linux-kernel - [PATCH AUTOSEL 5.17 35/49] drm/amd/display: Correct Slice reset calculation

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Date:   Mon, 11 Apr 2022 20:43:53 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Chris Park <Chris.Park@....com>, Wenjing Liu <Wenjing.Liu@....com>,
        Alex Hung <alex.hung@....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@...ux.ie,
        daniel@...ll.ch, wenjing.liu@....com, wayne.lin@....com,
        mikita.lipski@....com, MarkAlbert.Morra@....com,
        tzimmermann@...e.de, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.17 35/49] drm/amd/display: Correct Slice reset calculation

From: Chris Park <Chris.Park@....com>

[ Upstream commit 862a876c3a6372f2fa9d0c6510f1976ac94fc857 ]

[Why]
Once DSC slice cannot fit pixel clock, we incorrectly
reset min slices to 0 and allow max slice to operate,
even when max slice itself cannot fit the pixel clock
properly.

[How]
Change the sequence such that we correctly determine
DSC is not possible when both min slices and max
slices cannot fit pixel clock per slice.

Reviewed-by: Wenjing Liu <Wenjing.Liu@....com>
Acked-by: Alex Hung <alex.hung@....com>
Signed-off-by: Chris Park <Chris.Park@....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/dsc/dc_dsc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
index 9c74564cbd8d..8973d3a38f9c 100644
--- a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
+++ b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
@@ -864,11 +864,11 @@ static bool setup_dsc_config(
 		min_slices_h = inc_num_slices(dsc_common_caps.slice_caps, min_slices_h);
 	}
 
+	is_dsc_possible = (min_slices_h <= max_slices_h);
+
 	if (pic_width % min_slices_h != 0)
 		min_slices_h = 0; // DSC TODO: Maybe try increasing the number of slices first?
 
-	is_dsc_possible = (min_slices_h <= max_slices_h);
-
 	if (min_slices_h == 0 && max_slices_h == 0)
 		is_dsc_possible = false;
 
-- 
2.35.1