linux-kernel - [PATCH] drm/drm_vblank.c: avoid unsigned int to signed int cast

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Date:   Wed, 17 May 2023 01:30:26 +0800
From:   Sui Jingfeng <15330273260@....cn>
To:     Sui Jingfeng <suijingfeng@...ngson.cn>, Li Yi <liyi@...ngson.cn>
Cc:     Thomas Zimmermann <tzimmermann@...e.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: [PATCH] drm/drm_vblank.c: avoid unsigned int to signed int cast

From: Sui Jingfeng <suijingfeng@...ngson.cn>

Both mode->crtc_htotal and mode->crtc_vtotal are u16 type,
mode->crtc_htotal * mode->crtc_vtotal will results a unsigned type.
Using a u32 is enough to store the result, but considering that the
result will be casted to u64 soon after. We use a u64 type directly.
So there no need to cast it to signed type and cast back then.

Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Maxime Ripard <mripard@...nel.org>
Cc: Thomas Zimmermann <tzimmermann@...e.de>
Cc: David Airlie <airlied@...il.com>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: dri-devel@...ts.freedesktop.org
Cc: linux-kernel@...r.kernel.org
Cc: loongson-kernel@...ts.loongnix.cn
---
 drivers/gpu/drm/drm_vblank.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 877e2067534f..d99c404b181b 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -622,7 +622,7 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 
 	/* Valid dotclock? */
 	if (dotclock > 0) {
-		int frame_size = mode->crtc_htotal * mode->crtc_vtotal;
+		u64 frame_size = mode->crtc_htotal * mode->crtc_vtotal;
 
 		/*
 		 * Convert scanline length in pixels and video
@@ -630,7 +630,7 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 		 * in nanoseconds:
 		 */
 		linedur_ns  = div_u64((u64) mode->crtc_htotal * 1000000, dotclock);
-		framedur_ns = div_u64((u64) frame_size * 1000000, dotclock);
+		framedur_ns = div_u64(frame_size * 1000000, dotclock);
 
 		/*
 		 * Fields of interlaced scanout modes are only half a frame duration.
-- 
2.25.1