blob: f10a603b13fb02157f33ef237d3dc00737aac0dc [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Virtio I2C Bus Driver
*
* The Virtio I2C Specification:
* https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex
*
* Copyright (c) 2021 Intel Corporation. All rights reserved.
*/
#include <linux/acpi.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/virtio.h>
#include <linux/virtio_ids.h>
#include <linux/virtio_config.h>
#include <linux/virtio_i2c.h>
/**
* struct virtio_i2c - virtio I2C data
* @vdev: virtio device for this controller
* @completion: completion of virtio I2C message
* @adap: I2C adapter for this controller
* @vq: the virtio virtqueue for communication
*/
struct virtio_i2c {
struct virtio_device *vdev;
struct completion completion;
struct i2c_adapter adap;
struct virtqueue *vq;
};
/**
* struct virtio_i2c_req - the virtio I2C request structure
* @out_hdr: the OUT header of the virtio I2C message
* @buf: the buffer into which data is read, or from which it's written
* @in_hdr: the IN header of the virtio I2C message
*/
struct virtio_i2c_req {
struct virtio_i2c_out_hdr out_hdr ____cacheline_aligned;
uint8_t *buf ____cacheline_aligned;
struct virtio_i2c_in_hdr in_hdr ____cacheline_aligned;
};
static void virtio_i2c_msg_done(struct virtqueue *vq)
{
struct virtio_i2c *vi = vq->vdev->priv;
complete(&vi->completion);
}
static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
struct virtio_i2c_req *reqs,
struct i2c_msg *msgs, int num)
{
struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
int i;
for (i = 0; i < num; i++) {
int outcnt = 0, incnt = 0;
/*
* We don't support 0 length messages and so filter out
* 0 length transfers by using i2c_adapter_quirks.
*/
if (!msgs[i].len)
break;
/*
* Only 7-bit mode supported for this moment. For the address
* format, Please check the Virtio I2C Specification.
*/
reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
if (i != num - 1)
reqs[i].out_hdr.flags = cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
sgs[outcnt++] = &out_hdr;
reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
if (!reqs[i].buf)
break;
sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
if (msgs[i].flags & I2C_M_RD)
sgs[outcnt + incnt++] = &msg_buf;
else
sgs[outcnt++] = &msg_buf;
sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
sgs[outcnt + incnt++] = &in_hdr;
if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) {
i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false);
break;
}
}
return i;
}
static int virtio_i2c_complete_reqs(struct virtqueue *vq,
struct virtio_i2c_req *reqs,
struct i2c_msg *msgs, int num,
bool timedout)
{
struct virtio_i2c_req *req;
bool failed = timedout;
unsigned int len;
int i, j = 0;
for (i = 0; i < num; i++) {
/* Detach the ith request from the vq */
req = virtqueue_get_buf(vq, &len);
/*
* Condition req == &reqs[i] should always meet since we have
* total num requests in the vq. reqs[i] can never be NULL here.
*/
if (!failed && (WARN_ON(req != &reqs[i]) ||
req->in_hdr.status != VIRTIO_I2C_MSG_OK))
failed = true;
i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);
if (!failed)
j++;
}
return timedout ? -ETIMEDOUT : j;
}
static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int num)
{
struct virtio_i2c *vi = i2c_get_adapdata(adap);
struct virtqueue *vq = vi->vq;
struct virtio_i2c_req *reqs;
unsigned long time_left;
int count;
reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
if (!reqs)
return -ENOMEM;
count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num);
if (!count)
goto err_free;
/*
* For the case where count < num, i.e. we weren't able to queue all the
* msgs, ideally we should abort right away and return early, but some
* of the messages are already sent to the remote I2C controller and the
* virtqueue will be left in undefined state in that case. We kick the
* remote here to clear the virtqueue, so we can try another set of
* messages later on.
*/
reinit_completion(&vi->completion);
virtqueue_kick(vq);
time_left = wait_for_completion_timeout(&vi->completion, adap->timeout);
if (!time_left)
dev_err(&adap->dev, "virtio i2c backend timeout.\n");
count = virtio_i2c_complete_reqs(vq, reqs, msgs, count, !time_left);
err_free:
kfree(reqs);
return count;
}
static void virtio_i2c_del_vqs(struct virtio_device *vdev)
{
vdev->config->reset(vdev);
vdev->config->del_vqs(vdev);
}
static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
{
struct virtio_device *vdev = vi->vdev;
vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg");
return PTR_ERR_OR_ZERO(vi->vq);
}
static u32 virtio_i2c_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
}
static struct i2c_algorithm virtio_algorithm = {
.master_xfer = virtio_i2c_xfer,
.functionality = virtio_i2c_func,
};
static const struct i2c_adapter_quirks virtio_i2c_quirks = {
.flags = I2C_AQ_NO_ZERO_LEN,
};
static int virtio_i2c_probe(struct virtio_device *vdev)
{
struct virtio_i2c *vi;
int ret;
vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
if (!vi)
return -ENOMEM;
vdev->priv = vi;
vi->vdev = vdev;
init_completion(&vi->completion);
ret = virtio_i2c_setup_vqs(vi);
if (ret)
return ret;
vi->adap.owner = THIS_MODULE;
snprintf(vi->adap.name, sizeof(vi->adap.name),
"i2c_virtio at virtio bus %d", vdev->index);
vi->adap.algo = &virtio_algorithm;
vi->adap.quirks = &virtio_i2c_quirks;
vi->adap.dev.parent = &vdev->dev;
vi->adap.dev.of_node = vdev->dev.of_node;
i2c_set_adapdata(&vi->adap, vi);
/*
* Setup ACPI node for controlled devices which will be probed through
* ACPI.
*/
ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent));
ret = i2c_add_adapter(&vi->adap);
if (ret)
virtio_i2c_del_vqs(vdev);
return ret;
}
static void virtio_i2c_remove(struct virtio_device *vdev)
{
struct virtio_i2c *vi = vdev->priv;
i2c_del_adapter(&vi->adap);
virtio_i2c_del_vqs(vdev);
}
static struct virtio_device_id id_table[] = {
{ VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID },
{}
};
MODULE_DEVICE_TABLE(virtio, id_table);
#ifdef CONFIG_PM_SLEEP
static int virtio_i2c_freeze(struct virtio_device *vdev)
{
virtio_i2c_del_vqs(vdev);
return 0;
}
static int virtio_i2c_restore(struct virtio_device *vdev)
{
return virtio_i2c_setup_vqs(vdev->priv);
}
#endif
static struct virtio_driver virtio_i2c_driver = {
.id_table = id_table,
.probe = virtio_i2c_probe,
.remove = virtio_i2c_remove,
.driver = {
.name = "i2c_virtio",
},
#ifdef CONFIG_PM_SLEEP
.freeze = virtio_i2c_freeze,
.restore = virtio_i2c_restore,
#endif
};
module_virtio_driver(virtio_i2c_driver);
MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>");
MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>");
MODULE_DESCRIPTION("Virtio i2c bus driver");
MODULE_LICENSE("GPL");