Re: [PATCH v6 4/4] ALSA: usb-audio: qcom: fix xfer ring IOMMU unmap on 16K+ page kernels

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] ALSA: usb-audio: qcom: missing Fixes trailer for 16K+ page ring
  fix
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commit 7088c3c3566e5837438b6b83c5b7547812406f63
Author: Wesley Cheng <wesley.cheng@oss.qualcomm.com>

> ALSA: usb-audio: qcom: fix xfer ring IOMMU unmap on 16K+ page kernels
>
> TRB_SEGMENT_SIZE is hardcoded to 4096 bytes, but on kernels built with
> a larger PAGE_SIZE (e.g. 16K or 64K page arches) the IOMMU still maps
> and unmaps in units of PAGE_SIZE. The driver maps the page containing
> the ring segment, but reports the start of that page as the ring
> address and PAGE_SIZE as its size. This is only correct if the segment
> starts at offset 0 in its page.
>
> For both the transfer rings and the event ring, add that offset to the
> mapped iova before sending it to the ADSP over QMI, so the reported
> address points at the start of the segment rather than the start of
> its page. Also report the sg entry length (TRB_SEGMENT_SIZE) instead of
> PAGE_SIZE as the ring size. The offset is taken from the sg entry
> rather than from the ring's DMA address, because when xHCI is behind an
> IOMMU that address is an IOVA, and its low bits need not match the
> offset within the page.
>
> With the offset added, IOVA_MASK() on the reported iova no longer gives
> the page-aligned iova that was mapped. Have uaudio_endpoint_setup() pass
> back the mapped iova, and use it for the cached data/sync_xfer_ring_va
> and the drop_sync_ep/drop_data_ep unmaps.
>
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Wesley Cheng <wesley.cheng@oss.qualcomm.com>

[Severity: Low]
Since this fixes a bug in the transfer and event ring IOVA setup and
unmapping, should it include a Fixes tag?

  Fixes: 326bbc348298 ("ALSA: usb-audio: qcom: Introduce QC USB SND offloading support")

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Sashiko AI review · https://sashiko.dev/#/patchset/20261109-16k_offload_v1_b4-v6-0-858c6e0e007d@oss.qualcomm.com?part=4