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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Wenjing Liu <Wenjing.Liu@amd.com>,
        Alex Hung <alex.hung@amd.com>, Chris Park <Chris.Park@amd.com>,
        Daniel Wheeler <daniel.wheeler@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.17 162/219] drm/amd/display: Correct Slice reset calculation
Date:   Mon, 18 Apr 2022 14:12:11 +0200
Message-Id: <20220418121211.417970399@linuxfoundation.org>
In-Reply-To: <20220418121203.462784814@linuxfoundation.org>
References: <20220418121203.462784814@linuxfoundation.org>
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From: Chris Park <Chris.Park@amd.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@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Chris Park <Chris.Park@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.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