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3a29355a VK |
1 | // SPDX-License-Identifier: GPL-2.0+ |
2 | /* | |
3 | * GPIO driver for virtio-based virtual GPIO controllers | |
4 | * | |
5 | * Copyright (C) 2021 metux IT consult | |
6 | * Enrico Weigelt, metux IT consult <info@metux.net> | |
7 | * | |
8 | * Copyright (C) 2021 Linaro. | |
9 | * Viresh Kumar <viresh.kumar@linaro.org> | |
10 | */ | |
11 | ||
12 | #include <linux/completion.h> | |
13 | #include <linux/err.h> | |
14 | #include <linux/gpio/driver.h> | |
15 | #include <linux/io.h> | |
16 | #include <linux/kernel.h> | |
17 | #include <linux/module.h> | |
18 | #include <linux/mutex.h> | |
19 | #include <linux/virtio_config.h> | |
20 | #include <uapi/linux/virtio_gpio.h> | |
21 | #include <uapi/linux/virtio_ids.h> | |
22 | ||
23 | struct virtio_gpio_line { | |
24 | struct mutex lock; /* Protects line operation */ | |
25 | struct completion completion; | |
26 | struct virtio_gpio_request req ____cacheline_aligned; | |
27 | struct virtio_gpio_response res ____cacheline_aligned; | |
28 | unsigned int rxlen; | |
29 | }; | |
30 | ||
31 | struct virtio_gpio { | |
32 | struct virtio_device *vdev; | |
33 | struct mutex lock; /* Protects virtqueue operation */ | |
34 | struct gpio_chip gc; | |
35 | struct virtio_gpio_config config; | |
36 | struct virtio_gpio_line *lines; | |
37 | struct virtqueue *request_vq; | |
38 | }; | |
39 | ||
40 | static int _virtio_gpio_req(struct virtio_gpio *vgpio, u16 type, u16 gpio, | |
41 | u8 txvalue, u8 *rxvalue, void *response, u32 rxlen) | |
42 | { | |
43 | struct virtio_gpio_line *line = &vgpio->lines[gpio]; | |
44 | struct virtio_gpio_request *req = &line->req; | |
45 | struct virtio_gpio_response *res = response; | |
46 | struct scatterlist *sgs[2], req_sg, res_sg; | |
47 | struct device *dev = &vgpio->vdev->dev; | |
48 | int ret; | |
49 | ||
50 | /* | |
51 | * Prevent concurrent requests for the same line since we have | |
52 | * pre-allocated request/response buffers for each GPIO line. Moreover | |
53 | * Linux always accesses a GPIO line sequentially, so this locking shall | |
54 | * always go through without any delays. | |
55 | */ | |
56 | mutex_lock(&line->lock); | |
57 | ||
58 | req->type = cpu_to_le16(type); | |
59 | req->gpio = cpu_to_le16(gpio); | |
60 | req->value = txvalue; | |
61 | ||
62 | sg_init_one(&req_sg, req, sizeof(*req)); | |
63 | sg_init_one(&res_sg, res, rxlen); | |
64 | sgs[0] = &req_sg; | |
65 | sgs[1] = &res_sg; | |
66 | ||
67 | line->rxlen = 0; | |
68 | reinit_completion(&line->completion); | |
69 | ||
70 | /* | |
71 | * Virtqueue callers need to ensure they don't call its APIs with other | |
72 | * virtqueue operations at the same time. | |
73 | */ | |
74 | mutex_lock(&vgpio->lock); | |
75 | ret = virtqueue_add_sgs(vgpio->request_vq, sgs, 1, 1, line, GFP_KERNEL); | |
76 | if (ret) { | |
77 | dev_err(dev, "failed to add request to vq\n"); | |
78 | mutex_unlock(&vgpio->lock); | |
79 | goto out; | |
80 | } | |
81 | ||
82 | virtqueue_kick(vgpio->request_vq); | |
83 | mutex_unlock(&vgpio->lock); | |
84 | ||
85 | if (!wait_for_completion_timeout(&line->completion, HZ)) { | |
86 | dev_err(dev, "GPIO operation timed out\n"); | |
87 | ret = -ETIMEDOUT; | |
88 | goto out; | |
89 | } | |
90 | ||
91 | if (unlikely(res->status != VIRTIO_GPIO_STATUS_OK)) { | |
92 | dev_err(dev, "GPIO request failed: %d\n", gpio); | |
93 | ret = -EINVAL; | |
94 | goto out; | |
95 | } | |
96 | ||
97 | if (unlikely(line->rxlen != rxlen)) { | |
98 | dev_err(dev, "GPIO operation returned incorrect len (%u : %u)\n", | |
99 | rxlen, line->rxlen); | |
100 | ret = -EINVAL; | |
101 | goto out; | |
102 | } | |
103 | ||
104 | if (rxvalue) | |
105 | *rxvalue = res->value; | |
106 | ||
107 | out: | |
108 | mutex_unlock(&line->lock); | |
109 | return ret; | |
110 | } | |
111 | ||
112 | static int virtio_gpio_req(struct virtio_gpio *vgpio, u16 type, u16 gpio, | |
113 | u8 txvalue, u8 *rxvalue) | |
114 | { | |
115 | struct virtio_gpio_line *line = &vgpio->lines[gpio]; | |
116 | struct virtio_gpio_response *res = &line->res; | |
117 | ||
118 | return _virtio_gpio_req(vgpio, type, gpio, txvalue, rxvalue, res, | |
119 | sizeof(*res)); | |
120 | } | |
121 | ||
122 | static void virtio_gpio_free(struct gpio_chip *gc, unsigned int gpio) | |
123 | { | |
124 | struct virtio_gpio *vgpio = gpiochip_get_data(gc); | |
125 | ||
126 | virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio, | |
127 | VIRTIO_GPIO_DIRECTION_NONE, NULL); | |
128 | } | |
129 | ||
130 | static int virtio_gpio_get_direction(struct gpio_chip *gc, unsigned int gpio) | |
131 | { | |
132 | struct virtio_gpio *vgpio = gpiochip_get_data(gc); | |
133 | u8 direction; | |
134 | int ret; | |
135 | ||
136 | ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_DIRECTION, gpio, 0, | |
137 | &direction); | |
138 | if (ret) | |
139 | return ret; | |
140 | ||
141 | switch (direction) { | |
142 | case VIRTIO_GPIO_DIRECTION_IN: | |
143 | return GPIO_LINE_DIRECTION_IN; | |
144 | case VIRTIO_GPIO_DIRECTION_OUT: | |
145 | return GPIO_LINE_DIRECTION_OUT; | |
146 | default: | |
147 | return -EINVAL; | |
148 | } | |
149 | } | |
150 | ||
151 | static int virtio_gpio_direction_input(struct gpio_chip *gc, unsigned int gpio) | |
152 | { | |
153 | struct virtio_gpio *vgpio = gpiochip_get_data(gc); | |
154 | ||
155 | return virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio, | |
156 | VIRTIO_GPIO_DIRECTION_IN, NULL); | |
157 | } | |
158 | ||
159 | static int virtio_gpio_direction_output(struct gpio_chip *gc, unsigned int gpio, | |
160 | int value) | |
161 | { | |
162 | struct virtio_gpio *vgpio = gpiochip_get_data(gc); | |
163 | int ret; | |
164 | ||
165 | ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_VALUE, gpio, value, NULL); | |
166 | if (ret) | |
167 | return ret; | |
168 | ||
169 | return virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio, | |
170 | VIRTIO_GPIO_DIRECTION_OUT, NULL); | |
171 | } | |
172 | ||
173 | static int virtio_gpio_get(struct gpio_chip *gc, unsigned int gpio) | |
174 | { | |
175 | struct virtio_gpio *vgpio = gpiochip_get_data(gc); | |
176 | u8 value; | |
177 | int ret; | |
178 | ||
179 | ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_VALUE, gpio, 0, &value); | |
180 | return ret ? ret : value; | |
181 | } | |
182 | ||
183 | static void virtio_gpio_set(struct gpio_chip *gc, unsigned int gpio, int value) | |
184 | { | |
185 | struct virtio_gpio *vgpio = gpiochip_get_data(gc); | |
186 | ||
187 | virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_VALUE, gpio, value, NULL); | |
188 | } | |
189 | ||
190 | static void virtio_gpio_request_vq(struct virtqueue *vq) | |
191 | { | |
192 | struct virtio_gpio_line *line; | |
193 | unsigned int len; | |
194 | ||
195 | do { | |
196 | line = virtqueue_get_buf(vq, &len); | |
197 | if (!line) | |
198 | return; | |
199 | ||
200 | line->rxlen = len; | |
201 | complete(&line->completion); | |
202 | } while (1); | |
203 | } | |
204 | ||
205 | static void virtio_gpio_free_vqs(struct virtio_device *vdev) | |
206 | { | |
207 | vdev->config->reset(vdev); | |
208 | vdev->config->del_vqs(vdev); | |
209 | } | |
210 | ||
211 | static int virtio_gpio_alloc_vqs(struct virtio_gpio *vgpio, | |
212 | struct virtio_device *vdev) | |
213 | { | |
214 | const char * const names[] = { "requestq" }; | |
215 | vq_callback_t *cbs[] = { | |
216 | virtio_gpio_request_vq, | |
217 | }; | |
218 | struct virtqueue *vqs[1] = { NULL }; | |
219 | int ret; | |
220 | ||
221 | ret = virtio_find_vqs(vdev, 1, vqs, cbs, names, NULL); | |
222 | if (ret) { | |
223 | dev_err(&vdev->dev, "failed to find vqs: %d\n", ret); | |
224 | return ret; | |
225 | } | |
226 | ||
227 | if (!vqs[0]) { | |
228 | dev_err(&vdev->dev, "failed to find requestq vq\n"); | |
229 | return -ENODEV; | |
230 | } | |
231 | vgpio->request_vq = vqs[0]; | |
232 | ||
233 | return 0; | |
234 | } | |
235 | ||
236 | static const char **virtio_gpio_get_names(struct virtio_gpio *vgpio) | |
237 | { | |
238 | struct virtio_gpio_config *config = &vgpio->config; | |
239 | struct virtio_gpio_response_get_names *res; | |
240 | struct device *dev = &vgpio->vdev->dev; | |
241 | u8 *gpio_names, *str; | |
242 | const char **names; | |
243 | int i, ret, len; | |
244 | ||
245 | if (!config->gpio_names_size) | |
246 | return NULL; | |
247 | ||
248 | len = sizeof(*res) + config->gpio_names_size; | |
249 | res = devm_kzalloc(dev, len, GFP_KERNEL); | |
250 | if (!res) | |
251 | return NULL; | |
252 | gpio_names = res->value; | |
253 | ||
254 | ret = _virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_NAMES, 0, 0, NULL, | |
255 | res, len); | |
256 | if (ret) { | |
257 | dev_err(dev, "Failed to get GPIO names: %d\n", ret); | |
258 | return NULL; | |
259 | } | |
260 | ||
261 | names = devm_kcalloc(dev, config->ngpio, sizeof(*names), GFP_KERNEL); | |
262 | if (!names) | |
263 | return NULL; | |
264 | ||
265 | /* NULL terminate the string instead of checking it */ | |
266 | gpio_names[config->gpio_names_size - 1] = '\0'; | |
267 | ||
268 | for (i = 0, str = gpio_names; i < config->ngpio; i++) { | |
269 | names[i] = str; | |
270 | str += strlen(str) + 1; /* zero-length strings are allowed */ | |
271 | ||
272 | if (str > gpio_names + config->gpio_names_size) { | |
273 | dev_err(dev, "gpio_names block is too short (%d)\n", i); | |
274 | return NULL; | |
275 | } | |
276 | } | |
277 | ||
278 | return names; | |
279 | } | |
280 | ||
281 | static int virtio_gpio_probe(struct virtio_device *vdev) | |
282 | { | |
283 | struct virtio_gpio_config *config; | |
284 | struct device *dev = &vdev->dev; | |
285 | struct virtio_gpio *vgpio; | |
286 | int ret, i; | |
287 | ||
288 | vgpio = devm_kzalloc(dev, sizeof(*vgpio), GFP_KERNEL); | |
289 | if (!vgpio) | |
290 | return -ENOMEM; | |
291 | ||
292 | config = &vgpio->config; | |
293 | ||
294 | /* Read configuration */ | |
295 | virtio_cread_bytes(vdev, 0, config, sizeof(*config)); | |
296 | config->gpio_names_size = le32_to_cpu(config->gpio_names_size); | |
297 | config->ngpio = le16_to_cpu(config->ngpio); | |
298 | if (!config->ngpio) { | |
299 | dev_err(dev, "Number of GPIOs can't be zero\n"); | |
300 | return -EINVAL; | |
301 | } | |
302 | ||
303 | vgpio->lines = devm_kcalloc(dev, config->ngpio, sizeof(*vgpio->lines), GFP_KERNEL); | |
304 | if (!vgpio->lines) | |
305 | return -ENOMEM; | |
306 | ||
307 | for (i = 0; i < config->ngpio; i++) { | |
308 | mutex_init(&vgpio->lines[i].lock); | |
309 | init_completion(&vgpio->lines[i].completion); | |
310 | } | |
311 | ||
312 | mutex_init(&vgpio->lock); | |
313 | vdev->priv = vgpio; | |
314 | ||
315 | vgpio->vdev = vdev; | |
316 | vgpio->gc.free = virtio_gpio_free; | |
317 | vgpio->gc.get_direction = virtio_gpio_get_direction; | |
318 | vgpio->gc.direction_input = virtio_gpio_direction_input; | |
319 | vgpio->gc.direction_output = virtio_gpio_direction_output; | |
320 | vgpio->gc.get = virtio_gpio_get; | |
321 | vgpio->gc.set = virtio_gpio_set; | |
322 | vgpio->gc.ngpio = config->ngpio; | |
323 | vgpio->gc.base = -1; /* Allocate base dynamically */ | |
324 | vgpio->gc.label = dev_name(dev); | |
325 | vgpio->gc.parent = dev; | |
326 | vgpio->gc.owner = THIS_MODULE; | |
327 | vgpio->gc.can_sleep = true; | |
328 | ||
329 | ret = virtio_gpio_alloc_vqs(vgpio, vdev); | |
330 | if (ret) | |
331 | return ret; | |
332 | ||
333 | /* Mark the device ready to perform operations from within probe() */ | |
334 | virtio_device_ready(vdev); | |
335 | ||
336 | vgpio->gc.names = virtio_gpio_get_names(vgpio); | |
337 | ||
338 | ret = gpiochip_add_data(&vgpio->gc, vgpio); | |
339 | if (ret) { | |
340 | virtio_gpio_free_vqs(vdev); | |
341 | dev_err(dev, "Failed to add virtio-gpio controller\n"); | |
342 | } | |
343 | ||
344 | return ret; | |
345 | } | |
346 | ||
347 | static void virtio_gpio_remove(struct virtio_device *vdev) | |
348 | { | |
349 | struct virtio_gpio *vgpio = vdev->priv; | |
350 | ||
351 | gpiochip_remove(&vgpio->gc); | |
352 | virtio_gpio_free_vqs(vdev); | |
353 | } | |
354 | ||
355 | static const struct virtio_device_id id_table[] = { | |
356 | { VIRTIO_ID_GPIO, VIRTIO_DEV_ANY_ID }, | |
357 | {}, | |
358 | }; | |
359 | MODULE_DEVICE_TABLE(virtio, id_table); | |
360 | ||
361 | static struct virtio_driver virtio_gpio_driver = { | |
362 | .id_table = id_table, | |
363 | .probe = virtio_gpio_probe, | |
364 | .remove = virtio_gpio_remove, | |
365 | .driver = { | |
366 | .name = KBUILD_MODNAME, | |
367 | .owner = THIS_MODULE, | |
368 | }, | |
369 | }; | |
370 | module_virtio_driver(virtio_gpio_driver); | |
371 | ||
372 | MODULE_AUTHOR("Enrico Weigelt, metux IT consult <info@metux.net>"); | |
373 | MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.org>"); | |
374 | MODULE_DESCRIPTION("VirtIO GPIO driver"); | |
375 | MODULE_LICENSE("GPL"); |