[PATCH] drm/mediatek: Fix XRGB format breakage for blend_modes unsupported SoCs

[Jason-JH Lin (林睿祥)]

Hi CK,

On Mon, 2024-10-07 at 05:57 +0000, CK Hu (胡俊光) wrote:
> Hi, Jason:
> 
> On Sat, 2024-10-05 at 17:52 +0800, Jason-JH.Lin wrote:
> > If the constant alpha always set, the SoCs that is not supported
> > the
> > ignore alpha bit will still use constant alpha. That will break the
> > original constant alpha setting of XRGB foramt for blend_modes
> > unsupported SoCs, such as MT8173.
> > 
> > Make the constatnt alpha only set when setting has_alpha or
> > supported
> > blend_modes SoC to fix the downgrade issue.
> 
> I would like this patch to be cherry-picked to kernel 6.11 easily, so
> let this patch base on 6.12-rc1.

OK, I'll move this patch in front of this series:
[1] Fix degradation problem of alpha blending series
- 
https://patchwork.kernel.org/project/linux-mediatek/list/?series=893634
and then send v9 to let you cherry-pick it to kernel-6.11 easily.

> 
> > 
> > Fixes: bc46eb5d5d77 ("drm/mediatek: Support DRM plane alpha in
> > OVL")
> > Signed-off-by: Jason-JH.Lin <jason-jh.lin at mediatek.com>
> > ---
> >  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 28 +++++++++++++++----
> > ------
> >  1 file changed, 17 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > index 703cd3f6c6d3..de3addd89442 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > @@ -494,19 +494,25 @@ void mtk_ovl_layer_config(struct device *dev,
> > unsigned int idx,
> >  
> >  	con = mtk_ovl_fmt_convert(ovl, state);
> >  	if (state->base.fb) {
> > -		con |= OVL_CON_AEN;
> > -		con |= state->base.alpha & OVL_CON_ALPHA;
> > +		/*
> > +		 * For blend_modes supported SoCs, always set constant
> > alpha.
> > +		 * For blend_modes unsupported SoCs, set constant alpha
> > when has_alpha is set.
> > +		 */
> > +		if (ovl->data->blend_modes || state->base.fb->format-
> > >has_alpha) {
> > +			con |= OVL_CON_AEN;
> > +			con |= state->base.alpha & OVL_CON_ALPHA;
> 
> MT8173 does not support ignore pixel alpha, so OVL_CON_AEN would be
> disabled for XRGB.
> And this is not related to plane alpha, so plane alpha setting should
> be moved out of here.

OK, that make sense.
But I would like to ask Yassine and Adam to test this change again.

> 
> > +		}
> > +
> > +		/*
> > +		 * Although the alpha channel can be ignored, CONST_BLD
> > must be enabled
> > +		 * for XRGB format, otherwise OVL will still read the
> > value from memory.
> > +		 * For RGB888 related formats, whether CONST_BLD is
> > enabled or not won't
> > +		 * affect the result. Therefore we use !has_alpha as
> > the condition.
> > +		 */
> > +		if (blend_mode == DRM_MODE_BLEND_PIXEL_NONE || !state-
> > >base.fb->format->has_alpha)
> > +			ignore_pixel_alpha = OVL_CONST_BLEND;
> 
> This modification is not related to the bug fix, so separate to
> another patch.

OK, I'll separate it.

Regards,
Jason-JH.Lin

> 
> Regards,
> CK