On Mon, Aug 30, 2021 at 5:37 AM Jonas Dreßler <verdre@xxxxxxx> wrote: > > On the 88W8897 card it's very important the TX ring write pointer is > updated correctly to its new value before setting the TX ready > interrupt, otherwise the firmware appears to crash (probably because > it's trying to DMA-read from the wrong place). > > Since PCI uses "posted writes" when writing to a register, it's not > guaranteed that a write will happen immediately. That means the pointer > might be outdated when setting the TX ready interrupt, leading to > firmware crashes especially when ASPM L1 and L1 substates are enabled > (because of the higher link latency, the write will probably take > longer). > > So fix those firmware crashes by always forcing non-posted writes. We do > that by simply reading back the register after writing it, just as a lot > of other drivers do. > > There are two reproducers that are fixed with this patch: > > 1) During rx/tx traffic and with ASPM L1 substates enabled (the enabled > substates are platform dependent), the firmware crashes and eventually a > command timeout appears in the logs. That crash is fixed by using a > non-posted write in mwifiex_pcie_send_data(). > > 2) When sending lots of commands to the card, waking it up from sleep in > very quick intervals, the firmware eventually crashes. That crash > appears to be fixed by some other non-posted write included here. > > Signed-off-by: Jonas Dreßler <verdre@xxxxxxx> This might be good for many cases, but please read this commit: https://git.kernel.org/linus/062e008a6e83e7c4da7df0a9c6aefdbc849e2bb3 mwifiex: pcie: use posted write to wake up firmware It's very much intentional that this is a posted write in some cases. Without ensuring this doesn't regress, NAK from me. Brian
