[PATCH v2 5/5] bus: mhi: ep: Use batched read for ring caching

[Sumit Kumar]

Optimise ring caching in __mhi_ep_cache_ring().
For the non-wraparound case, use read_sync(); for the wraparound case
where ring data spans two non-contiguous host memory regions, both the
tail portion (start -> ring_size) and head portion (0 -> end) are
submitted using the new read_batch() API in a single operation.
On DMA-capable platforms this transfers both segments in one DMA
transaction.

Signed-off-by: Sumit Kumar <sumit.kumar@xxxxxxxxxxxxxxxx>
---
 drivers/bus/mhi/ep/ring.c | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/drivers/bus/mhi/ep/ring.c b/drivers/bus/mhi/ep/ring.c
index 405ce16c02a89ea2268ea1033ff5c1c26b1c81bd..a369c1eb0c0b849d7ced01b99898ca461cf680b9 100644
--- a/drivers/bus/mhi/ep/ring.c
+++ b/drivers/bus/mhi/ep/ring.c
@@ -30,7 +30,6 @@ static int __mhi_ep_cache_ring(struct mhi_ep_ring *ring, size_t end)
 {
 	struct mhi_ep_cntrl *mhi_cntrl = ring->mhi_cntrl;
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
-	struct mhi_ep_buf_info buf_info = {};
 	size_t start;
 	int ret;
 
@@ -44,6 +43,8 @@ static int __mhi_ep_cache_ring(struct mhi_ep_ring *ring, size_t end)
 
 	start = ring->wr_offset;
 	if (start < end) {
+		struct mhi_ep_buf_info buf_info = {};
+
 		buf_info.size = (end - start) * sizeof(struct mhi_ring_element);
 		buf_info.host_addr = ring->rbase + (start * sizeof(struct mhi_ring_element));
 		buf_info.dev_addr = &ring->ring_cache[start];
@@ -51,27 +52,30 @@ static int __mhi_ep_cache_ring(struct mhi_ep_ring *ring, size_t end)
 		ret = mhi_cntrl->read_sync(mhi_cntrl, &buf_info);
 		if (ret)
 			return ret;
+
+		dev_dbg(dev, "Cached ring: start %zu end %zu size %zu\n", start, end,
+			buf_info.size);
 	} else {
-		buf_info.size = (ring->ring_size - start) * sizeof(struct mhi_ring_element);
-		buf_info.host_addr = ring->rbase + (start * sizeof(struct mhi_ring_element));
-		buf_info.dev_addr = &ring->ring_cache[start];
+		struct mhi_ep_buf_info buf_info[2] = {};
+		u32 count = 1;
 
-		ret = mhi_cntrl->read_sync(mhi_cntrl, &buf_info);
-		if (ret)
-			return ret;
+		buf_info[0].size = (ring->ring_size - start) * sizeof(struct mhi_ring_element);
+		buf_info[0].host_addr = ring->rbase + (start * sizeof(struct mhi_ring_element));
+		buf_info[0].dev_addr = &ring->ring_cache[start];
 
 		if (end) {
-			buf_info.host_addr = ring->rbase;
-			buf_info.dev_addr = &ring->ring_cache[0];
-			buf_info.size = end * sizeof(struct mhi_ring_element);
-
-			ret = mhi_cntrl->read_sync(mhi_cntrl, &buf_info);
-			if (ret)
-				return ret;
+			buf_info[1].size = end * sizeof(struct mhi_ring_element);
+			buf_info[1].host_addr = ring->rbase;
+			buf_info[1].dev_addr = &ring->ring_cache[0];
+			count = 2;
 		}
-	}
+		ret = mhi_cntrl->read_batch(mhi_cntrl, buf_info, count);
+		if (ret)
+			return ret;
 
-	dev_dbg(dev, "Cached ring: start %zu end %zu size %zu\n", start, end, buf_info.size);
+		dev_dbg(dev, "Cached ring (batched): start %zu end %zu tail_size %zu head_size %zu count %u\n",
+			start, end, buf_info[0].size, end ? buf_info[1].size : 0, count);
+	}
 
 	return 0;
 }

-- 
2.34.1