linux-kernel - [PATCH v2 1/2] drm/msm/dsi: improve/fix dsc pclk calculation

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Message-ID: <20241007050157.26855-1-jonathan@marek.ca>
Date: Mon,  7 Oct 2024 01:01:48 -0400
From: Jonathan Marek <jonathan@...ek.ca>
To: freedreno@...ts.freedesktop.org
Cc: Rob Clark <robdclark@...il.com>,
	Abhinav Kumar <quic_abhinavk@...cinc.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Sean Paul <sean@...rly.run>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Jessica Zhang <quic_jesszhan@...cinc.com>,
	Konrad Dybcio <konradybcio@...nel.org>,
	linux-arm-msm@...r.kernel.org (open list:DRM DRIVER for Qualcomm display hardware),
	dri-devel@...ts.freedesktop.org (open list:DRM DRIVER for Qualcomm display hardware),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 1/2] drm/msm/dsi: improve/fix dsc pclk calculation

drm_mode_vrefresh() can introduce a large rounding error, avoid it.

Fixes: 7c9e4a554d4a ("drm/msm/dsi: Reduce pclk rate for compression")
Signed-off-by: Jonathan Marek <jonathan@...ek.ca>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 185d7de0bf376..1205aa398e445 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -542,7 +542,7 @@ static unsigned long dsi_adjust_pclk_for_compression(const struct drm_display_mo
 
 	int new_htotal = mode->htotal - mode->hdisplay + new_hdisplay;
 
-	return new_htotal * mode->vtotal * drm_mode_vrefresh(mode);
+	return mult_frac(mode->clock * 1000u, new_htotal, mode->htotal);
 }
 
 static unsigned long dsi_get_pclk_rate(const struct drm_display_mode *mode,
-- 
2.45.1