[AMD Official Use Only - General] I would also highly recommend this to be tested with another compositor (Like Weston/Sway etc) Regards Shashank -----Original Message----- From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx> Sent: 26 January 2023 15:12 To: Slivka, Danijel <Danijel.Slivka@xxxxxxx>; Thomas Zimmermann <tzimmermann@xxxxxxx> Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; dri-devel <dri-devel@xxxxxxxxxxxxxxxxxxxxx>; Sharma, Shashank <Shashank.Sharma@xxxxxxx> Subject: Re: Amdgpu module is references even after unbinding the vtcon Hi Danijel, can you also double check that GDM/X is still capable of acquiring a DMA-buf file descriptor for the buffer (e.g. that we have a DMA-buf handle for it while they are started). And that handover from fbdev to GDM/X is flicker free? Thanks, Christian. Am 26.01.23 um 14:44 schrieb Slivka, Danijel: > [AMD Official Use Only - General] > > Hi Christian, > > I have tested the proposed patch, the issue is not reproducible and everything else seems to work fine. > > BR, > Danijel > >> -----Original Message----- >> From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx> >> Sent: Thursday, January 26, 2023 1:20 PM >> To: Slivka, Danijel <Danijel.Slivka@xxxxxxx>; Thomas Zimmermann >> <tzimmermann@xxxxxxx> >> Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; dri-devel <dri- >> devel@xxxxxxxxxxxxxxxxxxxxx>; Sharma, Shashank >> <Shashank.Sharma@xxxxxxx> >> Subject: Re: Amdgpu module is references even after unbinding the >> vtcon >> >> Am 26.01.23 um 10:49 schrieb Slivka, Danijel: >>> [AMD Official Use Only - General] >>> >>> Hi Thomas, >>> >>> I have checked what you mentioned. >>> When loading amdgpu we call drm_client_init() during fbdev setup >>> [1], the >> refcnt for drm_kms_helper increases from 3 -> 4. >>> When we unbind vtcon, refcnt for drm_kms_helper drops 4 -> 3, but >>> the >> drm_client_release() [2] is not called. >>> The drm_client_release() is called only when unloading the amdgpu driver. >>> >>> Is this expected? >> Yes, the client can't be released because it is possible that the >> vtcon is bound to this fbdev again. >> >> Please test the handle work around I've send around internally. At >> least for me that approach seems to work. >> >> Regards, >> Christian. >> >>> There is a comment for drm_client_release with regards to fbdev : >>> * This function should only be called from the unregister callback. An exception >>> * is fbdev which cannot free the buffer if userspace has open file descriptors. >>> >>> Could this be relevant for our use case, although as >>> Application/X/GDM are >> stopped at that point and no fd should be open. >>> Thank you, >>> BR, >>> Danijel >>> >>>> -----Original Message----- >>>> From: Thomas Zimmermann <tzimmermann@xxxxxxx> >>>> Sent: Wednesday, January 25, 2023 8:48 PM >>>> To: Christian König <ckoenig.leichtzumerken@xxxxxxxxx> >>>> Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Slivka, Danijel >>>> <Danijel.Slivka@xxxxxxx>; dri-devel >>>> <dri-devel@xxxxxxxxxxxxxxxxxxxxx>; Sharma, Shashank >>>> <Shashank.Sharma@xxxxxxx> >>>> Subject: Re: Amdgpu module is references even after unbinding the >>>> vtcon >>>> >>>> Hi Christian >>>> >>>> Am 24.01.23 um 15:12 schrieb Christian König: >>>>> Hi Thomas, >>>>> >>>>> we ran into a problem with the general fbcon/fbdev implementation >>>>> and though that you might have some idea. >>>>> >>>>> What happens is the following: >>>>> 1. We load amdgpu and get our normal fbcon. >>>>> 2. fbcon allocates a dump BO as backing store for the console. >>>>> 3. GDM/X/Applications start, new framebuffers are created BOs >>>>> imported, exported etc... >>>>> 4. Somehow X or GDM iterated over all the framebuffer objects the >>>>> kernels knows about and export them as DMA-buf. >>>>> 5. Application/X/GDM are stopped, handles closed, framebuffers >>>>> released etc... >>>>> 6. We unbind vtcon. >>>>> >>>>> At this point the amdgpu module usually has a reference count of 0 >>>>> and can be unloaded, but since GDM/X/Whoever iterated over all the >>>>> known framebuffers and exported them as DMA-buf (for whatever >>>>> reason >>>>> idk) we now still have an exported DMA-buf and with it a reference >>>>> to the >> module. >>>>> Any idea how we could prevent that? >>>> Here's another stab in the dark. >>>> >>>> The big difference between old-style fbdev and the new one is that >>>> the old fbdev setup (e.g., radeon) allocates a GEM object and puts >>>> together the fbdev data structures from the BO in a fairly hackish >>>> way. The new style uses an in-kernel client with a file to allocate >>>> the BO via dumb buffers; and holds a reference to the DRM module. >>>> >>>> Maybe the reference comes from the in-kernel DRM client itself. [1] >>>> Check if the client resources get released [2] when you unbind vtcon. >>>> >>>> Best regards >>>> Thomas >>>> >>>> [1] >>>> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_ >>>> cl >>>> ient.c#L87 >>>> [2] >>>> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_ >>>> cl >>>> ient.c#L16 >>>> 0 >>>> >>>>> Thanks, >>>>> Christian. >>>> -- >>>> Thomas Zimmermann >>>> Graphics Driver Developer >>>> SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, >>>> Germany (HRB 36809, AG Nürnberg) >>>> Geschäftsführer: Ivo Totev
