[PATCH] drm/mcde: Fix stability issue

* [PATCH] drm/mcde: Fix stability issue
@ 2020-07-18 23:33 Linus Walleij
  2020-07-21 14:20 ` Sasha Levin
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Linus Walleij @ 2020-07-18 23:33 UTC (permalink / raw)
  To: dri-devel, Maarten Lankhorst, Maxime Ripard, Sean Paul
  Cc: linux-arm-kernel, Linus Walleij, Stephan Gerhold, stable

Whenener a display update was sent, apart from updating
the memory base address we called mcde_display_send_one_frame()
which also sent a command to the display requesting the TE IRQ
and enabling the FIFO.

When continous updates are running this is wrong: we need
to only send this to start the flow to the display on
the very first update. This lead to the display pipeline
locking up and crashing.

Check if the flow is already running and in that case
do not call mcde_display_send_one_frame().

This fixes crashes on the Samsung GT-S7710 (Skomer).

Cc: Stephan Gerhold <stephan@gerhold.net>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpu/drm/mcde/mcde_display.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/mcde/mcde_display.c b/drivers/gpu/drm/mcde/mcde_display.c
index 212aee60cf61..1d8ea8830a17 100644
--- a/drivers/gpu/drm/mcde/mcde_display.c
+++ b/drivers/gpu/drm/mcde/mcde_display.c
@@ -1086,9 +1086,14 @@ static void mcde_display_update(struct drm_simple_display_pipe *pipe,
 	 */
 	if (fb) {
 		mcde_set_extsrc(mcde, drm_fb_cma_get_gem_addr(fb, pstate, 0));
-		if (!mcde->video_mode)
-			/* Send a single frame using software sync */
-			mcde_display_send_one_frame(mcde);
+		if (!mcde->video_mode) {
+			/*
+			 * Send a single frame using software sync if the flow
+			 * is not active yet.
+			 */
+			if (mcde->flow_active == 0)
+				mcde_display_send_one_frame(mcde);
+		}
 		dev_info_once(mcde->dev, "sent first display update\n");
 	} else {
 		/*
-- 
2.26.2


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