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Message-ID: <7d5a8d4e8648540b7d644c1614b169ddd7ceaab5.camel@mediatek.com>
Date: Fri, 19 Dec 2025 17:00:24 +0000
From: Paul-pl Chen (陳柏霖) <Paul-pl.Chen@...iatek.com>
To: CK Hu (胡俊光) <ck.hu@...iatek.com>,
"robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
<krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>, "AngeloGioacchino Del
Regno" <angelogioacchino.delregno@...labora.com>
CC: Sunny Shen (沈姍姍) <Sunny.Shen@...iatek.com>,
Sirius Wang (王皓昱) <Sirius.Wang@...iatek.com>,
Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
Xiandong Wang (王先冬)
<Xiandong.Wang@...iatek.com>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, Project_Global_Chrome_Upstream_Group
<Project_Global_Chrome_Upstream_Group@...iatek.com>,
"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"fshao@...omium.org" <fshao@...omium.org>, "p.zabel@...gutronix.de"
<p.zabel@...gutronix.de>, Singo Chang (張興國)
<Singo.Chang@...iatek.com>, "linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, "matthias.bgg@...il.com"
<matthias.bgg@...il.com>, "treapking@...omium.org" <treapking@...omium.org>
Subject: Re: [PATCH v4 13/19] drm/mediatek: Export OVL Blend function
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@...iatek.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@...iatek.com>
> > Signed-off-by: Paul-pl Chen <paul-pl.chen@...iatek.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,
>
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