283 lines
6.7 KiB
C
283 lines
6.7 KiB
C
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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Virtio I2C Bus Driver
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*
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* The Virtio I2C Specification:
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* https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex
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*
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* Copyright (c) 2021 Intel Corporation. All rights reserved.
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*/
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#include <linux/acpi.h>
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#include <linux/completion.h>
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#include <linux/err.h>
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#include <linux/i2c.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/virtio.h>
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#include <linux/virtio_ids.h>
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#include <linux/virtio_config.h>
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#include <linux/virtio_i2c.h>
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/**
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* struct virtio_i2c - virtio I2C data
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* @vdev: virtio device for this controller
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* @adap: I2C adapter for this controller
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* @vq: the virtio virtqueue for communication
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*/
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struct virtio_i2c {
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struct virtio_device *vdev;
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struct i2c_adapter adap;
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struct virtqueue *vq;
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};
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/**
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* struct virtio_i2c_req - the virtio I2C request structure
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* @completion: completion of virtio I2C message
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* @out_hdr: the OUT header of the virtio I2C message
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* @buf: the buffer into which data is read, or from which it's written
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* @in_hdr: the IN header of the virtio I2C message
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*/
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struct virtio_i2c_req {
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struct completion completion;
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struct virtio_i2c_out_hdr out_hdr ____cacheline_aligned;
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uint8_t *buf ____cacheline_aligned;
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struct virtio_i2c_in_hdr in_hdr ____cacheline_aligned;
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};
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static void virtio_i2c_msg_done(struct virtqueue *vq)
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{
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struct virtio_i2c_req *req;
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unsigned int len;
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while ((req = virtqueue_get_buf(vq, &len)))
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complete(&req->completion);
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}
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static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
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struct virtio_i2c_req *reqs,
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struct i2c_msg *msgs, int num)
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{
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struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
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int i;
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for (i = 0; i < num; i++) {
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int outcnt = 0, incnt = 0;
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init_completion(&reqs[i].completion);
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/*
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* Only 7-bit mode supported for this moment. For the address
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* format, Please check the Virtio I2C Specification.
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*/
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reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
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if (msgs[i].flags & I2C_M_RD)
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reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_M_RD);
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if (i != num - 1)
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reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
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sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
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sgs[outcnt++] = &out_hdr;
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if (msgs[i].len) {
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reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
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if (!reqs[i].buf)
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break;
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sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
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if (msgs[i].flags & I2C_M_RD)
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sgs[outcnt + incnt++] = &msg_buf;
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else
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sgs[outcnt++] = &msg_buf;
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}
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sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
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sgs[outcnt + incnt++] = &in_hdr;
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if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) {
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i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false);
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break;
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}
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}
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return i;
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}
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static int virtio_i2c_complete_reqs(struct virtqueue *vq,
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struct virtio_i2c_req *reqs,
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struct i2c_msg *msgs, int num)
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{
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bool failed = false;
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int i, j = 0;
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for (i = 0; i < num; i++) {
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struct virtio_i2c_req *req = &reqs[i];
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wait_for_completion(&req->completion);
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if (!failed && req->in_hdr.status != VIRTIO_I2C_MSG_OK)
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failed = true;
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i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed);
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if (!failed)
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j++;
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}
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return j;
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}
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static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
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int num)
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{
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struct virtio_i2c *vi = i2c_get_adapdata(adap);
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struct virtqueue *vq = vi->vq;
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struct virtio_i2c_req *reqs;
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int count;
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reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
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if (!reqs)
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return -ENOMEM;
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count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num);
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if (!count)
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goto err_free;
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/*
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* For the case where count < num, i.e. we weren't able to queue all the
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* msgs, ideally we should abort right away and return early, but some
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* of the messages are already sent to the remote I2C controller and the
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* virtqueue will be left in undefined state in that case. We kick the
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* remote here to clear the virtqueue, so we can try another set of
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* messages later on.
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*/
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virtqueue_kick(vq);
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count = virtio_i2c_complete_reqs(vq, reqs, msgs, count);
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err_free:
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kfree(reqs);
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return count;
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}
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static void virtio_i2c_del_vqs(struct virtio_device *vdev)
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{
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virtio_reset_device(vdev);
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vdev->config->del_vqs(vdev);
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}
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static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
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{
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struct virtio_device *vdev = vi->vdev;
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vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg");
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return PTR_ERR_OR_ZERO(vi->vq);
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}
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static u32 virtio_i2c_func(struct i2c_adapter *adap)
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{
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return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
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}
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static struct i2c_algorithm virtio_algorithm = {
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.master_xfer = virtio_i2c_xfer,
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.functionality = virtio_i2c_func,
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};
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static int virtio_i2c_probe(struct virtio_device *vdev)
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{
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struct virtio_i2c *vi;
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int ret;
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if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) {
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dev_err(&vdev->dev, "Zero-length request feature is mandatory\n");
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return -EINVAL;
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}
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vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
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if (!vi)
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return -ENOMEM;
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vdev->priv = vi;
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vi->vdev = vdev;
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ret = virtio_i2c_setup_vqs(vi);
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if (ret)
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return ret;
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vi->adap.owner = THIS_MODULE;
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snprintf(vi->adap.name, sizeof(vi->adap.name),
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"i2c_virtio at virtio bus %d", vdev->index);
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vi->adap.algo = &virtio_algorithm;
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vi->adap.dev.parent = &vdev->dev;
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vi->adap.dev.of_node = vdev->dev.of_node;
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i2c_set_adapdata(&vi->adap, vi);
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/*
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* Setup ACPI node for controlled devices which will be probed through
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* ACPI.
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*/
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ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent));
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ret = i2c_add_adapter(&vi->adap);
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if (ret)
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virtio_i2c_del_vqs(vdev);
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return ret;
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}
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static void virtio_i2c_remove(struct virtio_device *vdev)
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{
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struct virtio_i2c *vi = vdev->priv;
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i2c_del_adapter(&vi->adap);
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virtio_i2c_del_vqs(vdev);
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}
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static struct virtio_device_id id_table[] = {
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{ VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID },
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{}
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};
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MODULE_DEVICE_TABLE(virtio, id_table);
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#ifdef CONFIG_PM_SLEEP
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static int virtio_i2c_freeze(struct virtio_device *vdev)
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{
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virtio_i2c_del_vqs(vdev);
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return 0;
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}
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static int virtio_i2c_restore(struct virtio_device *vdev)
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{
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return virtio_i2c_setup_vqs(vdev->priv);
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}
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#endif
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static const unsigned int features[] = {
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VIRTIO_I2C_F_ZERO_LENGTH_REQUEST,
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};
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static struct virtio_driver virtio_i2c_driver = {
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.feature_table = features,
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.feature_table_size = ARRAY_SIZE(features),
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.id_table = id_table,
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.probe = virtio_i2c_probe,
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.remove = virtio_i2c_remove,
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.driver = {
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.name = "i2c_virtio",
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},
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#ifdef CONFIG_PM_SLEEP
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.freeze = virtio_i2c_freeze,
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.restore = virtio_i2c_restore,
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#endif
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};
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module_virtio_driver(virtio_i2c_driver);
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MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>");
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MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>");
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MODULE_DESCRIPTION("Virtio i2c bus driver");
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MODULE_LICENSE("GPL");
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