Re: [PATCH v12 2/9] drm/ingenic: Add support for JZ4780 and HDMI output

[Paul Cercueil]

Le mer., févr. 2 2022 at 13:17:14 +0100, H. Nikolaus Schaller 
<hns@xxxxxxxxxxxxx> a écrit :
> Hi Paul,
>
> >  Am 02.02.2022 um 13:06 schrieb Paul Cercueil <paul@xxxxxxxxxxxxxxx>:
> >
> >  Hi Nikolaus,
> >
> > > > >  @@ -446,6 +454,9 @@ static int 
> > > > > ingenic_drm_plane_atomic_check(struct drm_plane *plane,
> > > > >  	if (!crtc)
> > > > >  		return 0;
> > > > >  +	if (plane == &priv->f0)
> > > > >  +		return -EINVAL;
> > > >  This will break JZ4725B -> JZ4770 SoCs, the f0 plane is perfectly 
> > > > usable there.
> > >  Hm. I think it was your request/proposal to add this [1]?
> >
> >  Because otherwise with your current patchset the f0 plane does not 
> > work *on JZ4780*.
>
> Not that I am eager to fix that, but...
> maybe it could be better to fix than having the check and -EINVAL 
> depend on SoC compatible string
> (or some new flag in soc_info. plane_f0_not_working)?

Totally agree! A proper fix would be much better. A 
"plane_f0_not_working" in the meantime is OK with me.

Note that there are other things not working with your current 
implementation, for instance you cannot set the X/Y start position of 
the f1 plane, which means it's only really usable for fullscreen 
desktop/windows.

> >  It does work on older SoCs.
> >
> > >  What I have forgotten is why the f0 plane should not be usable for 
> > > jz4780.
> >
> >  We return an error here to prevent userspace from using the f0 
> > plane until it's effectively working on the JZ4780.
>
> Well, what would be not working with that plane if user-space would 
> try to use it?

From what I remember, it wouldn't show anything on screen, and after 
that trying to use the f1 plane wouldn't work either.

-Paul