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 5f26090b0c9850a541d563d0648e103a50f72816..89585b31b985e182948d1a3838f21e10b7941ffb 100644 (file)
--- a/drivers/gpu/drm/imx/ipuv3-crtc.c
+++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
@@ -310,7 +310,7 @@ 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;
        }