linux-kernel - [PATCH AUTOSEL 4.14 174/186] radeon: insert 10ms sleep in dce5_crtc_load

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Date:   Fri, 14 Feb 2020 11:17:03 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>,
        Michel Dänzer <michel.daenzer@....com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sasha Levin <sashal@...nel.org>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 4.14 174/186] radeon: insert 10ms sleep in dce5_crtc_load_lut

From: Daniel Vetter <daniel.vetter@...ll.ch>

[ Upstream commit ec3d65082d7dabad6fa8f66a8ef166f2d522d6b2 ]

Per at least one tester this is enough magic to recover the regression
introduced for some people (but not all) in

commit b8e2b0199cc377617dc238f5106352c06dcd3fa2
Author: Peter Rosin <peda@...ntia.se>
Date:   Tue Jul 4 12:36:57 2017 +0200

    drm/fb-helper: factor out pseudo-palette

which for radeon had the side-effect of refactoring out a seemingly
redudant writing of the color palette.

10ms in a fairly slow modeset path feels like an acceptable form of
duct-tape, so maybe worth a shot and see what sticks.

Cc: Alex Deucher <alexander.deucher@....com>
Cc: Michel Dänzer <michel.daenzer@....com>
References: https://bugzilla.kernel.org/show_bug.cgi?id=198123
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/radeon/radeon_display.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 4ed80bf5d3f0d..a21647dce3bf5 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -119,6 +119,8 @@ static void dce5_crtc_load_lut(struct drm_crtc *crtc)
 
 	DRM_DEBUG_KMS("%d\n", radeon_crtc->crtc_id);
 
+	msleep(10);
+
 	WREG32(NI_INPUT_CSC_CONTROL + radeon_crtc->crtc_offset,
 	       (NI_INPUT_CSC_GRPH_MODE(NI_INPUT_CSC_BYPASS) |
 		NI_INPUT_CSC_OVL_MODE(NI_INPUT_CSC_BYPASS)));
-- 
2.20.1