On Thu, Nov 06, 2014 at 03:23:27PM +0900, Inki Dae wrote: > On 2014년 11월 05일 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(). Thierry
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