Annoying AMDGPU boot-time warning due to simplefb / amdgpu resource clash

[Javier Martinez Canillas]

On 6/28/22 14:41, Jocelyn Falempe wrote:
> On 28/06/2022 10:43, Thomas Zimmermann wrote:

[snip]

>>
>> Unfortunately, this currently only works if a driver is bound to the 
>> platform device. Without simpledrm or simplefb, amdgpu won't find the 
>> platform device to remove.
>>
>> I guess, what happens on your system is that sysfb create a device for 
>> the EFI framebuffer and then amdgpu comes and doesn't find it for 
>> removal. And later you see these warnings because BOOTFB is still around.
>>
>> Javier already provided patches for this scenario, which are in the DRM 
>> tree. From drm-next, please cherry-pick
>>
>>    0949ee75da6c ("firmware: sysfb: Make sysfb_create_simplefb() return a 
>> pdev pointer")
>>
>>    bc824922b264 ("firmware: sysfb: Add sysfb_disable() helper function")
>>
>>    873eb3b11860 ("fbdev: Disable sysfb device registration when removing 
>> conflicting FBs")
>>
>> for testing. With these patches, amdgpu will find the sysfb device and 
>> unregister it.
>>
>> The patches are queued up for the next merge window. If they resolve the 
>> issue, we'll already send with the next round of fixes.
> 
> I was able to reproduce the warning with kernel v5.19-rc4, a radeon GPU 
> and the following config:
>
> CONFIG_SYSFB=y
> CONFIG_SYSFB_SIMPLEFB=y
> # CONFIG_DRM_SIMPLEDRM is not set
> # CONFIG_FB_SIMPLE is not set
>

Yes, and this could happen even if both drivers (e.g: simplefb and amdgpu)
are enabled but built-in. For example, if amdgpu probes before simplefb.

> After applying the 3 patches you mentioned, the issue is resolved. (at 
> least on my setup).
>

Thanks for testing Jocelyn! I've pushed the patches to drm-misc-fixes now.

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat