[PATCH v4 1/5] drm/vc4: dsi: Set the transfer result before completing the transfer

[Henry Zhang]

On an HSTX timeout the interrupt handler completes the transfer and
only then sets xfer_result to -ETIMEDOUT. The waiter, which may run on
another CPU, can wake up and read xfer_result in between, still 0 from
the start of the transfer, and report the timed-out transfer as a
success.

Set xfer_result first. complete() orders the store before the wake-up.

Fixes: 4078f5757144 ("drm/vc4: Add DSI driver")
Signed-off-by: Henry Zhang <henryzhang62@xxxxxxxxx>
---
 drivers/gpu/drm/vc4/vc4_dsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index 5ed3c35ee..aa2b46fb0 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -1526,8 +1526,8 @@ static irqreturn_t vc4_dsi_irq_handler(int irq, void *data)
 		complete(&dsi->xfer_completion);
 		ret = IRQ_HANDLED;
 	} else if (stat & DSI_PORT_BIT(INT_HSTX_TO)) {
-		complete(&dsi->xfer_completion);
 		dsi->xfer_result = -ETIMEDOUT;
+		complete(&dsi->xfer_completion);
 		ret = IRQ_HANDLED;
 	}
 
-- 
2.47.3