Baochen Qiang <quic_bqiang@xxxxxxxxxxx> wrote: > In transmit path, it is likely that the iova is not aligned to PCIe TLP > max payload size, which is 128 for WCN7850. Normally in such cases hardware > is expected to split the packet into several parts in a manner such that > they, other than the first one, have aligned iova. However due to hardware > limitations, WCN7850 does not behave like that properly with some specific > unaligned iova in transmit path. This easily results in target hang in a > KPI transmit test: packet send/receive failure, WMI command send timeout > etc. Also fatal error seen in PCIe level: > > ... > Capabilities: ... > ... > DevSta: ... FatalErr+ ... > ... > ... > > Work around this by manually moving/reallocating payload buffer such that > we can map it to a 128 bytes aligned iova. The moving requires sufficient > head room or tail room in skb: for the former we can do ourselves a favor > by asking some extra bytes when registering with mac80211, while for the > latter we can do nothing. > > Moving/reallocating buffer consumes additional CPU cycles, but the good news > is that an aligned iova increases PCIe efficiency. In my tests on some X86 > platforms the KPI results are almost consistent. > > Since this is seen only with WCN7850, add a new hardware parameter to > differentiate from others. > > Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3 > > Signed-off-by: Baochen Qiang <quic_bqiang@xxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Tested-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx> > Signed-off-by: Kalle Valo <quic_kvalo@xxxxxxxxxxx> Patch applied to ath-current branch of ath.git, thanks. 38055789d151 wifi: ath12k: use 128 bytes aligned iova in transmit path for WCN7850 -- https://patchwork.kernel.org/project/linux-wireless/patch/20240715023814.20242-1-quic_bqiang@xxxxxxxxxxx/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
