Hi, On Fri, Nov 18, 2016 at 10:22:40AM +0800, Chen-Yu Tsai wrote: > On Fri, Nov 18, 2016 at 3:02 AM, Maxime Ripard > <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: > > On Wed, Nov 16, 2016 at 05:37:31PM +0800, Chen-Yu Tsai wrote: > >> The sun4i DRM driver counts the number of endpoints it found and > >> registers the whole DRM pipeline if any endpoints are found. > >> > >> However, if the TCON and its child endpoints (LCD panels, TV encoder, > >> HDMI encoder, MIPI DSI encoder, etc.) aren't found, that means we > >> don't have any usable CRTCs, and the display pipeline is incomplete > >> and useless. > > > > If some node set as available is not probed, then yes, it does, but > > I'm not really sure how it's a problem. Quite the opposite actually. > > Actually the problem occurs when the TCON is _not_ available, but > the other endpoints preceding it are. By preceding, you mean the display engine or the HDMI or TV encoders? > >> The debug message "Queued %d outputs on pipeline %d\n" is also telling. > >> > >> This patch makes the driver only count enabled TCON endpoints. If > >> none are found, the DRM pipeline is not used. This avoids screwing > >> up the simple framebuffer provided by the bootloader in cases where > >> we aren't able to support the display with the DRM subsystem, due > >> to lack of panel or bridge drivers, or just lack of progress. > > > > The framebuffer is removed only at bind time, which means that all the > > drivers have probed already. Lack of progress isn't an issue here, > > since the node simply won't be there, and we wouldn't have it in the > > component lists. And lack of drivers shouldn't be an issue either, > > since in order for bind to be called, all the drivers would have > > gone through their probe. > > > > So I'm not really sure what it fixes. > > To recap, on sun6i I had enabled the display engine node by default > in the dtsi, along with the backend and drc. The tcon is disabled > by default, so it doesn't get added to the list of components. > The available components get probed, binded, and simplefb gets > pushed out. > > I suppose disabling the display engine by default would be better? > At least simplefb still works. Yep, that works for me. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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