"Mark Pearson" <mpearson-lenovo@xxxxxxxxx> writes: > On Sun, Jul 14, 2024, at 10:38 PM, Baochen Qiang 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> > > We've tested this in the Lenovo lab using the T14 G5 AMD with a > 6.10.0-rc7+ kernel from wireless-next and this patch applied. > Previously we had stability issues under traffic load. With the patch > applied we can no longer reproduce the issue. > > Tested-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx> > > Can this be tagged for stable backporting? It's an important fix. I added cc stable to the commit message. I forgot to do it before I pushed my changes out, but it's in my local branch. -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
