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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Maxime Ripard <maxime.ripard@bootlin.com>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 275/276] drm/sun4i: dsi: Enforce boundaries on the start delay
Date:   Wed, 29 May 2019 20:07:13 -0700
Message-Id: <20190530030542.392185247@linuxfoundation.org>
In-Reply-To: <20190530030523.133519668@linuxfoundation.org>
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[ Upstream commit efa31801203ac2f5c6a82a28cb991c7163ee0f1d ]

The Allwinner BSP makes sure that we don't end up with a null start delay
or with a delay larger than vtotal.

The former condition is likely to happen now with the reworked start delay,
so make sure we enforce the same boundaries.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/c9889cf5f7a3d101ef380905900b45a182596f56.1549896081.git-series.maxime.ripard@bootlin.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 3de41de43127b..97a0573cc5145 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -358,8 +358,12 @@ static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
 					   struct drm_display_mode *mode)
 {
 	u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100);
+	u16 delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
 
-	return mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
+	if (delay > mode->vtotal)
+		delay = delay % mode->vtotal;
+
+	return max_t(u16, delay, 1);
 }
 
 static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
-- 
2.20.1