From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jernej =?utf-8?B?xaBrcmFiZWM=?= Subject: Re: Re: [PATCH v3 09/24] drm/sun4i: Don't skip TCONs if they don't have channel 0 Date: Sun, 01 Jul 2018 10:27:43 +0200 Message-ID: <8952939.l1hLr1Mv9y@jernej-laptop> References: <20180625120304.7543-1-jernej.skrabec@siol.net> <2676604.ZYCNkuCdbT@jernej-laptop> Reply-To: jernej.skrabec-gGgVlfcn5nU@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 In-Reply-To: List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , To: Chen-Yu Tsai Cc: Maxime Ripard , Rob Herring , David Airlie , Gustavo Padovan , Maarten Lankhorst , Sean Paul , Mark Rutland , dri-devel , devicetree , linux-arm-kernel , linux-kernel , linux-clk , linux-sunxi List-Id: devicetree@vger.kernel.org Dne =C4=8Detrtek, 28. junij 2018 ob 08:24:34 CEST je Chen-Yu Tsai napisal(a= ): > On Thu, Jun 28, 2018 at 12:45 PM, Jernej =C5=A0krabec >=20 > wrote: > > Dne =C4=8Detrtek, 28. junij 2018 ob 03:51:31 CEST je Chen-Yu Tsai napis= al(a): > >> On Mon, Jun 25, 2018 at 8:02 PM, Jernej Skrabec > >=20 > > 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 t= o a > >> > encoder which is part of component framework. > >> >=20 > >> > Correct current graph traversing algorithm in such way that it doesn= 't > >> > skip output enpoints with id 0 on TV TCONs. > >>=20 > >> No. Our bindings say that endpoint 0 _is_ channel 0. For TCONs that do= n't > >> have channel 0, it must be skipped. > >=20 > > I'm not sure where this is stated. I read TCON binding again. Can you > > please point me to it? >=20 > https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/b= ind > ings/display/sunxi/sun4i-drm.txt#L169 >=20 > 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= =20 with channel 1 only) can't have panels or bridges connected to them, becaus= e=20 they are internally always connected to either HDMI or TV encoder or both.= =20 Actually, R40 is the only SoC, where same TV TCON can be connected to TV=20 encoder or HDMI. Others have specialized TV TCONs, which are connect to onl= y=20 one encoder. IMO TV TCONs are really just stripped down LCD TCONs to support one (or max= =20 two) specific encoder. > 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=20 endpoint 0 is reserved for panels or bridges? >=20 > In practice our drivers don't look at it (yet), but rely on the downstrea= m > encoder type to determine which channel to use. >=20 > But please add the "allwinner,tcon-channel" property as specified in > the binding. It's my understanding of TCON binding documentation that property=20 "allwinner,tcon-channel" is needed only if TCON supports both channels. TV= =20 TCON clearly supports only channel 1. In that case, there is no doubt to wh= ich=20 channel output endpoint belongs. If that's not true, dt bindings documentation should be reworded to contain= =20 word "needed" or something similar. Currently, no DT for newer SoC contains= =20 that property (for example, A83T, H3, H5 or even A33). On A33 this is even= =20 more interesting, since tcon0 has only channel 0 and has DSI output endpoin= t=20 with number 1. According to TCON binding docs, if "allwinner,tcon-channel" = is=20 not preset, endpoint number represent channel. So, that would mean DSI need= s=20 channel 1 on tcon which supports clearly only channel 0. So either there TC= ON=20 bindings documentation needs updates or DT for A33 has to be updated. BTW, "allwinner,tcon-channel" property is not used at all in the code. >=20 > > So on TV TCONs on R40 (without channel 0) TVE would be endpoint 1 and H= DMI > > endpoint 2 (or the other way around)? >=20 > Which one goes first doesn't quite matter. IIRC there's also a mux for TV= E? AFAIK, TV TCON is by default connected to TV encoder unless HDMI mux in TCO= N=20 TOP points to it. I think it's best put TVE with lower number since it's=20 default and HDMI with higher number. Best regards, Jernej --=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.