On 08/21/2014 03:21 PM, Thierry Reding wrote: > On Thu, Aug 21, 2014 at 12:32:43PM +0200, Andrzej Hajda wrote: >> On 08/21/2014 11:52 AM, Thierry Reding wrote: >>> On Thu, Aug 21, 2014 at 11:41:59AM +0200, Boris BREZILLON wrote: >>>> On Thu, 21 Aug 2014 11:04:07 +0200 >>>> Thierry Reding <thierry.reding@xxxxxxxxx> wrote: >>>> >>>>> On Thu, Aug 21, 2014 at 10:37:06AM +0200, Boris BREZILLON wrote: >>>>>> Hi Ludovic, >>>>>> >>>>>> On Thu, 21 Aug 2014 10:16:19 +0200 >>>>>> Ludovic Desroches <ludovic.desroches@xxxxxxxxx> wrote: >>>>>> >>>>>>> Hi Boris, >>>>>>> >>>>>>> You can add >>>>>>> >>>>>>> Tested-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx> >>>>>> Thanks for testing this driver. >>>>>> >>>>>>> Only one issue but not related to your patches, you can't display >>>>>>> quickly the bootup logo since the panel detection takes too much >>>>>>> time. >>>>>> Yes, actually this is related to the device probe order: the >>>>>> hlcdc-display-controller device is probed before the simple-panel, thus >>>>>> nothing is detected on the RGB connector (I use of_drm_find_panel to >>>>>> check for panel availability) when the display controller is >>>>>> instantiated. I rely on the default polling infrastructure provided by >>>>>> the DRM/KMS framework which polls for a new connector every 10s, and >>>>>> this is far more than you kernel boot time. >>>>>> >>>>>> Do anyone see a solution to reduce this delay (without changing the >>>>>> polling interval). I thought we could add a notifier infrastructure to >>>>>> the DRM panel framework, but I'm not sure this is how you want things >>>>>> done... >>>>> Other drivers return -EPROBE_DEFER when a panel hasn't been registered >>>>> yet. This will automatically take care of ordering things in a way that >>>>> DRM/KMS will only be initialized after the panel has been probed. >>>> Actually I'd like to avoid doing this with a deferred probe, because, >>>> AFAIU, the remote endpoint is not tightly linked with the display >>>> controller driver (I mean the display controller can still be >>>> initialized without having a display connected on it). >>>> Moreover the atmel dev kit I'm using has an HDMI bridge connected on >>>> the same RGB connector and I'd like to use it in a near future. >>>> Returning -EPROBE_DEFER in case of several devices connected on the >>>> same connector implies that I'll have to wait for all the remote >>>> end-points to be available before my display controller could be >>>> instantiated. >>>> >>>> While this could be acceptable when all drivers are statically linked >>>> in the kernel, it might be problematic when you're using modules, >>>> meaning that you won't be able to display anything on your LCD panel >>>> until your HDMI bridge module has been loaded. >>> No. HDMI should be using proper hotplugging anyway, hence it should be >>> always be loaded anyway. You're in for a world of pain if you think you >>> can run DRM with a driver that's composed of separate kernel modules. >>> >>> Also if you don't want to use deferred probe, then you're in for the >>> full hotplugging panel dance and that implies that you need to fix a >>> bunch of things in DRM (one being the framebuffer console instantiation >>> that I referred to in the other thread). You also can't be using the >>> current device tree bindings because they all assume a dependency from >>> the display controller/output to the panel. For hotplugging you'd need >>> the dependency the other way around (the panel needs to refer to the >>> output by phandle). >> I have tested panel as a module in exynos-dsi + panel-s6e8aa0 >> configuration, everything works. There is a workaround for fb console >> not being reconfigurable, but it does not make thing worse than before. >> And I do not see a problem with phandles, ie in DT they point both ways, >> according to binding advices at the time, but in the code it is display >> controller/encoder which is looking for the panel. > That works because it's DSI. And we have attach/detach callbacks for > DSI. We don't have those for regular panels, so we'd need to find a way > to add that. Maybe I have misread your answer, but you showed it as very difficult/painful process: "hotplugging panel dance", "fix a bunch of things in DRM". In fact we are missing here only good notifications about panel appearance. > > The way that this currently works is that an encoder/connector driver > looks up the panel and attaches it to itself. If you allow panels to be > hotpluggable, then they have no knowledge about what they are connected > to, so there needs to be a way to inject that knowledge so that they can > attach to a connector. I do not understand that. Currently it is the connector who looks for the panel and attaches it. So the scenario, after adding panel tracking, could be: - encoder parses its phandle to panel, and start tracking appearance of the panel identified by this phandle, - when panel appears encoder callback is called, and encoder attaches the panel, - when panel wants to disappear encoder callback is called, encoder detaches the panel. All this I have already presented together with generic interface tracker [1]. Regards Andrzej [1]: https://lkml.org/lkml/2014/4/30/345 > > Thierry -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
