Re: [PATCH ath-next] wifi: ath10k: snoc: use memcpy_fromio() for MSA ramdump

[Rameshkumar Sundaram <rameshkumar.sundaram@oss.qualcomm.com>]

On 7/27/2026 12:56 PM, Linghui Wu wrote:
> On WCN3990/SNOC the MSA region is mapped with devm_memremap(MEMREMAP_WT).
> On arm64 such a mapping is not Normal-cacheable, so unaligned accesses to
> it are not permitted. ath10k_msa_dump_memory() copies the region with a
> plain memcpy(), whose optimized __pi_memcpy_generic implementation issues
> wide/unaligned loads. This triggers an alignment fault (FSC=0x21) Oops in
> ath10k_snoc_fw_crashed_dump() while collecting the devcoredump:
> 
>    Unable to handle kernel paging request ... FSC=0x21: alignment fault
>    pc : __pi_memcpy_generic
>    lr : ath10k_snoc_fw_crashed_dump [ath10k_snoc]
> 
> The Oops both leaves the firmware RAM dump buffer zeroed (no dump is
> captured) and crashes the kernel, which in turn breaks modem SSR
> recovery.
> 
> Use memcpy_fromio(), which only performs accesses that are valid for such
> a device-memory mapping. The generic memcpy_fromio() implementation aligns
> the source before issuing word-sized reads and stores the destination with
> put_unaligned(), so it is also safe for the coherent DMA allocation used on
> the non-reserved-memory path. ath11k and ath12k use the same pattern
> when copying target memory into crash dumps, so call it unconditionally
> here too.
> The MEMREMAP_WT pointer is a plain void *, so an explicit __iomem cast is
> needed; use __force to keep sparse happy.
> 
> Tested-on: WCN3990 hw1.0 SNOC WLAN.HL.3.3.7.c5-00107-QCAHLSWMTPL-1
> 
> Fixes: 3f14b73c3843 ("ath10k: Enable MSA region dump support for WCN3990")
> Signed-off-by: Linghui Wu <linghui.wu@oss.qualcomm.com>
Reviewed-by: Rameshkumar Sundaram <rameshkumar.sundaram@oss.qualcomm.com>