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SubjectRe: [PATCH v4 25/27] bus: mhi: ep: Add support for queueing SKBs to the host
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On 2/28/22 6:43 AM, Manivannan Sadhasivam wrote:
> Add support for queueing SKBs to the host over the transfer ring of the
> relevant channel. The mhi_ep_queue_skb() API will be used by the client
> networking drivers to queue the SKBs to the host over MHI bus.
>
> The host will add ring elements to the transfer ring periodically for
> the device and the device will write SKBs to the ring elements. If a
> single SKB doesn't fit in a ring element (TRE), it will be placed in
> multiple ring elements and the overflow event will be sent for all ring
> elements except the last one. For the last ring element, the EOT event
> will be sent indicating the packet boundary.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Looks good.

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

> ---
> drivers/bus/mhi/ep/main.c | 82 +++++++++++++++++++++++++++++++++++++++
> include/linux/mhi_ep.h | 9 +++++
> 2 files changed, 91 insertions(+)
>
> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> index 63e14d55aa06..25d34cf26fd7 100644
> --- a/drivers/bus/mhi/ep/main.c
> +++ b/drivers/bus/mhi/ep/main.c
> @@ -471,6 +471,88 @@ int mhi_ep_process_ch_ring(struct mhi_ep_ring *ring, struct mhi_ring_element *el
> return 0;
> }
>
> +/* TODO: Handle partially formed TDs */
> +int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb)
> +{
> + struct mhi_ep_cntrl *mhi_cntrl = mhi_dev->mhi_cntrl;
> + struct mhi_ep_chan *mhi_chan = mhi_dev->dl_chan;
> + struct device *dev = &mhi_chan->mhi_dev->dev;
> + struct mhi_ring_element *el;
> + u32 buf_left, read_offset;
> + struct mhi_ep_ring *ring;
> + enum mhi_ev_ccs code;
> + void *read_addr;
> + u64 write_addr;
> + size_t tr_len;
> + u32 tre_len;
> + int ret;
> +
> + buf_left = skb->len;
> + ring = &mhi_cntrl->mhi_chan[mhi_chan->chan].ring;
> +
> + mutex_lock(&mhi_chan->lock);
> +
> + do {
> + /* Don't process the transfer ring if the channel is not in RUNNING state */
> + if (mhi_chan->state != MHI_CH_STATE_RUNNING) {
> + dev_err(dev, "Channel not available\n");
> + ret = -ENODEV;
> + goto err_exit;
> + }
> +
> + if (mhi_ep_queue_is_empty(mhi_dev, DMA_FROM_DEVICE)) {
> + dev_err(dev, "TRE not available!\n");
> + ret = -ENOSPC;
> + goto err_exit;
> + }
> +
> + el = &ring->ring_cache[ring->rd_offset];
> + tre_len = MHI_TRE_DATA_GET_LEN(el);
> +
> + tr_len = min(buf_left, tre_len);
> + read_offset = skb->len - buf_left;
> + read_addr = skb->data + read_offset;
> + write_addr = MHI_TRE_DATA_GET_PTR(el);
> +
> + dev_dbg(dev, "Writing %zd bytes to channel (%u)\n", tr_len, ring->ch_id);
> + ret = mhi_cntrl->write_to_host(mhi_cntrl, read_addr, write_addr, tr_len);
> + if (ret < 0) {
> + dev_err(dev, "Error writing to the channel\n");
> + goto err_exit;
> + }
> +
> + buf_left -= tr_len;
> + /*
> + * For all TREs queued by the host for DL channel, only the EOT flag will be set.
> + * If the packet doesn't fit into a single TRE, send the OVERFLOW event to
> + * the host so that the host can adjust the packet boundary to next TREs. Else send
> + * the EOT event to the host indicating the packet boundary.
> + */
> + if (buf_left)
> + code = MHI_EV_CC_OVERFLOW;
> + else
> + code = MHI_EV_CC_EOT;
> +
> + ret = mhi_ep_send_completion_event(mhi_cntrl, ring, el, tr_len, code);
> + if (ret) {
> + dev_err(dev, "Error sending transfer completion event\n");
> + goto err_exit;
> + }
> +
> + mhi_ep_ring_inc_index(ring);
> + } while (buf_left);
> +
> + mutex_unlock(&mhi_chan->lock);
> +
> + return 0;
> +
> +err_exit:
> + mutex_unlock(&mhi_chan->lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(mhi_ep_queue_skb);
> +
> static int mhi_ep_cache_host_cfg(struct mhi_ep_cntrl *mhi_cntrl)
> {
> size_t cmd_ctx_host_size, ch_ctx_host_size, ev_ctx_host_size;
> diff --git a/include/linux/mhi_ep.h b/include/linux/mhi_ep.h
> index 74170dad09f6..bd3ffde01f04 100644
> --- a/include/linux/mhi_ep.h
> +++ b/include/linux/mhi_ep.h
> @@ -272,4 +272,13 @@ void mhi_ep_power_down(struct mhi_ep_cntrl *mhi_cntrl);
> */
> bool mhi_ep_queue_is_empty(struct mhi_ep_device *mhi_dev, enum dma_data_direction dir);
>
> +/**
> + * mhi_ep_queue_skb - Send SKBs to host over MHI Endpoint
> + * @mhi_dev: Device associated with the DL channel
> + * @skb: SKBs to be queued
> + *
> + * Return: 0 if the SKBs has been sent successfully, a negative error code otherwise.
> + */
> +int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb);
> +
> #endif

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