lock(&psp_i2c_access_mutex);
 175
 176         /* Return early if mailbox malfunctioned */
 177         if (psp_i2c_mbox_fail)
 178                 goto cleanup;
 179
 180         psp_i2c_access_count++;
 181
 182         /*
 183          * No need to request bus arbitration once we are inside semaphore
 184          * reservation period.
 185          */
 186         if (psp_i2c_sem_acquired)
 187                 goto cleanup;
 188
 189         status = psp_send_i2c_req(PSP_I2C_REQ_ACQUIRE);
 190         if (status)
 191                 goto cleanup;
 192
 193         psp_i2c_sem_acquired = jiffies;
 194
 195         schedule_delayed_work(&release_queue,
 196                               msecs_to_jiffies(PSP_I2C_RESERVATION_TIME_MS));
 197
 198         /*
 199          * In case of errors with PSP arbitrator psp_i2c_mbox_fail variable is
 200          * set above. As a consequence consecutive calls to acquire will bypass
 201          * communication with PSP. At any case i2c bus is granted to the caller,
 202          * thus always return success.
 203          */
 204 cleanup:
 205         mutex_unlock(&psp_i2c_access_mutex);
 206         return 0;
 207 }
 208
 209 static void psp_release_i2c_bus(void)
 210 {
 211         mutex_lock(&psp_i2c_access_mutex);
 212
 213         /* Return early if mailbox was malfunctional */
 214         if (psp_i2c_mbox_fail)
 215                 goto cleanup;
 216
 217         /*
 218          * If we are last owner of PSP semaphore, need to release aribtration
 219          * via mailbox.
 220          */
 221         psp_i2c_access_count--;
 222         if (psp_i2c_access_count)
 223                 goto cleanup;
 224
 225         /*
 226          * Send a release command to PSP if the semaphore reservation timeout
 227          * elapsed but x86 still owns the controller.
 228          */
 229         if (!delayed_work_pending(&release_queue))
 230                 release_bus();
 231
 232 cleanup:
 233         mutex_unlock(&psp_i2c_access_mutex);
 234 }
 235
 236 /*
 237  * Locking methods are based on the default implementation from
 238  * drivers/i2c/i2c-core-base.c, but with psp acquire and release operations
 239  * added. With this in place we can ensure that i2c clients on the bus shared
 240  * with psp are able to lock HW access to the bus for arbitrary number of
 241  * operations - that is e.g. write-wait-read.
 242  */
 243 static void i2c_adapter_dw_psp_lock_bus(struct i2c_adapter *adapter,
 244                                         unsigned int flags)
 245 {
 246         psp_acquire_i2c_bus();
 247         rt_mutex_lock_nested(&adapter->bus_lock, i2c_adapter_depth(adapter));
 248 }
 249
 250 static int i2c_adapter_dw_psp_trylock_bus(struct i2c_adapter *adapter,
 251                                           unsigned int flags)
 252 {
 253         int ret;
 254
 255         ret = rt_mutex_trylock(&adapter->bus_lock);
 256         if (ret)
 257                 return ret;
 258
 259         psp_acquire_i2c_bus();
 260
 261         return ret;
 262 }
 263
 264 static void i2c_adapter_dw_psp_unlock_bus(struct i2c_adapter *adapter,
 265                                           unsigned int flags)
 266 {
 267         psp_release_i2c_bus();
 268         rt_mutex_unlock(&adapter->bus_lock);
 269 }
 270
 271 static const struct i2c_lock_operations i2c_dw_psp_lock_ops = {
 272         .lock_bus = i2c_adapter_dw_psp_lock_bus,
 273         .trylock_bus = i2c_adapter_dw_psp_trylock_bus,
 274         .unlock_bus = i2c_adapter_dw_psp_unlock_bus,
 275 };
 276
 277 int i2c_dw_amdpsp_probe_lock_support(struct dw_i2c_dev *dev)
 278 {
 279         struct pci_dev *rdev;
 280
 281         if (!IS_REACHABLE(CONFIG_CRYPTO_DEV_CCP_DD))
 282                 return -ENODEV;
 283
 284         if (!dev)
 285                 return -ENODEV;
 286
 287         if (!(dev->flags & ARBITRATION_SEMAPHORE))
 288                 return -ENODEV;
 289
 290         /* Allow to bind only one instance of a driver */
 291         if (psp_i2c_dev)
 292                 return -EEXIST;
 293
 294         /* Cezanne uses platform mailbox, Mendocino and later use doorbell */
 295         rdev = pci_get_domain_bus_and_slot(0, 0, PCI_DEVFN(0, 0));
 296         if (rdev->device == 0x1630)
 297                 _psp_send_i2c_req = psp_send_i2c_req_cezanne;
 298         else
 299                 _psp_send_i2c_req = psp_send_i2c_req_doorbell;
 300         pci_dev_put(rdev);
 301
 302         if (psp_check_platform_access_status())
 303                 return -EPROBE_DEFER;
 304
 305         psp_i2c_dev = dev->dev;
 306
 307         dev_info(psp_i2c_dev, "I2C bus managed by AMD PSP\n");
 308
 309         /*
 310          * Install global locking callbacks for adapter as well as internal i2c
 311          * controller locks.
 312          */
 313         dev->adapter.lock_ops = &i2c_dw_psp_lock_ops;
 314         dev->acquire_lock = psp_acquire_i2c_bus;
 315         dev->release_lock = psp_release_i2c_bus;
 316
 317         return 0;
 318 }