drm/imx/ipuv3: Fix front porch adjustment upon hactive aligning

[ Upstream commit ee31742bf17636da1304af77b2cb1c29b5dda642 ]

When hactive is not aligned to 8 pixels, it is aligned accordingly and
hfront porch needs to be reduced the same amount. Unfortunately the front
porch is set to the difference rather than reducing it. There are some
Samsung TVs which can't cope with a front porch of instead of 70.

Fixes: 94dfec48fca7 ("drm/imx: Add 8 pixel alignment fix")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20230515072137.116211-1-alexander.stein@ew.tq-group.com
[p.zabel@pengutronix.de: Fixed subject]
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230515072137.116211-1-alexander.stein@ew.tq-group.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/imx/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3-crtc.c
index f7863d6dea80484497ef091efacd39d320b3f817..ba5b16618c23750cd65e487f5ae34cb2e94abe61 100644 (file)
--- a/drivers/gpu/drm/imx/ipuv3-crtc.c
+++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
@@ -311,7 +311,7 @@ static void ipu_crtc_mode_set_nofb(struct drm_crtc *crtc)
                dev_warn(ipu_crtc->dev, "8-pixel align hactive %d -> %d\n",
                         sig_cfg.mode.hactive, new_hactive);
 
-               sig_cfg.mode.hfront_porch = new_hactive - sig_cfg.mode.hactive;
+               sig_cfg.mode.hfront_porch -= new_hactive - sig_cfg.mode.hactive;
                sig_cfg.mode.hactive = new_hactive;
        }