[PATCH v4 3/5] drm/vc4: dsi: Rate-limit error interrupt messages

[Henry Zhang]

The error interrupts (contention, sequence and timeout errors) are
always enabled and each one is logged with drm_err() from the interrupt
handler. When a peripheral leaves the data lanes in a bad state, the
same error is raised again as soon as it is acknowledged. On a
Raspberry Pi 4 a "data lane 0 sequence error" was seen at more than
50000 interrupts per second; printing every one of them, mostly to a
serial console, starved the rest of the system to the point that the
SD card driver timed out and the board had to be reset.

Use drm_err_ratelimited() so that the errors stay visible without
taking the system down.

Signed-off-by: Henry Zhang <henryzhang62@xxxxxxxxx>
---
 drivers/gpu/drm/vc4/vc4_dsi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index 1eea60aec..be9caaf50 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -1487,8 +1487,8 @@ static void dsi_handle_error(struct vc4_dsi *dsi,
 	if (!(stat & bit))
 		return;
 
-	drm_err(dsi->bridge.dev, "DSI%d: %s error\n", dsi->variant->port,
-		type);
+	drm_err_ratelimited(dsi->bridge.dev, "DSI%d: %s error\n",
+			    dsi->variant->port, type);
 	*ret = IRQ_HANDLED;
 }
 
-- 
2.47.3