LXR linux/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 * @completion: completion of virtio I2C message
  26 * @adap: I2C adapter for this controller
  27 * @vq: the virtio virtqueue for communication
  28 */
  29struct virtio_i2c {
  30        struct virtio_device *vdev;
  31        struct completion completion;
  32        struct i2c_adapter adap;
  33        struct virtqueue *vq;
  34};
  35
  36/**
  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
  41 */
  42struct 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;
  46};
  47
  48static void virtio_i2c_msg_done(struct virtqueue *vq)
  49{
  50        struct virtio_i2c *vi = vq->vdev->priv;
  51
  52        complete(&vi->completion);
  53}
  54
  55static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
  56                                   struct virtio_i2c_req *reqs,
  57                                   struct i2c_msg *msgs, int num)
  58{
  59        struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
  60        int i;
  61
  62        for (i = 0; i < num; i++) {
  63                int outcnt = 0, incnt = 0;
  64
  65                /*
  66                 * We don't support 0 length messages and so filter out
  67                 * 0 length transfers by using i2c_adapter_quirks.
  68                 */
  69                if (!msgs[i].len)
  70                        break;
  71
  72                /*
  73                 * Only 7-bit mode supported for this moment. For the address
  74                 * format, Please check the Virtio I2C Specification.
  75                 */
  76                reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
  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                reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
  85                if (!reqs[i].buf)
  86                        break;
  87
  88                sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
  89
  90                if (msgs[i].flags & I2C_M_RD)
  91                        sgs[outcnt + incnt++] = &msg_buf;
  92                else
  93                        sgs[outcnt++] = &msg_buf;
  94
  95                sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
  96                sgs[outcnt + incnt++] = &in_hdr;
  97
  98                if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) {
  99                        i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false);
 100                        break;
 101                }
 102        }
 103
 104        return i;
 105}
 106
 107static int virtio_i2c_complete_reqs(struct virtqueue *vq,
 108                                    struct virtio_i2c_req *reqs,
 109                                    struct i2c_msg *msgs, int num,
 110                                    bool timedout)
 111{
 112        struct virtio_i2c_req *req;
 113        bool failed = timedout;
 114        unsigned int len;
 115        int i, j = 0;
 116
 117        for (i = 0; i < num; i++) {
 118                /* Detach the ith request from the vq */
 119                req = virtqueue_get_buf(vq, &len);
 120
 121                /*
 122                 * Condition req == &reqs[i] should always meet since we have
 123                 * total num requests in the vq. reqs[i] can never be NULL here.
 124                 */
 125                if (!failed && (WARN_ON(req != &reqs[i]) ||
 126                                req->in_hdr.status != VIRTIO_I2C_MSG_OK))
 127                        failed = true;
 128
 129                i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);
 130
 131                if (!failed)
 132                        j++;
 133        }
 134
 135        return timedout ? -ETIMEDOUT : j;
 136}
 137
 138static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 139                           int num)
 140{
 141        struct virtio_i2c *vi = i2c_get_adapdata(adap);
 142        struct virtqueue *vq = vi->vq;
 143        struct virtio_i2c_req *reqs;
 144        unsigned long time_left;
 145        int count;
 146
 147        reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
 148        if (!reqs)
 149                return -ENOMEM;
 150
 151        count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num);
 152        if (!count)
 153                goto err_free;
 154
 155        /*
 156         * For the case where count < num, i.e. we weren't able to queue all the
 157         * msgs, ideally we should abort right away and return early, but some
 158         * of the messages are already sent to the remote I2C controller and the
 159         * virtqueue will be left in undefined state in that case. We kick the
 160         * remote here to clear the virtqueue, so we can try another set of
 161         * messages later on.
 162         */
 163
 164        reinit_completion(&vi->completion);
 165        virtqueue_kick(vq);
 166
 167        time_left = wait_for_completion_timeout(&vi->completion, adap->timeout);
 168        if (!time_left)
 169                dev_err(&adap->dev, "virtio i2c backend timeout.\n");
 170
 171        count = virtio_i2c_complete_reqs(vq, reqs, msgs, count, !time_left);
 172
 173err_free:
 174        kfree(reqs);
 175        return count;
 176}
 177
 178static void virtio_i2c_del_vqs(struct virtio_device *vdev)
 179{
 180        vdev->config->reset(vdev);
 181        vdev->config->del_vqs(vdev);
 182}
 183
 184static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
 185{
 186        struct virtio_device *vdev = vi->vdev;
 187
 188        vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg");
 189        return PTR_ERR_OR_ZERO(vi->vq);
 190}
 191
 192static u32 virtio_i2c_func(struct i2c_adapter *adap)
 193{
 194        return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
 195}
 196
 197static struct i2c_algorithm virtio_algorithm = {
 198        .master_xfer = virtio_i2c_xfer,
 199        .functionality = virtio_i2c_func,
 200};
 201
 202static const struct i2c_adapter_quirks virtio_i2c_quirks = {
 203        .flags = I2C_AQ_NO_ZERO_LEN,
 204};
 205
 206static int virtio_i2c_probe(struct virtio_device *vdev)
 207{
 208        struct virtio_i2c *vi;
 209        int ret;
 210
 211        vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
 212        if (!vi)
 213                return -ENOMEM;
 214
 215        vdev->priv = vi;
 216        vi->vdev = vdev;
 217
 218        init_completion(&vi->completion);
 219
 220        ret = virtio_i2c_setup_vqs(vi);
 221        if (ret)
 222                return ret;
 223
 224        vi->adap.owner = THIS_MODULE;
 225        snprintf(vi->adap.name, sizeof(vi->adap.name),
 226                 "i2c_virtio at virtio bus %d", vdev->index);
 227        vi->adap.algo = &virtio_algorithm;
 228        vi->adap.quirks = &virtio_i2c_quirks;
 229        vi->adap.dev.parent = &vdev->dev;
 230        vi->adap.dev.of_node = vdev->dev.of_node;
 231        i2c_set_adapdata(&vi->adap, vi);
 232
 233        /*
 234         * Setup ACPI node for controlled devices which will be probed through
 235         * ACPI.
 236         */
 237        ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent));
 238
 239        ret = i2c_add_adapter(&vi->adap);
 240        if (ret)
 241                virtio_i2c_del_vqs(vdev);
 242
 243        return ret;
 244}
 245
 246static void virtio_i2c_remove(struct virtio_device *vdev)
 247{
 248        struct virtio_i2c *vi = vdev->priv;
 249
 250        i2c_del_adapter(&vi->adap);
 251        virtio_i2c_del_vqs(vdev);
 252}
 253
 254static struct virtio_device_id id_table[] = {
 255        { VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID },
 256        {}
 257};
 258MODULE_DEVICE_TABLE(virtio, id_table);
 259
 260#ifdef CONFIG_PM_SLEEP
 261static int virtio_i2c_freeze(struct virtio_device *vdev)
 262{
 263        virtio_i2c_del_vqs(vdev);
 264        return 0;
 265}
 266
 267static int virtio_i2c_restore(struct virtio_device *vdev)
 268{
 269        return virtio_i2c_setup_vqs(vdev->priv);
 270}
 271#endif
 272
 273static struct virtio_driver virtio_i2c_driver = {
 274        .id_table       = id_table,
 275        .probe          = virtio_i2c_probe,
 276        .remove         = virtio_i2c_remove,
 277        .driver = {
 278                .name   = "i2c_virtio",
 279        },
 280#ifdef CONFIG_PM_SLEEP
 281        .freeze = virtio_i2c_freeze,
 282        .restore = virtio_i2c_restore,
 283#endif
 284};
 285module_virtio_driver(virtio_i2c_driver);
 286
 287MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>");
 288MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>");
 289MODULE_DESCRIPTION("Virtio i2c bus driver");
 290MODULE_LICENSE("GPL");
 291