On Wednesday 01 September 2021 16:01:54 Jonas Dreßler wrote: > On 8/30/21 2:49 PM, Andy Shevchenko wrote: > > On Mon, Aug 30, 2021 at 3:38 PM 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 might be outdated when setting the TX ready interrupt, leading to 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. > > > > Thanks for all this work! > > > > Nevertheless, do we have any commits that may be a good candidate to > > be in the Fixes tag here? > > > > I don't think there's any commit we could point to, given that the bug is > probably somewhere in the firmware code. Then please add Cc: stable@xxxxxxxxxxxxxxx tag into commit message. Such bugfix is a good candidate for backporting into stable releases. > >> Signed-off-by: Jonas Dreßler <verdre@xxxxxxx>
