On 2014ë 11ì 06ì¼ 18:29, Thierry Reding wrote: > On Thu, Nov 06, 2014 at 03:23:27PM +0900, Inki Dae wrote: >> On 2014ë 11ì 05ì¼ 23:38, Thierry Reding wrote: >>> On Tue, Nov 04, 2014 at 09:18:46PM +0400, Matwey V. Kornilov wrote: >>>> Hi, >>>> >>>> I run 3.18-rc3 kernel on BeagleBone Black. It doesn't have Exynos DRM >>>> of course, but I run multi-platform kernel where CONFIG_DRM_EXYNOS is >>>> set to 'y'. >>>> The issue here is that the platform probe/init goes to infinite loop >>>> as the following: >>>> >>>> [ 5.717343] platform exynos-drm: Driver exynos-drm requests probe >>>> deferral >>>> [ 5.726848] exynos-drm-ipp exynos-drm-ipp: drm ipp registered >>>> successfully. >>>> [ 5.734700] platform exynos-drm: Driver exynos-drm requests probe >>>> deferral >>>> [ 5.744044] exynos-drm-ipp exynos-drm-ipp: drm ipp registered >>>> successfully. >>>> [ 5.752010] platform exynos-drm: Driver exynos-drm requests probe >>>> deferral >>>> [ 5.761377] exynos-drm-ipp exynos-drm-ipp: drm ipp registered >>>> successfully. >>>> [ 5.769291] platform exynos-drm: Driver exynos-drm requests probe >>>> deferral >>>> >>>> It is quite unexpectable behavior. I would expect that the exynos-drm >>>> failed to initialize with 'no device' error. >>>> >>>> See also for the reference: >>>> https://bugzilla.kernel.org/show_bug.cgi?id=87691 >>> >>> The reason for this seems to be that Exynos DRM instantiates a dummy >>> device that it can bind to (see exynos_drm_init()). Now this code is >>> executed unconditonally, so the device will be created whether or not >>> the kernel/module runs on an Exynos SoC. The driver should really bind >>> to some real device rather than instantiating a dummy. Or if it must >>> bind to a dummy then the code needs to at least check that it's running >>> on an Exynos SoC before instantiating the dummy. >>> >> >> Right, I also think the problem is because we use a dummay device for >> Exynos drm. As you mentioned, this device can always be bound as long as >> Exynos drm driver is enabled even without real device. So this issue >> gives us that we need super device node again. Actually, I had already >> tried the use of the super device node like below for Exynos drm but >> other Samsung guys didn't want to use it. >> http://lists.freedesktop.org/archives/dri-devel/2014-April/056618.html >> >> I think now we have the reason that we should use super device node so I >> will try to support the super device for Exynos drm like other ARM drm >> drivers did. However, for this, I'd like to listen to other opinions >> for a while before that. > > Irrespective of any long-term solution you need to fix this as soon as > possible because this currently causes all sorts of weirdness when > booting a multi-platform kernel on non-Exynos boards. Probably the > easiest for now would be to add some soc_is_exynos*() check at the very > beginning of exynos_drm_init().
Got it. Thanks, Inki Dae > > Thierry >
