Messages in this thread | | | Date | Tue, 23 Aug 2022 08:06:05 +0200 | From | Takashi Iwai <> | Subject | Re: [REGRESSION 5.19.x] AMD HD-audio devices missing on 5.19 |
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On Tue, 23 Aug 2022 03:00:21 +0200, Jason Gunthorpe wrote: > > On Mon, Aug 22, 2022 at 04:12:59PM +0200, Takashi Iwai wrote: > > Hi, > > > > we've received regression reports about the missing HD-audio devices > > on AMD platforms, and this turned out to be caused by the commit > > 512881eacfa72c2136b27b9934b7b27504a9efc2 > > bus: platform,amba,fsl-mc,PCI: Add device DMA ownership management > > > > The details are found in openSUSE bugzilla: > > https://bugzilla.suse.com/show_bug.cgi?id=1202492 > > > > The problem seems to be that HD-audio (both onboard analog and HDMI) > > PCI devices are assigned to the same IOMMU group as AMD graphics PCI > > device, and once after the AMDGPU is initialized beforehand, those > > audio devices can't be probed since iommu_device_use_default_domain() > > returns -EBUSY. > > Can you describe exactly what drivers are involved in this? If it is > the above commit then several devices are sharing an iommu group and > one of them (well, the only one already attached, I suppose) has made > the group unsharable. > > With grep I don't see an obvious place where the AMDGPU driver would > mess with the iommu configuration, so I have no guess.
I have also no concrete clue, either :) At least, drivers/gpu/drm/amd/amdkfd/kfd_iommu.c calls amd_iommu_init_device(), and this invokes iommu_attach_group(), which may change group->domain. But it was just my wild guess, and it might be others, indeed.
> It would be good to have some debugging to confirm if it is > group->owner (should be impossible, suggests memory corruption if it > is) or group->domain != group->default_domain. > > Most likely it is the later, but I can't see how that could happen on > a system like this.. There is no obvious manipulation in AMDGPU, for > instance. > > So debugging to find the backtrace for exactly when > group->domain != group->default_domain > Occurs for the troubled group would be necessary.
OK, will try to build a test kernel with some debug prints and ask the reporters. It may take some time.
> If you know the group name it would be easy enough to cook a patch to > throw a warn on when group->domain changes > > > domain assignment. In anyway, disabling IOMMU works around the > > problem, and passing driver_managed_dma flag to the HD-audio driver > > was also confirmed to work around it, too. > > Disabling iommu removes the groups entirely, this disables the check. > > driver_managed_dma disables the check entirely - which raises the > question how the driver is even able to work.. > > If the domain is not the default_domain it is very surprising that DMA > can work at all. Since it does, something really odd has happened.
Yeah it's something odd ;)
I'm not sure whether the people tested HD-audio capability at all, but otherwise they might have noticed.
Takashi
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