linux-kernel - [PATCH v2 2/2] drm/msm/dsi: fix 32-bit signed integer extension in pclk

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Message-ID: <20241007050157.26855-2-jonathan@marek.ca>
Date: Mon,  7 Oct 2024 01:01:49 -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>,
	Sibi Sankar <quic_sibis@...cinc.com>,
	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 2/2] drm/msm/dsi: fix 32-bit signed integer extension in pclk_rate calculation

When (mode->clock * 1000) is larger than (1<<31), int to unsigned long
conversion will sign extend the int to 64 bits and the pclk_rate value
will be incorrect.

Fix this by making the result of the multiplication unsigned.

Note that above (1<<32) would still be broken and require more changes, but
its unlikely anyone will need that anytime soon.

Fixes: c4d8cfe516dc ("drm/msm/dsi: add implementation for helper functions")
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 1205aa398e445..a98d24b7cb00b 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -550,7 +550,7 @@ static unsigned long dsi_get_pclk_rate(const struct drm_display_mode *mode,
 {
 	unsigned long pclk_rate;
 
-	pclk_rate = mode->clock * 1000;
+	pclk_rate = mode->clock * 1000u;
 
 	if (dsc)
 		pclk_rate = dsi_adjust_pclk_for_compression(mode, dsc);
-- 
2.45.1