[PATCH v7 0/8] drm: sun8i: Add DE2 HDMI video support

[Jernej Skrabec]

Hi Laurent,

Dne sreda, 30. november 2016 09.08.22 UTC+1 je oseba Laurent Pinchart 
napisala:
>
> Hi Jernej, 
>
> On Tuesday 29 Nov 2016 15:24:25 Jernej Skrabec wrote: 
> > Dne torek, 29. november 2016 23.56.31 UTC+1 je oseba Laurent Pinchart 
> > napisala: 
> > > On Tuesday 29 Nov 2016 14:47:20 Jernej Skrabec wrote: 
> > >> Dne torek, 29. november 2016 22.37.03 UTC+1 je oseba Maxime Ripard 
> > > napisala: 
> > >>> On Tue, Nov 29, 2016 at 11:18:35AM +0100, Jean-Francois Moine wrote: 
> > >>>> This patchset series adds HDMI video support to the Allwinner 
> > >>>> sun8i SoCs which include the display engine 2 (DE2). 
> > >>>> The driver contains the code for the A83T and H3 SoCs, and 
> > >>>> some H3 boards, but it could be used/extended for other SoCs 
> > >>>> (A64, H2, H5) and boards (Banana PIs, Orange PIs). 
> > >>> 
> > >>> Honestly, I'm getting a bit worried by the fact that you ignore 
> > >>> reviews. 
> > >>> 
> > >>> On the important reviews that you got that are to be seen as major 
> > >>> issues that block the inclusion, we have: 
> > >>>   - The fact that the HDMI driver is actually just a designware IP, 
> > >>>     and while you should use the driver that already exists, you 
> just 
> > >>>     duplicated all that code. 
> > >> 
> > >> That might be hard thing to do. A83T fits perfectly, but H3 and newer 
> > >> SoCs do not. They are using completely different HDMI phy. Decoupling 
> > >> controller and phy code means rewritting a good portion of the code, 
> > >> unless some tricks are applied, like calling phy function pointers, 
> if 
> > >> they are defined. 
> > > 
> > > Same HDMI TX but different HDMI TX PHY ? Kieran is working on 
> decoupling 
> > > the PHY configuration code for a Renesas SoC, that might be of 
> interest to 
> > > you. 
> > 
> > Exactly. I'm developing only U-Boot driver, but Jean-Francois will 
> probably 
> > have more interest in this. 
>
> We'll post patches as soon as they're ready. 
>

Great. Is datasheet public? I'm curious if HDMI PHY is by any chance 
similar.
 

>
> By the way, do you know if the H3 and newer SoCs use a different PHY from 
> Synopsys, or a custom PHY developed by Allwinner ? 
>
>
Unfortunatelly, noone managed to identify PHY and Alliwinner never released 
a
bit of information about HDMI. Does config2_id code 0xFE (PHY type) tell you
anything?
 

> > >> Register addresses also differ, but that can be easily solved by 
> using 
> > >> undocumented magic value to restore them. 
> > > 
> > > I love that :-) 
> > 
> > Is it allowed to use magic number which was found in binary blob? I'm 
> new in 
> > all this. 
>
> I don't really see a problem with that, we have many drivers in the kernel 
> that have been developed through reverse-engineering. You should not 
> include 
> large pieces of code that have been obtained through decompilation of a 
> proprietary binary blob as those could be protected by copyright, but 
> writing 
> to undocumented registers based on information found through usage of a 
> binary 
> driver isn't a problem. (Please remember that I'm not a lawyer though) 
>
> > >>>   - The fact that you ignored Rob (v6) and I (v5) comment on using 
> OF 
> > >>>     graph to model the connection between the display engine and the 
> > >>>     TCON. Something that Laurent also pointed out in this version. 
> > >>>   
> > >>>   - The fact that you ignored that you needed an HDMI connector node 
> > >>>     as a child of the HDMI controller. This has been reported by Rob 
> > >>>     (v6) and yet again in this version by Laurent. 
> > >>>   
> > >>>   - And finally the fact that we can't have several display engine 
> in 
> > >>>     parallel, if needs be. This has happened in the past already on 
> > >>>     Allwinner SoCs, so it's definitely something we should consider 
> in 
> > >>>     the DT bindings, since we can't break them. 
> > >>> 
> > >>> Until those are fixed, I cannot see how this driver can be merged, 
> > >>> unfortunately. 
>

Best regards,
Jernej Škrabec
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