[PATCH v3 22/25] bus: mhi: ep: Add support for processing transfer ring

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

Add support for processing the transfer ring from host. For the transfer
ring associated with DL channel, the xfer callback will simply invoked.
For the case of UL channel, the ring elements will be read in a buffer
till the write pointer and later passed to the client driver using the
xfer callback.

The client drivers should provide the callbacks for both UL and DL
channels during registration.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/bus/mhi/ep/main.c | 49 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index b937c6cda9ba..baf383a4857b 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -439,6 +439,55 @@ static int mhi_ep_read_channel(struct mhi_ep_cntrl *mhi_cntrl,
 	return 0;
 }
 
+int mhi_ep_process_tre_ring(struct mhi_ep_ring *ring, struct mhi_ep_ring_element *el)
+{
+	struct mhi_ep_cntrl *mhi_cntrl = ring->mhi_cntrl;
+	struct mhi_result result = {};
+	u32 len = MHI_EP_DEFAULT_MTU;
+	struct mhi_ep_chan *mhi_chan;
+	int ret;
+
+	mhi_chan = &mhi_cntrl->mhi_chan[ring->ch_id];
+
+	/*
+	 * Bail out if transfer callback is not registered for the channel.
+	 * This is most likely due to the client driver not loaded at this point.
+	 */
+	if (!mhi_chan->xfer_cb) {
+		dev_err(&mhi_chan->mhi_dev->dev, "Client driver not available\n");
+		return -ENODEV;
+	}
+
+	if (ring->ch_id % 2) {
+		/* DL channel */
+		result.dir = mhi_chan->dir;
+		mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
+	} else {
+		/* UL channel */
+		do {
+			result.buf_addr = kzalloc(len, GFP_KERNEL);
+			if (!result.buf_addr)
+				return -ENOMEM;
+
+			ret = mhi_ep_read_channel(mhi_cntrl, ring, &result, len);
+			if (ret < 0) {
+				dev_err(&mhi_chan->mhi_dev->dev, "Failed to read channel\n");
+				kfree(result.buf_addr);
+				return ret;
+			}
+
+			result.dir = mhi_chan->dir;
+			mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
+			kfree(result.buf_addr);
+			result.bytes_xferd = 0;
+
+			/* Read until the ring becomes empty */
+		} while (!mhi_ep_queue_is_empty(mhi_chan->mhi_dev, DMA_TO_DEVICE));
+	}
+
+	return 0;
+}
+
 static int mhi_ep_cache_host_cfg(struct mhi_ep_cntrl *mhi_cntrl)
 {
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
-- 
2.25.1