From: Rob Clark <robdcl...@chromium.org>

[ Upstream commit 174974d8463b77c2b4065e98513adb204e64de7d ]

If the previous thing cat'ing $debugfs/rd left the FIFO full, then
subsequent open could deadlock in rd_write() (because open is blocked,
not giving a chance for read() to consume any data in the FIFO).  Also
it is generally a good idea to clear out old data from the FIFO.

Signed-off-by: Rob Clark <robdcl...@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/496706/
Link: https://lore.kernel.org/r/20220807160901.2353471-2-robdcl...@gmail.com
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/gpu/drm/msm/msm_rd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/msm/msm_rd.c b/drivers/gpu/drm/msm/msm_rd.c
index c7832a951039f..a6b024b06b363 100644
--- a/drivers/gpu/drm/msm/msm_rd.c
+++ b/drivers/gpu/drm/msm/msm_rd.c
@@ -191,6 +191,9 @@ static int rd_open(struct inode *inode, struct file *file)
        file->private_data = rd;
        rd->open = true;
 
+       /* Reset fifo to clear any previously unread data: */
+       rd->fifo.head = rd->fifo.tail = 0;
+
        /* the parsing tools need to know gpu-id to know which
         * register database to load.
         */
-- 
2.35.1

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