linux-kernel - [PATCH AUTOSEL 6.12 372/486] drm/amd/display: Use Nominal vBlank If Provided Instead Of Capping It

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Message-Id: <20250505223922.2682012-372-sashal@kernel.org>
Date: Mon,  5 May 2025 18:37:28 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Austin Zheng <Austin.Zheng@....com>,
	Dillon Varone <dillon.varone@....com>,
	Wayne Lin <wayne.lin@....com>,
	Daniel Wheeler <daniel.wheeler@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>,
	austin.zheng@....com,
	jun.lei@....com,
	harry.wentland@....com,
	sunpeng.li@....com,
	christian.koenig@....com,
	airlied@...il.com,
	simona@...ll.ch,
	siqueira@...lia.com,
	alex.hung@....com,
	colin.i.king@...il.com,
	aurabindo.pillai@....com,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.12 372/486] drm/amd/display: Use Nominal vBlank If Provided Instead Of Capping It

From: Austin Zheng <Austin.Zheng@....com>

[ Upstream commit 41df56b1fc24cc36fffb10e437385b3a49fbb5e2 ]

[Why/How]
vBlank used to determine the max vStartup is based on the smallest between
the vblank provided by the timing and vblank in ip_caps.
Extra vblank time is not considered if the vblank provided by the timing ends
up being higher than what's defined by the ip_caps

Use 1 less than the vblank size in case the timing is interlaced
so vstartup will always be less than vblank_nom.

Reviewed-by: Dillon Varone <dillon.varone@....com>
Signed-off-by: Austin Zheng <Austin.Zheng@....com>
Signed-off-by: Wayne Lin <wayne.lin@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c       | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c b/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c
index e2a3764d9d181..0090b7bc232bf 100644
--- a/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c
+++ b/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c
@@ -3630,13 +3630,12 @@ static unsigned int CalculateMaxVStartup(
 	double line_time_us = (double)timing->h_total / ((double)timing->pixel_clock_khz / 1000);
 	unsigned int vblank_actual = timing->v_total - timing->v_active;
 	unsigned int vblank_nom_default_in_line = (unsigned int)math_floor2((double)vblank_nom_default_us / line_time_us, 1.0);
-	unsigned int vblank_nom_input = (unsigned int)math_min2(timing->vblank_nom, vblank_nom_default_in_line);
-	unsigned int vblank_avail = (vblank_nom_input == 0) ? vblank_nom_default_in_line : vblank_nom_input;
+	unsigned int vblank_avail = (timing->vblank_nom == 0) ? vblank_nom_default_in_line : (unsigned int)timing->vblank_nom;
 
 	vblank_size = (unsigned int)math_min2(vblank_actual, vblank_avail);
 
 	if (timing->interlaced && !ptoi_supported)
-		max_vstartup_lines = (unsigned int)(math_floor2(vblank_size / 2.0, 1.0));
+		max_vstartup_lines = (unsigned int)(math_floor2((vblank_size - 1) / 2.0, 1.0));
 	else
 		max_vstartup_lines = vblank_size - (unsigned int)math_max2(1.0, math_ceil2(write_back_delay_us / line_time_us, 1.0));
 #ifdef __DML_VBA_DEBUG__
-- 
2.39.5