exynos-drm registration: infinite loop

[Matwey V. Kornilov]

2014-11-05 17:38 GMT+03:00 Thierry Reding <thierry.reding at gmail.com>:
> 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.
>
> Thierry

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.

-- 
With best regards,
Matwey V. Kornilov
http://blog.matwey.name
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