Re: [PATCH v3 20/25] bus: mhi: ep: Add support for processing command ring

Alex Elder
2022-02-15T22:40:11Z

On 2/12/22 12:21 PM, Manivannan Sadhasivam wrote:
> Add support for processing the command ring. Command ring is used by the
> host to issue channel specific commands to the ep device. Following
> commands are supported:
>
> 1. Start channel
> 2. Stop channel
> 3. Reset channel
>
> Once the device receives the command doorbell interrupt from host, it
> executes the command and generates a command completion event to the
> host in the primary event ring.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

I'll let you consider my few comments below, but whether or not you
address them, this looks OK to me.

Reviewed-by: Alex Elder <elder@linaro.org>

> ---
> drivers/bus/mhi/ep/main.c | 151 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 151 insertions(+)
>
> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> index 6378ac5c7e37..4c2ee517832c 100644
> --- a/drivers/bus/mhi/ep/main.c
> +++ b/drivers/bus/mhi/ep/main.c
> @@ -21,6 +21,7 @@
>
> static DEFINE_IDA(mhi_ep_cntrl_ida);
>
> +static int mhi_ep_create_device(struct mhi_ep_cntrl *mhi_cntrl, u32 ch_id);
> static int mhi_ep_destroy_device(struct device *dev, void *data);
>
> static int mhi_ep_send_event(struct mhi_ep_cntrl *mhi_cntrl, u32 ring_idx,
> @@ -185,6 +186,156 @@ void mhi_ep_unmap_free(struct mhi_ep_cntrl *mhi_cntrl, u64 pci_addr, phys_addr_t
> mhi_cntrl->free_addr(mhi_cntrl, phys - offset, virt - offset, size);
> }
>
> +int mhi_ep_process_cmd_ring(struct mhi_ep_ring *ring, struct mhi_ep_ring_element *el)
> +{
> + struct mhi_ep_cntrl *mhi_cntrl = ring->mhi_cntrl;
> + struct device *dev = &mhi_cntrl->mhi_dev->dev;
> + struct mhi_result result = {};
> + struct mhi_ep_chan *mhi_chan;
> + struct mhi_ep_ring *ch_ring;
> + u32 tmp, ch_id;
> + int ret;
> +
> + ch_id = MHI_TRE_GET_CMD_CHID(el);
> + mhi_chan = &mhi_cntrl->mhi_chan[ch_id];
> + ch_ring = &mhi_cntrl->mhi_chan[ch_id].ring;
> +
> + switch (MHI_TRE_GET_CMD_TYPE(el)) {

No MHI_PKT_TYPE_NOOP_CMD?

> + case MHI_PKT_TYPE_START_CHAN_CMD:
> + dev_dbg(dev, "Received START command for channel (%d)\n", ch_id);
> +
> + mutex_lock(&mhi_chan->lock);
> + /* Initialize and configure the corresponding channel ring */
> + if (!ch_ring->started) {
> + ret = mhi_ep_ring_start(mhi_cntrl, ch_ring,
> + (union mhi_ep_ring_ctx *)&mhi_cntrl->ch_ctx_cache[ch_id]);
> + if (ret) {
> + dev_err(dev, "Failed to start ring for channel (%d)\n", ch_id);
> + ret = mhi_ep_send_cmd_comp_event(mhi_cntrl,
> + MHI_EV_CC_UNDEFINED_ERR);
> + if (ret)
> + dev_err(dev, "Error sending completion event (%d)\n",
> + MHI_EV_CC_UNDEFINED_ERR);

Print the value of ret in the above message (not UNDEFINED_ERR).

> +
> + goto err_unlock;
> + }
> + }
> +
> + /* Enable DB for the channel */
> + mhi_ep_mmio_enable_chdb_a7(mhi_cntrl, ch_id);

If an error occurs later, this will be enabled. Is that what
you want? Maybe wait to enable the doorbell until everything
else succeeds.

> +
> + /* Set channel state to RUNNING */
> + mhi_chan->state = MHI_CH_STATE_RUNNING;
> + tmp = le32_to_cpu(mhi_cntrl->ch_ctx_cache[ch_id].chcfg);
> + tmp &= ~CHAN_CTX_CHSTATE_MASK;
> + tmp |= FIELD_PREP(CHAN_CTX_CHSTATE_MASK, MHI_CH_STATE_RUNNING);
> + mhi_cntrl->ch_ctx_cache[ch_id].chcfg = cpu_to_le32(tmp);
> +
> + ret = mhi_ep_send_cmd_comp_event(mhi_cntrl, MHI_EV_CC_SUCCESS);
> + if (ret) {
> + dev_err(dev, "Error sending command completion event (%d)\n",
> + MHI_EV_CC_SUCCESS);
> + goto err_unlock;
> + }
> +
> + mutex_unlock(&mhi_chan->lock);
> +
> + /*
> + * Create MHI device only during UL channel start. Since the MHI
> + * channels operate in a pair, we'll associate both UL and DL
> + * channels to the same device.
> + *
> + * We also need to check for mhi_dev != NULL because, the host
> + * will issue START_CHAN command during resume and we don't
> + * destroy the device during suspend.
> + */
> + if (!(ch_id % 2) && !mhi_chan->mhi_dev) {
> + ret = mhi_ep_create_device(mhi_cntrl, ch_id);
> + if (ret) {

If this occurs, the host will already have been told the
request completed successfully. Is that a problem that
can/should be avoided?

> + dev_err(dev, "Error creating device for channel (%d)\n", ch_id);
> + return ret;
> + }
> + }
> +
> + break;
> + case MHI_PKT_TYPE_STOP_CHAN_CMD:
> + dev_dbg(dev, "Received STOP command for channel (%d)\n", ch_id);
> + if (!ch_ring->started) {
> + dev_err(dev, "Channel (%d) not opened\n", ch_id);
> + return -ENODEV;
> + }
> +
> + mutex_lock(&mhi_chan->lock);
> + /* Disable DB for the channel */
> + mhi_ep_mmio_disable_chdb_a7(mhi_cntrl, ch_id);
> +
> + /* Send channel disconnect status to client drivers */
> + result.transaction_status = -ENOTCONN;
> + result.bytes_xferd = 0;
> + mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
> +
> + /* Set channel state to STOP */
> + mhi_chan->state = MHI_CH_STATE_STOP;
> + tmp = le32_to_cpu(mhi_cntrl->ch_ctx_cache[ch_id].chcfg);
> + tmp &= ~CHAN_CTX_CHSTATE_MASK;
> + tmp |= FIELD_PREP(CHAN_CTX_CHSTATE_MASK, MHI_CH_STATE_STOP);
> + mhi_cntrl->ch_ctx_cache[ch_id].chcfg = cpu_to_le32(tmp);
> +
> + ret = mhi_ep_send_cmd_comp_event(mhi_cntrl, MHI_EV_CC_SUCCESS);
> + if (ret) {
> + dev_err(dev, "Error sending command completion event (%d)\n",
> + MHI_EV_CC_SUCCESS);
> + goto err_unlock;
> + }
> +
> + mutex_unlock(&mhi_chan->lock);
> + break;
> + case MHI_PKT_TYPE_RESET_CHAN_CMD:
> + dev_dbg(dev, "Received STOP command for channel (%d)\n", ch_id);
> + if (!ch_ring->started) {
> + dev_err(dev, "Channel (%d) not opened\n", ch_id);
> + return -ENODEV;
> + }
> +
> + mutex_lock(&mhi_chan->lock);
> + /* Stop and reset the transfer ring */
> + mhi_ep_ring_reset(mhi_cntrl, ch_ring);
> +
> + /* Send channel disconnect status to client driver */
> + result.transaction_status = -ENOTCONN;
> + result.bytes_xferd = 0;
> + mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
> +
> + /* Set channel state to DISABLED */
> + mhi_chan->state = MHI_CH_STATE_DISABLED;
> + tmp = le32_to_cpu(mhi_cntrl->ch_ctx_cache[ch_id].chcfg);
> + tmp &= ~CHAN_CTX_CHSTATE_MASK;
> + tmp |= FIELD_PREP(CHAN_CTX_CHSTATE_MASK, MHI_CH_STATE_DISABLED);
> + mhi_cntrl->ch_ctx_cache[ch_id].chcfg = cpu_to_le32(tmp);
> +
> + ret = mhi_ep_send_cmd_comp_event(mhi_cntrl, MHI_EV_CC_SUCCESS);
> + if (ret) {
> + dev_err(dev, "Error sending command completion event (%d)\n",
> + MHI_EV_CC_SUCCESS);
> + goto err_unlock;
> + }
> +
> + mutex_unlock(&mhi_chan->lock);
> + break;
> + default:
> + dev_err(dev, "Invalid command received: %d for channel (%d)\n",
> + MHI_TRE_GET_CMD_TYPE(el), ch_id);
> + return -EINVAL;
> + }
> +
> + return 0;
> +
> +err_unlock:
> + mutex_unlock(&mhi_chan->lock);
> +
> + return ret;
> +}
> +
> static int mhi_ep_cache_host_cfg(struct mhi_ep_cntrl *mhi_cntrl)
> {
> struct device *dev = &mhi_cntrl->mhi_dev->dev;