[PATCH 1/1] drm/imx/ipuv-v3: Fix front porch adjustment upon hactive aligning

[Ian Ray]

On Wed, May 03, 2023 at 01:14:56PM +0200, Alexander Stein wrote:
> 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 at ew.tq-group.com>

Tested on the same 1366x768 display hardware that required the original                                                                                                                                                                                                         
fix in commit 94dfec48fca7.                                                                                                                                                                                                                                                     
                                                                                                                                                                                                                                                                                
Tested-by: Ian Ray <ian.ray at ge.com>                                                                                                                                                                                                                                             


> ---
> AFAICS ipu_di_adjust_videomode() checks that front porch is big enough to
> reduce the alignment difference.
> 
>  drivers/gpu/drm/imx/ipuv3/ipuv3-crtc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/imx/ipuv3/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3/ipuv3-crtc.c
> index 1d306f7be9fd..341e9125bf2c 100644
> --- a/drivers/gpu/drm/imx/ipuv3/ipuv3-crtc.c
> +++ b/drivers/gpu/drm/imx/ipuv3/ipuv3-crtc.c
> @@ -311,7 +311,7 @@ static void ipu_crtc_mode_set_nofb(struct drm_crtc *crtc)
>                          sig_cfg.mode.hactive, new_hactive);
>  
>                 dev_info(ipu_crtc->dev, "hfront_porch: %u\n", sig_cfg.mode.hfront_porch);
> -               sig_cfg.mode.hfront_porch = new_hactive - sig_cfg.mode.hactive;
> +               sig_cfg.mode.hfront_porch -= new_hactive - sig_cfg.mode.hactive;
>                 dev_info(ipu_crtc->dev, "hfront_porch: %u\n", sig_cfg.mode.hfront_porch);
>                 sig_cfg.mode.hactive = new_hactive;
>         }
> -- 
> 2.34.1
>