linux-kernel - [PATCH 5.10 22/67] drm/amd/display: ensure dentist display clock update finished in DCN20

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Date:   Mon,  2 Aug 2021 15:44:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Cyr Aric <aric.cyr@....com>,
        Solomon Chiu <solomon.chiu@....com>,
        Dale Zhao <dale.zhao@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Alex Deucher <alexander.deucher@....com>
Subject: [PATCH 5.10 22/67] drm/amd/display: ensure dentist display clock update finished in DCN20

From: Dale Zhao <dale.zhao@....com>

commit b53e041d8e4308f7324999398aec092dbcb130f5 upstream.

[Why]
We don't check DENTIST_DISPCLK_CHG_DONE to ensure dentist
display clockis updated to target value. In some scenarios with large
display clock margin, it will deliver unfinished display clock and cause
issues like display black screen.

[How]
Checking DENTIST_DISPCLK_CHG_DONE to ensure display clock
has been update to target value before driver do other clock related
actions.

Reviewed-by: Cyr Aric <aric.cyr@....com>
Acked-by: Solomon Chiu <solomon.chiu@....com>
Signed-off-by: Dale Zhao <dale.zhao@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/amd/display/dc/clk_mgr/dcn20/dcn20_clk_mgr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn20/dcn20_clk_mgr.c
+++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn20/dcn20_clk_mgr.c
@@ -135,7 +135,7 @@ void dcn20_update_clocks_update_dentist(
 
 	REG_UPDATE(DENTIST_DISPCLK_CNTL,
 			DENTIST_DISPCLK_WDIVIDER, dispclk_wdivider);
-//	REG_WAIT(DENTIST_DISPCLK_CNTL, DENTIST_DISPCLK_CHG_DONE, 1, 5, 100);
+	REG_WAIT(DENTIST_DISPCLK_CNTL, DENTIST_DISPCLK_CHG_DONE, 1, 50, 1000);
 	REG_UPDATE(DENTIST_DISPCLK_CNTL,
 			DENTIST_DPPCLK_WDIVIDER, dppclk_wdivider);
 	REG_WAIT(DENTIST_DISPCLK_CNTL, DENTIST_DPPCLK_CHG_DONE, 1, 5, 100);