279 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Virtio I2C Bus Driver4 *5 * The Virtio I2C Specification:6 * https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex7 *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 data24 * @vdev: virtio device for this controller25 * @adap: I2C adapter for this controller26 * @vq: the virtio virtqueue for communication27 */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 structure36 * @completion: completion of virtio I2C message37 * @out_hdr: the OUT header of the virtio I2C message38 * @buf: the buffer into which data is read, or from which it's written39 * @in_hdr: the IN header of the virtio I2C message40 */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 address71 * 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 else94 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 the151 * msgs, ideally we should abort right away and return early, but some152 * of the messages are already sent to the remote I2C controller and the153 * virtqueue will be left in undefined state in that case. We kick the154 * remote here to clear the virtqueue, so we can try another set of155 * 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 const struct i2c_algorithm virtio_algorithm = {186 .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 through221 * 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 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(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