[PATCH v3 1/4] bus: mhi: host: Add spinlock to protect WP access when queueing TREs

[Qiang Yu <quic_qianyu@xxxxxxxxxxx>]

From: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>

Protect WP accesses such that multiple threads queueing buffers for
incoming data do not race.

Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 189ff97cca53 ("bus: mhi: core: Add support for data transfer")
Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
Signed-off-by: Qiang Yu <quic_qianyu@xxxxxxxxxxx>
---
 drivers/bus/mhi/host/main.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index 6cf1145..c9415b0 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -1205,6 +1205,9 @@ int mhi_gen_tre(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan,
 	int eot, eob, chain, bei;
 	int ret;
 
+	/* Protect accesses for reading and incrementing WP */
+	write_lock_bh(&mhi_chan->lock);
+
 	buf_ring = &mhi_chan->buf_ring;
 	tre_ring = &mhi_chan->tre_ring;
 
@@ -1222,8 +1225,10 @@ int mhi_gen_tre(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan,
 
 	if (!info->pre_mapped) {
 		ret = mhi_cntrl->map_single(mhi_cntrl, buf_info);
-		if (ret)
+		if (ret) {
+			write_unlock_bh(&mhi_chan->lock);
 			return ret;
+		}
 	}
 
 	eob = !!(flags & MHI_EOB);
@@ -1240,6 +1245,8 @@ int mhi_gen_tre(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan,
 	mhi_add_ring_element(mhi_cntrl, tre_ring);
 	mhi_add_ring_element(mhi_cntrl, buf_ring);
 
+	write_unlock_bh(&mhi_chan->lock);
+
 	return 0;
 }
 
-- 
2.7.4