On Thu, 21 Aug 2014 11:52:03 +0200 Thierry Reding <thierry.reding@xxxxxxxxx> 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. I was talking about the external RGB to HDMI encoder, should the driver for this encoder (which is not on On Chip block) be compiled statically too ? > > 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). For now, I wait until there is a device connected on the RGB connector (connector status set to connector_status_connected) before creating an fbdev. It might not be the cleanest way to solve this issue, but it works :-). > 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). Here [1] is a proposal for notification support in the drm_panel infrastructure (which is not that complicated), and here [2] is how I use it in my atmel-hlcdc driver to generate hotplug events. Let me know if you want me to submit a proper patch series... Best Regards, Boris [1]http://code.bulix.org/scq4g3-86804 [2]http://code.bulix.org/7dg501-86805 -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- 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
