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)))
 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(&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(&msgs[i], 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, outcnt, incnt, &reqs[i], GFP_KERNEL)) {
101			i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], 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		wait_for_completion(&req->completion);
120
121		if (!failed && req->in_hdr.status != VIRTIO_I2C_MSG_OK)
122			failed = true;
123
124		i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);
125
126		if (!failed)
127			j++;
128	}
129
130	return j;
131}
132
133static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
134			   int num)
135{
136	struct virtio_i2c *vi = i2c_get_adapdata(adap);
137	struct virtqueue *vq = vi->vq;
138	struct virtio_i2c_req *reqs;
139	int count;
140
141	reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
142	if (!reqs)
143		return -ENOMEM;
144
145	count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num);
146	if (!count)
147		goto err_free;
148
149	/*
150	 * For the case where count < num, i.e. we weren't able to queue all the
151	 * msgs, ideally we should abort right away and return early, but some
152	 * of the messages are already sent to the remote I2C controller and the
153	 * virtqueue will be left in undefined state in that case. We kick the
154	 * remote here to clear the virtqueue, so we can try another set of
155	 * messages later on.
156	 */
157	virtqueue_kick(vq);
158
159	count = virtio_i2c_complete_reqs(vq, reqs, msgs, count);
160
161err_free:
162	kfree(reqs);
163	return count;
164}
165
166static void virtio_i2c_del_vqs(struct virtio_device *vdev)
167{
168	virtio_reset_device(vdev);
169	vdev->config->del_vqs(vdev);
170}
171
172static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
173{
174	struct virtio_device *vdev = vi->vdev;
175
176	vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg");
177	return PTR_ERR_OR_ZERO(vi->vq);
178}
179
180static u32 virtio_i2c_func(struct i2c_adapter *adap)
181{
182	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
183}
184
185static struct i2c_algorithm virtio_algorithm = {
186	.master_xfer = virtio_i2c_xfer,
187	.functionality = virtio_i2c_func,
188};
189
190static int virtio_i2c_probe(struct virtio_device *vdev)
191{
192	struct virtio_i2c *vi;
193	int ret;
194
195	if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) {
196		dev_err(&vdev->dev, "Zero-length request feature is mandatory\n");
197		return -EINVAL;
198	}
199
200	vi = devm_kzalloc(&vdev->dev, 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(vi->adap.name, sizeof(vi->adap.name),
213		 "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(&vi->adap, 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(&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(&vi->adap);
237	virtio_i2c_del_vqs(vdev);
238}
239
240static 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(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");