Re: [linux-sunxi] Re: [RFC PATCH] ARM: dts: sun8i: add simplefb node for H3

[Jean-Francois Moine <moinejf@free.fr>]

On Wed, 30 Nov 2016 20:14:11 +0100
Jernej Škrabec <jernej.skrabec@gmail.com> wrote:

> Dne četrtek, 01. december 2016 ob 03:03:14 CET je Icenowy Zheng napisal(a):
> > 2016年12月1日 02:49于 Jernej Skrabec <jernej.skrabec@gmail.com>写道：
> > 
> > > Hi Jean-François,
> > > 
> > > Dne sreda, 30. november 2016 10.35.08 UTC+1 je oseba Jean-François Moine 
> napisala:
> > >> On Tue, 29 Nov 2016 22:59:32 +0100
> > >> 
> > >> Maxime Ripard <maxime...@free-electrons.com> wrote:
> > >> > > > I'm still not sure which pipeline should I use.
> > >> > > > 
> > >> > > > And, it seems that HDMI Slow Clock is not needed?
> > >> > > > 
> > >> > > > (seems that it's only for EDID, but simplefb won't use EDID)
> > >> > > 
> > >> > > So, I don't see how this may work.
> > >> > > How can the u-boot know the resolutions of the HDMI display device?
> > >> > > 
> > >> > > In other words: I have a new H3 board with the last u-boot and
> > >> > > kernel.
> > >> > > I plug my (rather old or brand new) HDMI display device.
> > >> > > After powering on the system, I hope to get something on the screen.
> > >> > > How?
> > >> > 
> > >> > If it works like the driver for the first display engine in U-Boot, it
> > >> > will use the preferred mode reported by the EDID, and will fallback to
> > >> > 1024x768 if it cannot access it.
> > >> 
> > >> Icenowy wrote: "simplefb won't use EDID"
> > >> 
> > >> Then, if it is like in the kernel, the 1024x768 mode is VGA. It does
> > >> not work with HDMI (different timings).
> > > 
> > > U-Boot driver now accept any timings recommended by EDID. So far it
> > > was tested with at least following resolutions:
> > > - 1920x1080 @ 60 Hz
> > > - 1280x1024 @ 60 Hz
> > > - 1280x800 @ 60 Hz (slight clock difference)
> > > - 800x480 (not sure about frame rate)
> > > - 3840x2160 @ 30 Hz (4K)
> > 
> > I tested on 1024x600 (If my memory is right, it's @ 60Hz)
> > 
> > > and nobody complained so far. I'm pretty sure 1024x768 would work.

Check the timings offered by the DRM core.

> > > 
> > >> > Maybe it would be worth exchanging on the EDID code that has been done
> > >> > for the u-boot driver too, so that it can be fixed in your driver.
> > >> 
> > >> The u-boot got my code, and, up to now, I could not fix the random or
> > >> permanent failures of EDID reading in some boards.
> > > 
> > > I only have one OPi2, but as I said, EDID always worked for me.

Happy guy!

> > > The only
> > > code left from you is for DE2. HDMI stuff is basically copied from Rockhip
> > > driver (including EDID reading), TCON code is now reverted to the same as
> > > it is in sunxi_display.c. I think it is worth to take a look at EDID code
> > > and compare it.
> > 
> > So is the TCON of DE 2.0 identical to the original TCON?
> > 
> > If so, we should reuse sun4i-tcon ...
> 
> Well, TCON is splitted in two parts (two base addresses), one for HDMI and one 
> for TV. However, register offsets are same as before, so I guess driver 
> reusage make sense. I think that there are few additional registers, but they 
> can be ignored for simplefb.

The TCON1 of the H3 is not usable (no ckock). Analog TV has its own
clock and I/O area.

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