drivers/i2c/busses/i2c-virtio.c

   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  */
  28 struct 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  */
  41 struct 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
  48 static 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
  57 static 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
 109 static 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
 133 static 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
 161 err_free:
 162         kfree(reqs);
 163         return count;
 164 }
 165
 166 static void virtio_i2c_del_vqs(struct virtio_device *vdev)
 167 {
 168         virtio_reset_device(vdev);
 169         vdev->config->del_vqs(vdev);
 170 }
 171
 172 static 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
 180 static u32 virtio_i2c_func(struct i2c_adapter *adap)
 181 {
 182         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 183 }
 184
 185 static const struct i2c_algorithm virtio_algorithm = {
 186         .xfer = virtio_i2c_xfer,
 187         .functionality = virtio_i2c_func,
 188 };
 189
 190 static 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
 232 static 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
 240 static const struct virtio_device_id id_table[] = {
 241         { VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID },
 242         {}
 243 };
 244 MODULE_DEVICE_TABLE(virtio, id_table);
 245
 246 static int virtio_i2c_freeze(struct virtio_device *vdev)
 247 {
 248         virtio_i2c_del_vqs(vdev);
 249         return 0;
 250 }
 251
 252 static int virtio_i2c_restore(struct virtio_device *vdev)
 253 {
 254         return virtio_i2c_setup_vqs(vdev->priv);
 255 }
 256
 257 static const unsigned int features[] = {
 258         VIRTIO_I2C_F_ZERO_LENGTH_REQUEST,
 259 };
 260
 261 static 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 };
 273 module_virtio_driver(virtio_i2c_driver);
 274
 275 MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>");
 276 MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>");
 277 MODULE_DESCRIPTION("Virtio i2c bus driver");
 278 MODULE_LICENSE("GPL");