linux-kernel - [PATCH 4/5] drm/sun4i: sun6i_mipi_dsi: fix horizontal timing calculation

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Message-Id: <20200311163329.221840-5-icenowy@aosc.io>
Date:   Thu, 12 Mar 2020 00:33:28 +0800
From:   Icenowy Zheng <icenowy@...c.io>
To:     Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, Ondrej Jirman <megous@...ous.com>
Cc:     dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...glegroups.com, Icenowy Zheng <icenowy@...c.io>
Subject: [PATCH 4/5] drm/sun4i: sun6i_mipi_dsi: fix horizontal timing calculation

The max() function call in horizontal timing calculation shouldn't pad a
length already subtracted with overhead to overhead, instead it should
only prevent the set timing to underflow.

Signed-off-by: Icenowy Zheng <icenowy@...c.io>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 059939789730..5f2313c40328 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -555,7 +555,7 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
 		 */
 #define HSA_PACKET_OVERHEAD	10
 		hsa = max((unsigned int)HSA_PACKET_OVERHEAD,
-			  (mode->hsync_end - mode->hsync_start) * Bpp - HSA_PACKET_OVERHEAD);
+			  (mode->hsync_end - mode->hsync_start) * Bpp) - HSA_PACKET_OVERHEAD;
 
 		/*
 		 * The backporch is set using a blanking packet (4
@@ -564,7 +564,7 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
 		 */
 #define HBP_PACKET_OVERHEAD	6
 		hbp = max((unsigned int)HBP_PACKET_OVERHEAD,
-			  (mode->htotal - mode->hsync_end) * Bpp - HBP_PACKET_OVERHEAD);
+			  (mode->htotal - mode->hsync_end) * Bpp) - HBP_PACKET_OVERHEAD;
 
 		/*
 		 * The frontporch is set using a sync event (4 bytes)
@@ -574,7 +574,7 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
 		 */
 #define HFP_PACKET_OVERHEAD	16
 		hfp = max((unsigned int)HFP_PACKET_OVERHEAD,
-			  (mode->hsync_start - mode->hdisplay) * Bpp - HFP_PACKET_OVERHEAD);
+			  (mode->hsync_start - mode->hdisplay) * Bpp) - HFP_PACKET_OVERHEAD;
 
 		/*
 		 * The blanking is set using a sync event (4 bytes)
@@ -583,8 +583,8 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
 		 */
 #define HBLK_PACKET_OVERHEAD	10
 		hblk = max((unsigned int)HBLK_PACKET_OVERHEAD,
-			   (mode->htotal - (mode->hsync_end - mode->hsync_start)) * Bpp -
-			   HBLK_PACKET_OVERHEAD);
+			   (mode->htotal - (mode->hsync_end - mode->hsync_start)) * Bpp) -
+			   HBLK_PACKET_OVERHEAD;
 
 		/*
 		 * And I'm not entirely sure what vblk is about. The driver in
-- 
2.24.1