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, req: (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(msg: req->type, result: &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(size: 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(objp: 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(i2c_req_type: 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(lock: &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(i2c_req_type: PSP_I2C_REQ_ACQUIRE); |
190 | if (status) |
191 | goto cleanup; |
192 | |
193 | psp_i2c_sem_acquired = jiffies; |
194 | |
195 | schedule_delayed_work(dwork: &release_queue, |
196 | delay: 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(lock: &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(lock: &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(lock: &adapter->bus_lock, subclass: 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(lock: &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(lock: &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(domain: 0, bus: 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(dev: 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 | } |
319 | |