# Re: \[PATCH v10 1/2\] net: airoha: npu: fix missing streaming DMA mask

- From: Daniel Pawlik \<hidden\>
- Date: 2026-08-23 10:42:14 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/08/17449666
- Thread: https://ratatoskr.run/netdev/2026/08/17437451/t.md

```text
Hi,

I tested both patches independently:

- Patch 1 alone (DMA mask): NPU reports version 0.0 - probe fails.
  The streaming mask is correct but 24-byte buffers still bounce
  through swiotlb, and the NPU can't write to that address range.

- Patch 2 alone (cacheline buffers): NPU reports version 0.1111 -
  works. Cache-line-aligned allocations bypass swiotlb entirely.

So patch 2 is the essential fix, but patch 1 is still good to have as
a defensive measure - without a proper streaming DMA mask, any
future sub-cacheline streaming mapping would silently break.

Dan

sob., 22 sie 2026 o 21:27 Jakub Kicinski [ref] napisał(a):
>
> On Thu, 20 Aug 2026 10:59:40 +0200 Daniel Pawlik wrote:
> > The driver calls dma_set_coherent_mask() but never dma_set_mask(),
> > leaving the streaming DMA mask at the bus default. On the non-coherent
> > EN7581 platform (Cortex-A53), this causes the NPU mailbox to hang
> > after approximately 41 calls when using streaming DMA mappings.
>
> Can you confirm if patch 2 is still needed after this fix?



--
Z poważaniem,
Daniel Pawlik
```