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. > >> > >> 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. > > 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. I guess it's missing on the A33 DSI endpoint. Maxime -- Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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