Daniel Vetter <daniel@xxxxxxxx> writes: > On Mon, Nov 20, 2017 at 08:53:05AM +0100, Andrzej Hajda wrote: >> On 18.11.2017 02:16, Eric Anholt wrote: >> > Andrzej Hajda <a.hajda@xxxxxxxxxxx> writes: >> > >> >> On 16.11.2017 21:27, Eric Anholt wrote: >> >>> Andrzej Hajda <a.hajda@xxxxxxxxxxx> writes: >> >>> >> >>>> On 15.11.2017 21:26, Eric Anholt wrote: >> >>>>> I'm happy to have the DSI panel finally working on VC4 (just waiting on >> >>>>> https://lists.freedesktop.org/archives/dri-devel/2017-October/156407.html), >> >>>>> but now I've got another problem to solve. It would be great if I could >> >>>>> include the DSI panel in our upstream DT, so that it automatically >> >>>>> worked when you plugged one in. However, right now we return >> >>>>> -EPROBE_DEFER during bind unless the panel has actually shown up. This >> >>>>> means that if you don't have the panel actually connected, you get this >> >>>>> sequence at startup: >> >>>>> >> >>>>> [ 10.719929] [drm] Initialized >> >>>>> [ 10.829510] vc4_hdmi 3f902000.hdmi: vc4-hdmi-hifi <-> 3f902000.hdmi mapping ok >> >>>>> [ 10.844043] vc4-drm soc:gpu: bound 3f902000.hdmi (ops vc4_hdmi_ops [vc4]) >> >>>>> [ 10.848626] vc4-drm soc:gpu: bound 3f806000.vec (ops vc4_vec_ops [vc4]) >> >>>>> [ 10.850214] vc4-drm soc:gpu: failed to bind 3f700000.dsi (ops vc4_dsi_ops [vc4]): -517 >> >>>>> [ 10.856559] vc4-drm soc:gpu: master bind failed: -517 >> >>>>> >> >>>>> [...] >> >>>>> >> >>>>> [ 10.967718] rpi_touchscreen 3-0045: Atmel I2C read failed: -6 >> >>>>> >> >>>>> Once the panel driver fails to probe, we never get asked to re-bind vc4, >> >>>>> and drm_of_find_panel_or_bridge looks like it would just give us >> >>>>> -EPROBE_DEFER again since the panel still wasn't registered. >> >>>>> >> >>>>> Does anyone have any suggestions for handling this? >> >>>> I guess you should call component_add only when all required resources >> >>>> are present(including panel), I suppose moving it to vc4_dsi_host_attach >> >>>> should help. >> >>> How can I decide when the panel driver has tried to probe and failed, >> >>> versus not tried to probe yet? find_panel_or_bridge gives me >> >>> -EPROBE_DEFER either way. >> >>> >> >>>> On the other side I am curious why EPROBE_DEFER from bind does not fail >> >>>> probing of some component (the last one probed), with proper error >> >>>> propagation it should cause defer_probing of one of the components or >> >>>> master, and probe/bind should be retried after panel's probe. >> >>> The panel probe failed, though, so there's no trigger to re-probe other >> >>> drivers. >> >> OK, I misunderstood your problem. And after 2nd read I am not sure what >> >> do you want to achieve exactly? >> >> >> >> Do you want to 'hotplug' DSI panel? Or just make it working with and >> >> without the panel. In 2nd case other paths (HDMI) should still work, I >> >> guess. >> > Yeah, the second thing. I would like to use a single DT to describe a >> > platform where the panel may or may not be present, so the panel driver >> > (panel-raspberrypi-touchscreen.c) will throw an error from the I2C part >> > of the probe or not instead of creating the DSI device and attaching the >> > panel. >> > >> >> Lets assume that you are interested in the latter case. There could be >> >> multiple solutions more or less hacky: >> >> >> >> 1. Use connector's HPD infrastructure to signal presence of the panel, >> >> ie. in mipi_dsi::host_(attach|detach) callback you grab the panel and >> >> change connector status to connected|disconnected and calls >> >> drm_kms_helper_hotplug_event, it is done this way in exynos_dsi_host_attach. >> > This is basically what I had before all the review reworks, and the >> > regression from this state is keeping me from merging the current driver >> > downstream. >> > >> > This option is unfortunate because we'll have forced *some* output on at >> > boot time, and then when the panel driver shows up later we don't resize >> > the fbcon to the panel's size. >> >> This issue can be solved using deffered fbdev registration, ie fbdev is >> registered after some connector(or specific one, up to you) becomes >> connected. > > Just jumping on on this part here: Deferred fbdev probe is merged now, > which means as long as really nothing is connected, fbdev won't force > anything. > > The exception is still analog outputs where we report "unknown", in that > case fbdev still tries to light that up right away, just in case. Not sure > that applies to the rpi with the tv-out. Yeah, TV-out reports unknown for us as well.
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