2017年3月27日 上午5:11于 Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>写道： > > On Fri, Mar 17, 2017 at 11:34:45AM +0800, Chen-Yu Tsai wrote: > > On Thu, Mar 16, 2017 at 1:37 AM, Rob Herring <robh@xxxxxxxxxx> wrote: > > > On Tue, Mar 07, 2017 at 09:56:26AM +0100, Maxime Ripard wrote: > > >> The Allwinner Timings Controller has two, mutually exclusive, channels. > > >> When the binding has been introduced, it was assumed that there would be > > >> only a single user per channel in the system. > > >> > > >> While this is likely for the channel 0 which only connects to LCD displays, > > >> it turns out that the channel 1 can be connected to multiple controllers in > > >> the SoC (HDMI and TV encoders for example). And while the simultaneous use > > >> of HDMI and TV outputs cannot be achieved, switching from one to the other > > >> at runtime definitely sounds plausible. > > >> > > >> Add an extra property, allwinner,tcon-channel, to specify for a given > > >> endpoint which TCON channel it is connected to, while falling back to the > > >> previous mechanism if that property is missing. > > > > > > I think perhaps TCON channels should have been ports rather than > > > endpoints. The fact that the channels are mutually exclusive can be > > > handled in the driver and doesn't really matter in the binding. How > > > painful would it be to rework things to move TCON channel 1 from port 0, > > > endpoint 1 to port 1? > > > > Having a separate output port for channel 1 was one option we discussed. > > However it wouldn't work well with the kernel's of_graph based crtc > > detection (drm_of_find_possible_crtcs / drm_of_find_possible_crtcs), > > which has the crtcs bound via the output port. As the logic is used > > by multiple drivers, I'm not sure it's easy to rework or test. > > Can't we use a different logic than drm_of_find_possible_crtcs to fill > the same role? > > > Also, we still have to support old device trees using channel 1 from > > output port 0 endpoint 1. This is the TV encoder on sun5i (A10s/A13/R8). And from A83T on we will face channel-1 only TCONs., which do not have channel 0 at all in hardware. > > We could probably work something out if we go that way to deal with > old DTs though. > > Maxime > > -- > Maxime Ripard, Free Electrons > Embedded Linux and Kernel engineering > http://free-electrons.com > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
