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
On Tue, Nov 04, 2014 at 09:18:46PM +0400, Matwey V. Kornilov wrote:
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.
Thierry
2014-11-05 17:38 GMT+03:00 Thierry Reding thierry.reding@gmail.com:
Could it be fixed somehow?
By the way, I am not sure that exynos_drm_match_add behaves correctly. It returns EPROBE_DEFER when there are no matches, but it doesn't check (probably can not check) whether all the probes have been run.
On 2014년 11월 05일 23:38, Thierry Reding wrote:
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.
Thanks, Inki Dae
On 2014년 11월 06일 17:03, Andrzej Hajda wrote:
Yes, we can do it simply. However, I'm not still clear to handle these issues in this manner because if we use the super device which is the most generic way then Exynos drm can have real device node so we don't need such exception codes anymore. And with the super device, I'm not sure whether there are other issues or not we can face but it would be enough to consider only generic ways.
Anyway, I will decide how to handle Exynos drm device after listening to more other opinions.
Thanks, Inki Dae
2014-11-06 11:45 GMT+03:00 Inki Dae inki.dae@samsung.com:
However, what is about CONFIG_DRM_EXYNOS = 'm' ? I suppose that the super device and the appropriate record in dts will make alias and auto-load work.
On 2014년 11월 06일 17:49, Matwey V. Kornilov wrote:
I'm not sure what is your concern but with the super device, Exynos drm driver will also support legacy way so it would have no any dt broken. And I think now the auto-load already works well so any problem wouldn't be incurred with the super device. Is there my missing something ?
Thanks, Inki Dae
On Thu, Nov 06, 2014 at 03:23:27PM +0900, Inki Dae wrote:
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
dri-devel@lists.freedesktop.org
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Andrzej Hajda -
Inki Dae -
Matwey V. Kornilov -
Thierry Reding