linux-kernel - Re: [PATCH 08/30] drm/sun4i: ui layer: Write attributes in one go

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Message-ID: <CAGb2v64YkkYRqfXnOcHkn+L3xh26mSXZ+CWjzbr_KXdNmq+Jpw@mail.gmail.com>
Date: Tue, 28 Oct 2025 02:16:36 +0800
From: Chen-Yu Tsai <wens@...nel.org>
To: Jernej Škrabec <jernej.skrabec@...il.com>
Cc: mripard@...nel.org, maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de, 
	airlied@...il.com, simona@...ll.ch, samuel@...lland.org, 
	dri-devel@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org, 
	linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/30] drm/sun4i: ui layer: Write attributes in one go

On Tue, Oct 28, 2025 at 2:13 AM Jernej Škrabec <jernej.skrabec@...il.com> wrote:
>
> Dne ponedeljek, 27. oktober 2025 ob 17:04:38 Srednjeevropski standardni čas je Chen-Yu Tsai napisal(a):
> > On Mon, Oct 13, 2025 at 3:23 AM Jernej Skrabec <jernej.skrabec@...il.com> wrote:
> > >
> > > It turns out that none of the UI channel registers were meant to be
> > > read. Mostly it works fine but sometimes it returns incorrect values.
> > >
> > > Rework UI layer code to write all registers in one go to avoid reads.
> > >
> > > This rework will also allow proper code separation.
> > >
> > > Signed-off-by: Jernej Skrabec <jernej.skrabec@...il.com>
> >
> > Reviewed-by: Chen-Yu Tsai <wens@...nel.org>
> >
> > > ---
> > >  drivers/gpu/drm/sun4i/sun8i_ui_layer.c | 50 +++++++++-----------------
> > >  1 file changed, 16 insertions(+), 34 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
> > > index 12c83c54f9bc..8634d2ee613a 100644
> > > --- a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
> > > +++ b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
> > > @@ -25,25 +25,27 @@
> > >  #include "sun8i_ui_scaler.h"
> > >  #include "sun8i_vi_scaler.h"
> > >
> > > -static void sun8i_ui_layer_update_alpha(struct sun8i_mixer *mixer, int channel,
> > > -                                       int overlay, struct drm_plane *plane)
> > > +static void sun8i_ui_layer_update_attributes(struct sun8i_mixer *mixer,
> > > +                                            int channel, int overlay,
> > > +                                            struct drm_plane *plane)
> > >  {
> > > -       u32 mask, val, ch_base;
> > > +       struct drm_plane_state *state = plane->state;
> > > +       const struct drm_format_info *fmt;
> > > +       u32 val, ch_base, hw_fmt;
> > >
> > >         ch_base = sun8i_channel_base(mixer, channel);
> > > +       fmt = state->fb->format;
> > > +       sun8i_mixer_drm_format_to_hw(fmt->format, &hw_fmt);
> > >
> > > -       mask = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_MASK |
> > > -               SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MASK;
> > > -
> > > -       val = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA(plane->state->alpha >> 8);
> > > -
> > > -       val |= (plane->state->alpha == DRM_BLEND_ALPHA_OPAQUE) ?
> > > +       val = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA(state->alpha >> 8);
> > > +       val |= (state->alpha == DRM_BLEND_ALPHA_OPAQUE) ?
> >
> > Changing "plane->state" to "state" made the diff somewhat harder to read.
>
> Do you prefer that I change that in next revision?

No need.