linux-kernel - [PATCH AUTOSEL 6.10 078/121] drm/amd/display: Disable DMCUB timeout for DCN35

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Message-ID: <20240801000834.3930818-78-sashal@kernel.org>
Date: Wed, 31 Jul 2024 20:00:16 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
	Ovidiu Bunea <ovidiu.bunea@....com>,
	Zaeem Mohamed <zaeem.mohamed@....com>,
	Daniel Wheeler <daniel.wheeler@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>,
	harry.wentland@....com,
	sunpeng.li@....com,
	Rodrigo.Siqueira@....com,
	christian.koenig@....com,
	Xinhui.Pan@....com,
	airlied@...il.com,
	daniel@...ll.ch,
	charlene.liu@....com,
	Qingqing.Zhuo@....com,
	wayne.lin@....com,
	ahmed.ahmed@....com,
	wenjing.liu@....com,
	daniel.miess@....com,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.10 078/121] drm/amd/display: Disable DMCUB timeout for DCN35

From: Nicholas Kazlauskas <nicholas.kazlauskas@....com>

[ Upstream commit 7c70e60fbf4bff1123f0e8d5cb1ae71df6164d7f ]

[Why]
DMCUB can intermittently take longer than expected to process commands.

Old ASIC policy was to continue while logging a diagnostic error - which
works fine for ASIC without IPS, but with IPS this could lead to a race
condition where we attempt to access DCN state while it's inaccessible,
leading to a system hang when the NIU port is not disabled or register
accesses that timeout and the display configuration in an undefined
state.

[How]
We need to investigate why these accesses take longer than expected, but
for now we should disable the timeout on DCN35 to avoid this race
condition. Since the waits happen only at lower interrupt levels the
risk of taking too long at higher IRQ and causing a system watchdog
timeout are minimal.

Reviewed-by: Ovidiu Bunea <ovidiu.bunea@....com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@....com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
index 28c4599076989..915d68cc04e9c 100644
--- a/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
@@ -785,6 +785,7 @@ static const struct dc_debug_options debug_defaults_drv = {
 	.ips2_entry_delay_us = 800,
 	.disable_dmub_reallow_idle = false,
 	.static_screen_wait_frames = 2,
+	.disable_timeout = true,
 };
 
 static const struct dc_panel_config panel_config_defaults = {
-- 
2.43.0