From mboxrd@z Thu Jan 1 00:00:00 1970 From: Icenowy Zheng Subject: Re: [PATCH 7/15] dt-bindings: display: sun4i: Add allwinner,tcon-channel property Date: Tue, 28 Mar 2017 18:05:08 +0800 Message-ID: <58da355e.0219620a.618f7.6caeSMTPIN_ADDED_MISSING@gmr-mx.google.com> Reply-To: icenowy-h8G6r0blFSE@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Return-path: Sender: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , To: Maxime Ripard Cc: linux-arm-kernel , Mike Turquette , David Airlie , Mark Rutland , Daniel Vetter , linux-sunxi , linux-kernel , Stephen Boyd , devicetree , linux-clk , dri-devel , Chen-Yu Tsai , Rob Herring List-Id: devicetree@vger.kernel.org 2017=E5=B9=B43=E6=9C=8827=E6=97=A5 =E4=B8=8A=E5=8D=885:11=E4=BA=8E Maxime R= ipard =E5=86=99=E9=81=93=EF=BC=9A > > On Fri, Mar 17, 2017 at 11:34:45AM +0800, Chen-Yu Tsai wrote:=20 > > On Thu, Mar 16, 2017 at 1:37 AM, Rob Herring wrote:= =20 > > > On Tue, Mar 07, 2017 at 09:56:26AM +0100, Maxime Ripard wrote:=20 > > >> The Allwinner Timings Controller has two, mutually exclusive, channe= ls.=20 > > >> When the binding has been introduced, it was assumed that there woul= d be=20 > > >> only a single user per channel in the system.=20 > > >>=20 > > >> While this is likely for the channel 0 which only connects to LCD di= splays,=20 > > >> it turns out that the channel 1 can be connected to multiple control= lers in=20 > > >> the SoC (HDMI and TV encoders for example). And while the simultaneo= us use=20 > > >> of HDMI and TV outputs cannot be achieved, switching from one to the= other=20 > > >> at runtime definitely sounds plausible.=20 > > >>=20 > > >> Add an extra property, allwinner,tcon-channel, to specify for a give= n=20 > > >> endpoint which TCON channel it is connected to, while falling back t= o the=20 > > >> previous mechanism if that property is missing.=20 > > >=20 > > > I think perhaps TCON channels should have been ports rather than=20 > > > endpoints. The fact that the channels are mutually exclusive can be= =20 > > > handled in the driver and doesn't really matter in the binding. How= =20 > > > painful would it be to rework things to move TCON channel 1 from port= 0,=20 > > > endpoint 1 to port 1?=20 > >=20 > > Having a separate output port for channel 1 was one option we discussed= .=20 > > However it wouldn't work well with the kernel's of_graph based crtc=20 > > detection (drm_of_find_possible_crtcs / drm_of_find_possible_crtcs),=20 > > which has the crtcs bound via the output port. As the logic is used=20 > > by multiple drivers, I'm not sure it's easy to rework or test.=20 > > Can't we use a different logic than drm_of_find_possible_crtcs to fill=20 > the same role?=20 > > > Also, we still have to support old device trees using channel 1 from=20 > > output port 0 endpoint 1. This is the TV encoder on sun5i (A10s/A13/R8)= .=20 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=20 > old DTs though.=20 > > Maxime=20 > > --=20 > Maxime Ripard, Free Electrons=20 > Embedded Linux and Kernel engineering=20 > http://free-electrons.com > > _______________________________________________=20 > linux-arm-kernel mailing list=20 > linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org=20 > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel=20 --=20 You received this message because you are subscribed to the Google Groups "= linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to linux-sunxi+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit https://groups.google.com/d/optout.