On Sun, Jul 1, 2018 at 4:27 PM, Jernej ?krabec [off-list ref] wrote:

Dne ?etrtek, 28. junij 2018 ob 08:24:34 CEST je Chen-Yu Tsai napisal(a):

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On Thu, Jun 28, 2018 at 12:45 PM, Jernej ?krabec

[off-list ref] wrote:

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Dne ?etrtek, 28. junij 2018 ob 03:51:31 CEST je Chen-Yu Tsai napisal(a):

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On Mon, Jun 25, 2018 at 8:02 PM, Jernej Skrabec [off-list ref]

wrote:

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TV TCONs (channel 1 only) are always connected to TV or HDMI encoder.
Because of that, all output endpoints on such TCON node will point to a
encoder which is part of component framework.

Correct current graph traversing algorithm in such way that it doesn't
skip output enpoints with id 0 on TV TCONs.

No. Our bindings say that endpoint 0 _is_ channel 0. For TCONs that don't
have channel 0, it must be skipped.

I'm not sure where this is stated. I read TCON binding again. Can you
please point me to it?

https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bind
ings/display/sunxi/sun4i-drm.txt#L169

Our TCON driver still expects RGB or LVDS panel / bridges on endpoint 0.

Yes, but that can only happen on TCON which has channel 0. TV TCONs (those
with channel 1 only) can't have panels or bridges connected to them, because
they are internally always connected to either HDMI or TV encoder or both.
Actually, R40 is the only SoC, where same TV TCON can be connected to TV
encoder or HDMI. Others have specialized TV TCONs, which are connect to only
one encoder.

IMO TV TCONs are really just stripped down LCD TCONs to support one (or max
two) specific encoder.

I agree. We've seen these first in the H3, and the reverse, TCONs only with
LCD, on the A23/A33.

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So I guess this was sort of implied historically. It's no longer true.
This is something we should probably fix.

Fixed in what way? You mean update bindings to mention that TCON output
endpoint 0 is reserved for panels or bridges?

Either that, or have the drm driver look at other endpoints. I guess we
should ask Maxime if this is already done or not, since the DSI driver
isn't endpoint 0 in the A33 dtsi.

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In practice our drivers don't look at it (yet), but rely on the downstream
encoder type to determine which channel to use.

But please add the "allwinner,tcon-channel" property as specified in
the binding.

It's my understanding of TCON binding documentation that property
"allwinner,tcon-channel" is needed only if TCON supports both channels. TV
TCON clearly supports only channel 1. In that case, there is no doubt to which
channel output endpoint belongs.

If that's not true, dt bindings documentation should be reworded to contain
word "needed" or something similar. Currently, no DT for newer SoC contains
that property (for example, A83T, H3, H5 or even A33). On A33 this is even
more interesting, since tcon0 has only channel 0 and has DSI output endpoint
with number 1. According to TCON binding docs, if "allwinner,tcon-channel" is
not preset, endpoint number represent channel. So, that would mean DSI needs
channel 1 on tcon which supports clearly only channel 0. So either there TCON
bindings documentation needs updates or DT for A33 has to be updated.

Maxime? You did the A33 DSI stuff.

BTW, "allwinner,tcon-channel" property is not used at all in the code.

Yes I'm aware. We just base the channel selection on the encoder type instead.
TV-like ones use channel 1, LCD ones use channel 0.

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So on TV TCONs on R40 (without channel 0) TVE would be endpoint 1 and HDMI
endpoint 2 (or the other way around)?

Which one goes first doesn't quite matter. IIRC there's also a mux for TVE?

AFAIK, TV TCON is by default connected to TV encoder unless HDMI mux in TCON
TOP points to it. I think it's best put TVE with lower number since it's
default and HDMI with higher number.

Ok. As long as its specified in the binding, as a contract between the dts
and the graph parsing code.

Regards
ChenYu