1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Virtio I2C Bus Driver
5 * The Virtio I2C Specification:
6 * https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex
8 * Copyright (c) 2021 Intel Corporation. All rights reserved.
11 #include <linux/acpi.h>
12 #include <linux/completion.h>
13 #include <linux/err.h>
14 #include <linux/i2c.h>
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/virtio.h>
18 #include <linux/virtio_ids.h>
19 #include <linux/virtio_config.h>
20 #include <linux/virtio_i2c.h>
23 * struct virtio_i2c - virtio I2C data
24 * @vdev: virtio device for this controller
25 * @completion: completion of virtio I2C message
26 * @adap: I2C adapter for this controller
27 * @vq: the virtio virtqueue for communication
30 struct virtio_device *vdev;
31 struct completion completion;
32 struct i2c_adapter adap;
37 * struct virtio_i2c_req - the virtio I2C request structure
38 * @out_hdr: the OUT header of the virtio I2C message
39 * @buf: the buffer into which data is read, or from which it's written
40 * @in_hdr: the IN header of the virtio I2C message
42 struct virtio_i2c_req {
43 struct virtio_i2c_out_hdr out_hdr ____cacheline_aligned;
44 uint8_t *buf ____cacheline_aligned;
45 struct virtio_i2c_in_hdr in_hdr ____cacheline_aligned;
48 static void virtio_i2c_msg_done(struct virtqueue *vq)
50 struct virtio_i2c *vi = vq->vdev->priv;
52 complete(&vi->completion);
55 static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
56 struct virtio_i2c_req *reqs,
57 struct i2c_msg *msgs, int num)
59 struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
62 for (i = 0; i < num; i++) {
63 int outcnt = 0, incnt = 0;
66 * Only 7-bit mode supported for this moment. For the address
67 * format, Please check the Virtio I2C Specification.
69 reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
71 if (msgs[i].flags & I2C_M_RD)
72 reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_M_RD);
75 reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
77 sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
78 sgs[outcnt++] = &out_hdr;
81 reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
85 sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
87 if (msgs[i].flags & I2C_M_RD)
88 sgs[outcnt + incnt++] = &msg_buf;
90 sgs[outcnt++] = &msg_buf;
93 sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
94 sgs[outcnt + incnt++] = &in_hdr;
96 if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) {
97 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false);
105 static int virtio_i2c_complete_reqs(struct virtqueue *vq,
106 struct virtio_i2c_req *reqs,
107 struct i2c_msg *msgs, int num)
109 struct virtio_i2c_req *req;
114 for (i = 0; i < num; i++) {
115 /* Detach the ith request from the vq */
116 req = virtqueue_get_buf(vq, &len);
119 * Condition req == &reqs[i] should always meet since we have
120 * total num requests in the vq. reqs[i] can never be NULL here.
122 if (!failed && (WARN_ON(req != &reqs[i]) ||
123 req->in_hdr.status != VIRTIO_I2C_MSG_OK))
126 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);
135 static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
138 struct virtio_i2c *vi = i2c_get_adapdata(adap);
139 struct virtqueue *vq = vi->vq;
140 struct virtio_i2c_req *reqs;
143 reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
147 count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num);
152 * For the case where count < num, i.e. we weren't able to queue all the
153 * msgs, ideally we should abort right away and return early, but some
154 * of the messages are already sent to the remote I2C controller and the
155 * virtqueue will be left in undefined state in that case. We kick the
156 * remote here to clear the virtqueue, so we can try another set of
160 reinit_completion(&vi->completion);
163 wait_for_completion(&vi->completion);
165 count = virtio_i2c_complete_reqs(vq, reqs, msgs, count);
172 static void virtio_i2c_del_vqs(struct virtio_device *vdev)
174 vdev->config->reset(vdev);
175 vdev->config->del_vqs(vdev);
178 static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
180 struct virtio_device *vdev = vi->vdev;
182 vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg");
183 return PTR_ERR_OR_ZERO(vi->vq);
186 static u32 virtio_i2c_func(struct i2c_adapter *adap)
188 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
191 static struct i2c_algorithm virtio_algorithm = {
192 .master_xfer = virtio_i2c_xfer,
193 .functionality = virtio_i2c_func,
196 static int virtio_i2c_probe(struct virtio_device *vdev)
198 struct virtio_i2c *vi;
201 if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) {
202 dev_err(&vdev->dev, "Zero-length request feature is mandatory\n");
206 vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
213 init_completion(&vi->completion);
215 ret = virtio_i2c_setup_vqs(vi);
219 vi->adap.owner = THIS_MODULE;
220 snprintf(vi->adap.name, sizeof(vi->adap.name),
221 "i2c_virtio at virtio bus %d", vdev->index);
222 vi->adap.algo = &virtio_algorithm;
223 vi->adap.dev.parent = &vdev->dev;
224 vi->adap.dev.of_node = vdev->dev.of_node;
225 i2c_set_adapdata(&vi->adap, vi);
228 * Setup ACPI node for controlled devices which will be probed through
231 ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent));
233 ret = i2c_add_adapter(&vi->adap);
235 virtio_i2c_del_vqs(vdev);
240 static void virtio_i2c_remove(struct virtio_device *vdev)
242 struct virtio_i2c *vi = vdev->priv;
244 i2c_del_adapter(&vi->adap);
245 virtio_i2c_del_vqs(vdev);
248 static struct virtio_device_id id_table[] = {
249 { VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID },
252 MODULE_DEVICE_TABLE(virtio, id_table);
254 #ifdef CONFIG_PM_SLEEP
255 static int virtio_i2c_freeze(struct virtio_device *vdev)
257 virtio_i2c_del_vqs(vdev);
261 static int virtio_i2c_restore(struct virtio_device *vdev)
263 return virtio_i2c_setup_vqs(vdev->priv);
267 static const unsigned int features[] = {
268 VIRTIO_I2C_F_ZERO_LENGTH_REQUEST,
271 static struct virtio_driver virtio_i2c_driver = {
272 .feature_table = features,
273 .feature_table_size = ARRAY_SIZE(features),
274 .id_table = id_table,
275 .probe = virtio_i2c_probe,
276 .remove = virtio_i2c_remove,
278 .name = "i2c_virtio",
280 #ifdef CONFIG_PM_SLEEP
281 .freeze = virtio_i2c_freeze,
282 .restore = virtio_i2c_restore,
285 module_virtio_driver(virtio_i2c_driver);
287 MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>");
288 MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>");
289 MODULE_DESCRIPTION("Virtio i2c bus driver");
290 MODULE_LICENSE("GPL");