1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Virtio I2C Bus Driver
4 *
5 * The Virtio I2C Specification:
6 * https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex
7 *
8 * Copyright (c) 2021 Intel Corporation. All rights reserved.
9 */
10
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>
21
22/**
23 * struct virtio_i2c - virtio I2C data
24 * @vdev: virtio device for this controller
25 * @adap: I2C adapter for this controller
26 * @vq: the virtio virtqueue for communication
27 */
28struct virtio_i2c {
29 struct virtio_device *vdev;
30 struct i2c_adapter adap;
31 struct virtqueue *vq;
32};
33
34/**
35 * struct virtio_i2c_req - the virtio I2C request structure
36 * @completion: completion of virtio I2C message
37 * @out_hdr: the OUT header of the virtio I2C message
38 * @buf: the buffer into which data is read, or from which it's written
39 * @in_hdr: the IN header of the virtio I2C message
40 */
41struct virtio_i2c_req {
42 struct completion completion;
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;
46};
47
48static void virtio_i2c_msg_done(struct virtqueue *vq)
49{
50 struct virtio_i2c_req *req;
51 unsigned int len;
52
53 while ((req = virtqueue_get_buf(vq, len: &len)))
54 complete(&req->completion);
55}
56
57static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
58 struct virtio_i2c_req *reqs,
59 struct i2c_msg *msgs, int num)
60{
61 struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
62 int i;
63
64 for (i = 0; i < num; i++) {
65 int outcnt = 0, incnt = 0;
66
67 init_completion(x: &reqs[i].completion);
68
69 /*
70 * Only 7-bit mode supported for this moment. For the address
71 * format, Please check the Virtio I2C Specification.
72 */
73 reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
74
75 if (msgs[i].flags & I2C_M_RD)
76 reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_M_RD);
77
78 if (i != num - 1)
79 reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
80
81 sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
82 sgs[outcnt++] = &out_hdr;
83
84 if (msgs[i].len) {
85 reqs[i].buf = i2c_get_dma_safe_msg_buf(msg: &msgs[i], threshold: 1);
86 if (!reqs[i].buf)
87 break;
88
89 sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
90
91 if (msgs[i].flags & I2C_M_RD)
92 sgs[outcnt + incnt++] = &msg_buf;
93 else
94 sgs[outcnt++] = &msg_buf;
95 }
96
97 sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
98 sgs[outcnt + incnt++] = &in_hdr;
99
100 if (virtqueue_add_sgs(vq, sgs, out_sgs: outcnt, in_sgs: incnt, data: &reqs[i], GFP_KERNEL)) {
101 i2c_put_dma_safe_msg_buf(buf: reqs[i].buf, msg: &msgs[i], xferred: false);
102 break;
103 }
104 }
105
106 return i;
107}
108
109static int virtio_i2c_complete_reqs(struct virtqueue *vq,
110 struct virtio_i2c_req *reqs,
111 struct i2c_msg *msgs, int num)
112{
113 bool failed = false;
114 int i, j = 0;
115
116 for (i = 0; i < num; i++) {
117 struct virtio_i2c_req *req = &reqs[i];
118
119 if (!failed) {
120 if (wait_for_completion_interruptible(x: &req->completion))
121 failed = true;
122 else if (req->in_hdr.status != VIRTIO_I2C_MSG_OK)
123 failed = true;
124 else
125 j++;
126 }
127
128 i2c_put_dma_safe_msg_buf(buf: reqs[i].buf, msg: &msgs[i], xferred: !failed);
129 }
130
131 return j;
132}
133
134static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
135 int num)
136{
137 struct virtio_i2c *vi = i2c_get_adapdata(adap);
138 struct virtqueue *vq = vi->vq;
139 struct virtio_i2c_req *reqs;
140 int count;
141
142 reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
143 if (!reqs)
144 return -ENOMEM;
145
146 count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num);
147 if (!count)
148 goto err_free;
149
150 /*
151 * For the case where count < num, i.e. we weren't able to queue all the
152 * msgs, ideally we should abort right away and return early, but some
153 * of the messages are already sent to the remote I2C controller and the
154 * virtqueue will be left in undefined state in that case. We kick the
155 * remote here to clear the virtqueue, so we can try another set of
156 * messages later on.
157 */
158 virtqueue_kick(vq);
159
160 count = virtio_i2c_complete_reqs(vq, reqs, msgs, num: count);
161
162err_free:
163 kfree(objp: reqs);
164 return count;
165}
166
167static void virtio_i2c_del_vqs(struct virtio_device *vdev)
168{
169 virtio_reset_device(dev: vdev);
170 vdev->config->del_vqs(vdev);
171}
172
173static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
174{
175 struct virtio_device *vdev = vi->vdev;
176
177 vi->vq = virtio_find_single_vq(vdev, c: virtio_i2c_msg_done, n: "msg");
178 return PTR_ERR_OR_ZERO(ptr: vi->vq);
179}
180
181static u32 virtio_i2c_func(struct i2c_adapter *adap)
182{
183 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
184}
185
186static const struct i2c_algorithm virtio_algorithm = {
187 .xfer = virtio_i2c_xfer,
188 .functionality = virtio_i2c_func,
189};
190
191static int virtio_i2c_probe(struct virtio_device *vdev)
192{
193 struct virtio_i2c *vi;
194 int ret;
195
196 if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST))
197 return dev_err_probe(dev: &vdev->dev, err: -EINVAL,
198 fmt: "Zero-length request feature is mandatory\n");
199
200 vi = devm_kzalloc(dev: &vdev->dev, size: sizeof(*vi), GFP_KERNEL);
201 if (!vi)
202 return -ENOMEM;
203
204 vdev->priv = vi;
205 vi->vdev = vdev;
206
207 ret = virtio_i2c_setup_vqs(vi);
208 if (ret)
209 return ret;
210
211 vi->adap.owner = THIS_MODULE;
212 snprintf(buf: vi->adap.name, size: sizeof(vi->adap.name),
213 fmt: "i2c_virtio at virtio bus %d", vdev->index);
214 vi->adap.algo = &virtio_algorithm;
215 vi->adap.dev.parent = &vdev->dev;
216 vi->adap.dev.of_node = vdev->dev.of_node;
217 i2c_set_adapdata(adap: &vi->adap, data: vi);
218
219 /*
220 * Setup ACPI node for controlled devices which will be probed through
221 * ACPI.
222 */
223 ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent));
224
225 ret = i2c_add_adapter(adap: &vi->adap);
226 if (ret)
227 virtio_i2c_del_vqs(vdev);
228
229 return ret;
230}
231
232static void virtio_i2c_remove(struct virtio_device *vdev)
233{
234 struct virtio_i2c *vi = vdev->priv;
235
236 i2c_del_adapter(adap: &vi->adap);
237 virtio_i2c_del_vqs(vdev);
238}
239
240static const struct virtio_device_id id_table[] = {
241 { VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID },
242 {}
243};
244MODULE_DEVICE_TABLE(virtio, id_table);
245
246static int virtio_i2c_freeze(struct virtio_device *vdev)
247{
248 virtio_i2c_del_vqs(vdev);
249 return 0;
250}
251
252static int virtio_i2c_restore(struct virtio_device *vdev)
253{
254 return virtio_i2c_setup_vqs(vi: vdev->priv);
255}
256
257static const unsigned int features[] = {
258 VIRTIO_I2C_F_ZERO_LENGTH_REQUEST,
259};
260
261static struct virtio_driver virtio_i2c_driver = {
262 .feature_table = features,
263 .feature_table_size = ARRAY_SIZE(features),
264 .id_table = id_table,
265 .probe = virtio_i2c_probe,
266 .remove = virtio_i2c_remove,
267 .driver = {
268 .name = "i2c_virtio",
269 },
270 .freeze = pm_sleep_ptr(virtio_i2c_freeze),
271 .restore = pm_sleep_ptr(virtio_i2c_restore),
272};
273module_virtio_driver(virtio_i2c_driver);
274
275MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>");
276MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>");
277MODULE_DESCRIPTION("Virtio i2c bus driver");
278MODULE_LICENSE("GPL");
279

source code of linux/drivers/i2c/busses/i2c-virtio.c