Re: [PATCH 0/2] iommu/sun50i: Don't report TLB prefetch walks as page faults

["Jernej Škrabec" <jernej.skrabec@gmail.com>]

Dne torek, 10. november 2026 ob 07:05:16 Srednjeevropski standardni čas je Arun Iyengar via B4 Relay napisal(a):
> On an H616 with a display scanning out, the IOMMU reports page faults
> with master -1 at the IOVA right after the end of the framebuffer: once
> at the first fbcon frame, and then once per frame for a while after
> each TLB flush, e.g. while a video decoder frees its buffers. They are
> failed walks of the TLB prefetcher, which the hardware flags with bit 31
> of the page table interrupt registers and no master bit. Patch 1 stops
> reporting them. Patch 2 makes the remaining fault messages say which
> walk failed and what the interrupt register held.
> 
> Tested on an Orange Pi Zero2 (H616) with HDMI forced on at 1024x768 and
> three 4K H.264 decodes through cedrus, on 7.3 kernels with and without
> the patches:
> - without: 214 "Page fault ... (master -1, dir rd)" lines;
> - with: none, no "Page fault" line at all, and no decode errors or
>   timeouts.
> Since the patched kernel prints every fault that is not a masterless
> prefetch walk, this also shows that the hardware sets bit 31 for these
> walks.

First off, display engine isn't in merged yet. Second, I don't observe any
such issues with my wip H616 code.

I think it's best to wait until driver is merged and can be retested and
merged then, if needed.

Best regards,
Jernej

> 
> These patches were developed with Claude (Anthropic) as a coding
> assistant. It investigated the problem and wrote the code and the commit
> messages; I reviewed them, and they were tested on an Orange Pi Zero2
> (H616) as described above.
> 
> ---
> Arun Iyengar (2):
>       iommu/sun50i: Don't report TLB prefetches of unmapped pages as faults
>       iommu/sun50i: Print the page table level and status of a fault
> 
>  drivers/iommu/sun50i-iommu.c | 50 ++++++++++++++++++++++++++++++++++----------
>  1 file changed, 39 insertions(+), 11 deletions(-)
> ---
> base-commit: 2cf4be57b301ed2d7af82e70cff5dfd96894d8de
> change-id: 20261110-sun50i-iommu-prefetch-85cc9ecff559
> 
> Best regards,
> --  
> Arun Iyengar <aiyengar1990@gmail.com>
> 
> 
>