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From:   Jernej =?utf-8?B?xaBrcmFiZWM=?= <jernej.skrabec@siol.net>
To:     Roman Stratiienko <roman.stratiienko@globallogic.com>
Cc:     mripard@kernel.org, linux-kernel@vger.kernel.org,
        dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/sun4i: Use vi plane as primary
Date:   Thu, 19 Sep 2019 23:09:22 +0200
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Dne četrtek, 19. september 2019 ob 22:03:26 CEST je Roman Stratiienko 
napisal(a):
> Hello guys,
> 
> Actually, I beleive this is True solution, and current one is wrong.  Let
> me explain why.
> 
> De2. 0 was designed to match Android hwcomposer hal requirements IMO.
> You can easily agree with this conclusion by comparing Composer HAL and
> De2. 0 hardware manuals.
> 
> I faced at least 4 issues when try to run Android using the mainline kernel
> sun8i mixer implementation. Current one, missing pixel formats (my previous
> patch), missing plane alpha and rotation properties. I plan to fix it and
> also send appropriate solution to the upstream.

Android and mainline Linux don't have necessarily same view how things should 
work. Check how different Android version of Linux kernel was in the past. 
Fortunately, they are converging now. 

While I agree that HW was probably designed with Android in mind, that doesn't 
mean that Android way is the best or only way of doing things. Android can 
afford a lot of non-intuitive things because it's closed system and all IP 
cores are used only in certain ways. You can't say that for general Linux 
distro.

Would you say that advertising formats with alpha support is correct thing to 
do if alpha blending is not supported? Put aside the fact that it makes it 
easier to implement Android features for you and imagine some app which finds 
first available overlay plane with ARGB8888 support. It puts it on top with 
zpos property and gives it some transparent image. If that plane is VI, it 
would look wrong and users would complain. At the end, it's not apps fault to 
expect that if plane advertises format with alpha channel actually supports 
transparency.

Regarding rotation, that core is not part of display pipeline. It takes one 
buffer and writes transformed (rotated in this case) image to output buffer. 
This principle is very definition of V4L2 M2M framework and should be handled 
by it.

> 
> To achieve optimal UI performance Android requires at least 4 ui layers to
> make screen composition. Current patch enables 4th plane usable.

Ah, your idea is to pretend that VI planes supports all features of UI planes 
while in fact they not?

> 
> As for using vi plane to display video. I assume that some of current users
> may have regression in their software, but it could be easily fixed. For
> example if vi layer isn't fullscreen and should be on top of the other
> layers, it can actually be placed on the bottom and overlayed with pictures
> with transparent rectangles in video region.

This idea is imposible to implement if VI plane becomes primary plane. Apps 
wouldn't find overlay plane which suports YUV buffers and only one which does, 
it's already taken by window manager for rendering windows.

Best regards,
Jernej

> But I assume most of users such as browser etc. uses GPU for that.
> 
> And if you are watching fullscreen video, I can imagine only subtitles
> layer and advertizing layers on top of the video layers.
> 
> чт, 19 сент. 2019 г., 21:15 Jernej Škrabec <jernej.skrabec@siol.net>:
> > Dne četrtek, 19. september 2019 ob 19:17:54 CEST je Maxime Ripard
> > 
> > napisal(a):
> > > Hi,
> > > 
> > > On Thu, Sep 19, 2019 at 03:37:03PM +0300,
> > 
> > roman.stratiienko@globallogic.com
> > 
> > wrote:
> > > > From: Roman Stratiienko <roman.stratiienko@globallogic.com>
> > > > 
> > > > DE2.0 blender does not take into the account alpha channel of vi
> > > > layer.
> > > > Thus makes overlaying of this layer totally opaque.
> > > > Using vi layer as bottom solves this issue.
> > 
> > What issue? Overlays don't have to be "full screen", thus missing support
> > for
> > alpha blending doesn't make it less valuable. And VI planes are already
> > placed
> > at the bottom (zpos = 0).
> > 
> > > > Tested on Android.
> > > > 
> > > > Signed-off-by: Roman Stratiienko <roman.stratiienko@globallogic.com>
> > > 
> > > It sounds like a workaround more than an actual fix.
> > > 
> > > If the VI planes can't use the alpha, then we should just stop
> > > reporting that format.
> > > 
> > > Jernej, what do you think?
> > 
> > Commit message is misleading. What this commit actually does is moving
> > primary
> > plane from first UI plane to bottom most plane, i.e. first VI plane.
> > However, VI
> > planes are scarce resource, almost all mixers have only one. I wouldn't
> > set it
> > as primary, because it's the only one which provide support for YUV
> > formats.
> > That could be used for example by video player for zero-copy rendering.
> > Probably most apps wouldn't touch it if it was primary (that's usually
> > reserved for window manager, if used).
> > 
> > I left few formats with alpha channel exposed by VI planes, just because
> > they
> > don't have equivalent format without alpha. But I'm fine with removing
> > them if
> > you all agree on that.
> > 
> > Best regards,
> > Jernej
> > 
> > > Maxime
> > > 
> > > > ---
> > > > 
> > > >  drivers/gpu/drm/sun4i/sun8i_ui_layer.c | 33 -----------------------
> > > >  drivers/gpu/drm/sun4i/sun8i_vi_layer.c | 36
> > > >  +++++++++++++++++++++++++-
> > > >  2 files changed, 35 insertions(+), 34 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
> > > > b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c index
> > 
> > dd2a1c851939..25183badc85f
> > 
> > > > 100644
> > > > --- a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
> > > > +++ b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
> > > > @@ -99,36 +99,6 @@ static int sun8i_ui_layer_update_coord(struct
> > > > sun8i_mixer *mixer, int channel,>
> > > > 
> > > >     insize = SUN8I_MIXER_SIZE(src_w, src_h);
> > > >     outsize = SUN8I_MIXER_SIZE(dst_w, dst_h);
> > > > 
> > > > -   if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
> > > > -           bool interlaced = false;
> > > > -           u32 val;
> > > > -
> > > > -           DRM_DEBUG_DRIVER("Primary layer, updating global size
> > 
> > W: %u H: %u\n",
> > 
> > > > -                            dst_w, dst_h);
> > > > -           regmap_write(mixer->engine.regs,
> > > > -                        SUN8I_MIXER_GLOBAL_SIZE,
> > > > -                        outsize);
> > > > -           regmap_write(mixer->engine.regs,
> > > > -                        SUN8I_MIXER_BLEND_OUTSIZE(bld_base),
> > 
> > outsize);
> > 
> > > > -
> > > > -           if (state->crtc)
> > > > -                   interlaced = state->crtc->state-
> > >
> > >adjusted_mode.flags
> > >
> > > > -                           & DRM_MODE_FLAG_INTERLACE;
> > > > -
> > > > -           if (interlaced)
> > > > -                   val = SUN8I_MIXER_BLEND_OUTCTL_INTERLACED;
> > > > -           else
> > > > -                   val = 0;
> > > > -
> > > > -           regmap_update_bits(mixer->engine.regs,
> > > > -
> > 
> > SUN8I_MIXER_BLEND_OUTCTL(bld_base),
> > 
> > > > -
> > 
> > SUN8I_MIXER_BLEND_OUTCTL_INTERLACED,
> > 
> > > > -                              val);
> > > > -
> > > > -           DRM_DEBUG_DRIVER("Switching display mixer interlaced
> > 
> > mode %s\n",
> > 
> > > > -                            interlaced ? "on" : "off");
> > > > -   }
> > > > -
> > > > 
> > > >     /* Set height and width */
> > > >     DRM_DEBUG_DRIVER("Layer source offset X: %d Y: %d\n",
> > > >     
> > > >                      state->src.x1 >> 16, state->src.y1 >> 16);
> > > > 
> > > > @@ -349,9 +319,6 @@ struct sun8i_ui_layer
> > 
> > *sun8i_ui_layer_init_one(struct
> > 
> > > > drm_device *drm,>
> > > > 
> > > >     if (!layer)
> > > >     
> > > >             return ERR_PTR(-ENOMEM);
> > > > 
> > > > -   if (index == 0)
> > > > -           type = DRM_PLANE_TYPE_PRIMARY;
> > > > -
> > > > 
> > > >     /* possible crtcs are set later */
> > > >     ret = drm_universal_plane_init(drm, &layer->plane, 0,
> > > >     
> > > >                                    &sun8i_ui_layer_funcs,
> > > > 
> > > > diff --git a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
> > > > b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c index
> > 
> > 07c27e6a4b77..49c4074e164f
> > 
> > > > 100644
> > > > --- a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
> > > > +++ b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
> > > > @@ -116,6 +116,36 @@ static int sun8i_vi_layer_update_coord(struct
> > > > sun8i_mixer *mixer, int channel,>
> > > > 
> > > >     insize = SUN8I_MIXER_SIZE(src_w, src_h);
> > > >     outsize = SUN8I_MIXER_SIZE(dst_w, dst_h);
> > > > 
> > > > +   if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
> > > > +           bool interlaced = false;
> > > > +           u32 val;
> > > > +
> > > > +           DRM_DEBUG_DRIVER("Primary layer, updating global size
> > 
> > W: %u H: %u\n",
> > 
> > > > +                            dst_w, dst_h);
> > > > +           regmap_write(mixer->engine.regs,
> > > > +                        SUN8I_MIXER_GLOBAL_SIZE,
> > > > +                        outsize);
> > > > +           regmap_write(mixer->engine.regs,
> > > > +                        SUN8I_MIXER_BLEND_OUTSIZE(bld_base),
> > 
> > outsize);
> > 
> > > > +
> > > > +           if (state->crtc)
> > > > +                   interlaced = state->crtc->state-
> > >
> > >adjusted_mode.flags
> > >
> > > > +                           & DRM_MODE_FLAG_INTERLACE;
> > > > +
> > > > +           if (interlaced)
> > > > +                   val = SUN8I_MIXER_BLEND_OUTCTL_INTERLACED;
> > > > +           else
> > > > +                   val = 0;
> > > > +
> > > > +           regmap_update_bits(mixer->engine.regs,
> > > > +
> > 
> > SUN8I_MIXER_BLEND_OUTCTL(bld_base),
> > 
> > > > +
> > 
> > SUN8I_MIXER_BLEND_OUTCTL_INTERLACED,
> > 
> > > > +                              val);
> > > > +
> > > > +           DRM_DEBUG_DRIVER("Switching display mixer interlaced
> > 
> > mode %s\n",
> > 
> > > > +                            interlaced ? "on" : "off");
> > > > +   }
> > > > +
> > > > 
> > > >     /* Set height and width */
> > > >     DRM_DEBUG_DRIVER("Layer source offset X: %d Y: %d\n",
> > > >     
> > > >                      (state->src.x1 >> 16) & ~(format->hsub -
> > 
> > 1),
> > 
> > > > @@ -445,6 +475,7 @@ struct sun8i_vi_layer
> > 
> > *sun8i_vi_layer_init_one(struct
> > 
> > > > drm_device *drm,>
> > > > 
> > > >                                            struct
> > 
> > sun8i_mixer *mixer,
> > 
> > > >                                            int index)
> > > >  
> > > >  {
> > > > 
> > > > +   enum drm_plane_type type = DRM_PLANE_TYPE_OVERLAY;
> > > > 
> > > >     struct sun8i_vi_layer *layer;
> > > >     unsigned int plane_cnt;
> > > >     int ret;
> > > > 
> > > > @@ -453,12 +484,15 @@ struct sun8i_vi_layer
> > > > *sun8i_vi_layer_init_one(struct drm_device *drm,>
> > > > 
> > > >     if (!layer)
> > > >     
> > > >             return ERR_PTR(-ENOMEM);
> > > > 
> > > > +   if (index == 0)
> > > > +           type = DRM_PLANE_TYPE_PRIMARY;
> > > > +
> > > > 
> > > >     /* possible crtcs are set later */
> > > >     ret = drm_universal_plane_init(drm, &layer->plane, 0,
> > > >     
> > > >                                    &sun8i_vi_layer_funcs,
> > > >                                    sun8i_vi_layer_formats,
> > 
> > ARRAY_SIZE(sun8i_vi_layer_formats),
> > 
> > > > -                                  NULL,
> > 
> > DRM_PLANE_TYPE_OVERLAY, NULL);
> > 
> > > > +                                  NULL, type, NULL);
> > > > 
> > > >     if (ret) {
> > > >     
> > > >             dev_err(drm->dev, "Couldn't initialize layer\n");
> > > >             return ERR_PTR(ret);
> > > > 
> > > > --
> > > > 2.17.1