From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Ripard Subject: Re: [PATCH 7/15] dt-bindings: display: sun4i: Add allwinner,tcon-channel property Date: Wed, 29 Mar 2017 14:31:18 +0200 Message-ID: <20170329123118.yvwnqpgtamc5pjqf@lukather> References: <20170328100519.145DE203419@relay.mailchannels.net> Reply-To: maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="d6ild6ujpwsam4vj" Return-path: Sender: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org Content-Disposition: inline In-Reply-To: <20170328100519.145DE203419-Y9/x5g2N/Tt0ykcd9G8QkxTxI0vvWBSX@public.gmane.org> List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , To: Icenowy Zheng 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 --d6ild6ujpwsam4vj Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Mar 28, 2017 at 06:05:08PM +0800, Icenowy Zheng wrote: >=20 > 2017=E5=B9=B43=E6=9C=8827=E6=97=A5 =E4=B8=8A=E5=8D=885:11=E4=BA=8E Maxime= Ripard =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, chan= nels.=20 > > > >> When the binding has been introduced, it was assumed that there wo= uld 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 = displays,=20 > > > >> it turns out that the channel 1 can be connected to multiple contr= ollers in=20 > > > >> the SoC (HDMI and TV encoders for example). And while the simultan= eous use=20 > > > >> of HDMI and TV outputs cannot be achieved, switching from one to t= he other=20 > > > >> at runtime definitely sounds plausible.=20 > > > >>=20 > > > >> Add an extra property, allwinner,tcon-channel, to specify for a gi= ven=20 > > > >> endpoint which TCON channel it is connected to, while falling back= to 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 po= rt 0,=20 > > > > endpoint 1 to port 1?=20 > > >=20 > > > Having a separate output port for channel 1 was one option we discuss= ed.=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/R= 8).=20 >=20 > And from A83T on we will face channel-1 only TCONs., which do not > have channel 0 at all in hardware. Yes, but those patches have not been merged yet, so we don't have to care about the backward compatibility. Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com --=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. --d6ild6ujpwsam4vj Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIcBAEBCAAGBQJY26kWAAoJEBx+YmzsjxAgb/MP/jtL0JlIwAveyf/CcfjkxgHw MLNrGlxGFilQgryvyxGYk0QLMYz/1KpXkIWviJHt2dAFkxwxrG/YC6p2zEKDskw0 Pwi0GshgXCs8xRgV98RHH3n60R1tVirmp/S940I1Ci+DdVQVV4Cy/XJzWFqzbpR3 79O2jb+CX5fF/n5g32xij4e5rtjiFRPZ33ywS4J7mRfSf6+aqIx/d51NDncT/3mb dvQp7yp2mijSRe0wjMxaSvAtRWDBl+qqJ7CKfVHhVpm2yONJCIBk1qE1KvFNCT0S c/kX/TIR7hJV2j4HQjkcjSTE3vtX3ZdZxErsnV6Q+8xjnJiT5a65LgsaG09bBEdb IgEL47RcbdYEdObw46n5ykrAyB7IgeQPmhFiftEha28zyVVwjFahEJxBsvj3t57I 93Ll52kx5lw4AB+hEE7e6hbyFaHfMLVXFRuIxjY2/eVKEUOFlm49XfKGey02/lXH l4lwjqAHOO3czlBA/Bh0mLl5mgTrZF9LhjOzYibkqNU6ct+i4aIwmIjN0bQyRUZC UmatmpRh9pliIiBSA3eyKMRkVpY1/6NzVsvwEgvzRuK7MrAFjkQwMjoaFBIazzOI ew5V7qiXXcjJ806QE/dg6PkBVScqUB+14D6/EL9l+HdPzCRAzuG74Dy90wVIPCI8 okHeulGoa3+JdB7BGDPe =8jnb -----END PGP SIGNATURE----- --d6ild6ujpwsam4vj--