On Thu, Jul 05, 2018 at 10:03:35PM +0200, Jernej Škrabec wrote: > Dne četrtek, 05. julij 2018 ob 09:03:58 CEST je Maxime Ripard napisal(a): > > On Sun, Jul 01, 2018 at 11:11:06PM +0800, Chen-Yu Tsai wrote: > > > On Sun, Jul 1, 2018 at 4:27 PM, Jernej Škrabec <jernej.skrabec@xxxxxxxx> > wrote: > > > > Dne četrtek, 28. junij 2018 ob 08:24:34 CEST je Chen-Yu Tsai napisal(a): > > > >> On Thu, Jun 28, 2018 at 12:45 PM, Jernej Škrabec > > > >> > > > >> <jernej.skrabec@xxxxxxxx> wrote: > > > >> > Dne četrtek, 28. junij 2018 ob 03:51:31 CEST je Chen-Yu Tsai > napisal(a): > > > >> >> On Mon, Jun 25, 2018 at 8:02 PM, Jernej Skrabec > > > >> >> <jernej.skrabec@xxxxxxxx> > > > >> > > > > >> > wrote: > > > >> >> > 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. > > > > > > >> 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. > > > > The DSI driver isn't really a good example for this, since the panel > > isn't described as part of the OF graph, but DSI binding require that > > it's a child of the DSI controller node. > > So should be new behaviour reverted? I mean ignoring endpoint 0 on TV TCONs. > > For me, it doesn't make sense to check for panel or bridges on TV TCONs, > because they are never exposed on physical pins. They are always connected to > TVE or HDMI encoder internally. It doesn't make sense to check for panels, yes, but it also makes sens to have a child node at the endpoint 0 for TV TCONs. > > > >> 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). > > > > Yeah, but that's mainly because we have a single output enabled for > > each channel on those newer SoCs. When / if we enable the RGB and LVDS > > output for example, we will have to set this. > > So just to be clear, before I send follow up series, I have to add > "allwinner,tcon-channel" property to DT, because both TV TCONs can be > connected to either TVE or HDMI (trough TCON TOP)? > > BTW, since this property is not used at all in the code, why not just simply > deprecate it and remove it from existing DTs? I noticed this is standard > practice for obsolete properties. It's not deprecated or obsolete, it's future-proofing. Maxime -- Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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