Re: [PATCH v4 13/19] drm/mediatek: Export OVL Blend function

["Paul-pl Chen (陳柏霖)" <Paul-pl.Chen@mediatek.com>]

On Wed, 2025-09-10 at 09:18 +0000, CK Hu (胡俊光) wrote:
> On Thu, 2025-08-28 at 16:07 +0800, Paul Chen wrote:
> > From: Paul-pl Chen <paul-pl.chen@mediatek.com>
> > 
> > For the new BLENDER component, the OVL ignore pixel alpha logic
> > should be exported as a function and reused it.
> > 
> > Signed-off-by: Nancy Lin <nancy.lin@mediatek.com>
> > Signed-off-by: Paul-pl Chen <paul-pl.chen@mediatek.com>
> > ---
> >  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 68 +++++++++++++++++----
> > ----
> >  drivers/gpu/drm/mediatek/mtk_disp_ovl.h |  8 +++
> >  2 files changed, 56 insertions(+), 20 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > index e3ee3f60f4ba..7cd3978beb98 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > @@ -228,6 +228,23 @@ void mtk_ovl_disable_vblank(struct device
> > *dev)
> >  	writel_relaxed(0x0, ovl->regs + DISP_REG_OVL_INTEN);
> >  }
> >  
> > +bool mtk_ovl_is_ignore_pixel_alpha(struct mtk_plane_state *state,
> > unsigned int blend_mode)
> > +{
> > +	if (!state->base.fb)
> > +		return false;
> > +
> > +	/*
> > +	 * 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)
> > +		return true;
> > +
> > +	return false;
> > +}
> > +
> >  u32 mtk_ovl_get_blend_modes(struct device *dev)
> >  {
> >  	struct mtk_disp_ovl *ovl = dev_get_drvdata(dev);
> > @@ -414,6 +431,29 @@ void mtk_ovl_layer_off(struct device *dev,
> > unsigned int idx,
> >  		      DISP_REG_OVL_RDMA_CTRL(idx));
> >  }
> >  
> > +unsigned int mtk_ovl_get_blend_mode(struct mtk_plane_state *state,
> > unsigned int blend_modes)
> > +{
> > +	unsigned int blend_mode = DRM_MODE_BLEND_COVERAGE;
> > +
> > +	/*
> > +	 * For the platforms where OVL_CON_CLRFMT_MAN is defined
> > in the hardware data sheet
> > +	 * and supports premultiplied color formats, such as
> > OVL_CON_CLRFMT_PARGB888
> > +	 * and supports premultiplied color formats, such as
> > OVL_CON_CLRFMT_PARGB8888.
> > +	 *
> > +	 * Check blend_modes in the driver data to see if
> > premultiplied mode is supported.
> > +	 * If not, use coverage mode instead to set it to the
> > supported color formats.
> > +	 *
> > +	 * Current DRM assumption is that alpha is default
> > premultiplied, so the bitmask of
> > +	 * blend_modes must include BIT(DRM_MODE_BLEND_PREMULTI).
> > Otherwise, mtk_plane_init()
> > +	 * will get an error return from
> > drm_plane_create_blend_mode_property() and
> > +	 * state->base.pixel_blend_mode should not be used.
> > +	 */
> > +	if (blend_modes & BIT(DRM_MODE_BLEND_PREMULTI))
> > +		blend_mode = state->base.pixel_blend_mode;
> > +
> > +	return blend_mode;
> > +}
> > +
> >  unsigned int mtk_ovl_fmt_convert(unsigned int fmt, unsigned int
> > blend_mode,
> >  				 bool fmt_rgb565_is_0, bool
> > color_convert,
> >  				 u8 clrfmt_shift, u32 clrfmt_man,
> > u32 byte_swap, u32 rgb_swap)
> > @@ -541,7 +581,7 @@ void mtk_ovl_layer_config(struct device *dev,
> > unsigned int idx,
> >  	unsigned int rotation = pending->rotation;
> >  	unsigned int offset = (pending->y << 16) | pending->x;
> >  	unsigned int src_size = (pending->height << 16) | pending-
> > >width;
> > -	unsigned int blend_mode = state->base.pixel_blend_mode;
> > +	unsigned int blend_mode = mtk_ovl_get_blend_mode(state,
> > ovl->data->blend_modes);
> 
> Why you change behavior here?
> Originally, 'blend_mode = state->base.pixel_blend_mode' directly.
> But this patch add a check and blend_mode may be
> DRM_MODE_BLEND_COVERAGE.
> The behavior changes. Why change this behavior?
> 
It's for convenient to optimize the logic design. 
> >  	unsigned int ignore_pixel_alpha = 0;
> >  	unsigned int con;
> >  
> > @@ -566,17 +606,8 @@ void mtk_ovl_layer_config(struct device *dev,
> > unsigned int idx,
> >  		 * For blend_modes supported SoCs, always enable
> > alpha blending.
> >  		 * For blend_modes unsupported SoCs, enable alpha
> > blending when has_alpha is set.
> >  		 */
> > -		if (blend_mode || state->base.fb->format-
> > >has_alpha)
> > +		if (state->base.pixel_blend_mode || state-
> > >base.fb->format->has_alpha)
> >  			con |= OVL_CON_AEN;
> > -
> > -		/*
> > -		 * 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;
> >  	}
> >  
> >  	/*
> > @@ -602,6 +633,9 @@ void mtk_ovl_layer_config(struct device *dev,
> > unsigned int idx,
> >  
> >  	mtk_ddp_write_relaxed(cmdq_pkt, con, &ovl->cmdq_reg, ovl-
> > >regs,
> >  			      DISP_REG_OVL_CON(idx));
> > +
> > +	if (mtk_ovl_is_ignore_pixel_alpha(state, blend_mode))
> > +		ignore_pixel_alpha = OVL_CONST_BLEND;
> >  	mtk_ddp_write_relaxed(cmdq_pkt, pitch_lsb |
> > ignore_pixel_alpha,
> >  			      &ovl->cmdq_reg, ovl->regs,
> > DISP_REG_OVL_PITCH(idx));
> >  	mtk_ddp_write_relaxed(cmdq_pkt, src_size, &ovl->cmdq_reg,
> > ovl->regs,
>