On Tue, Sep 14, 2021 at 01:48:12PM +0200, Jonas Dreßler 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). The issue is present in
> the latest firmware version 15.68.19.p21 of the pcie+usb card.
Please, be consistent in the commit message(s) and the code (esp. if the term
comes from a specification).
Here, PCIe (same in the code, at least that I have noticed, but should be done
everywhere).
> 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 might be outdated when setting the TX ready interrupt, leading to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 using a non-posted write for
> this specific register write. We do that by simply reading back the
> register after writing it, just as a few other PCI drivers do.
>
> This fixes a bug where during rx/tx traffic and with ASPM L1 substates
Ditto. TX/RX.
> enabled (the enabled substates are platform dependent), the firmware
> crashes and eventually a command timeout appears in the logs.
Should it have a Fixes tag?
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jonas Dreßler <verdre@xxxxxxx>
...
> - /* Write the TX ring write pointer in to reg->tx_wrptr */
> - if (mwifiex_write_reg(adapter, reg->tx_wrptr,
> - card->txbd_wrptr | rx_val)) {
> + /* Write the TX ring write pointer in to reg->tx_wrptr.
> + * The firmware (latest version 15.68.19.p21) of the 88W8897
> + * pcie+usb card seems to crash when getting the TX ready
> + * interrupt but the TX ring write pointer points to an outdated
> + * address, so it's important we do a non-posted write here to
> + * force the completion of the write.
> + */
> + if (mwifiex_write_reg_np(adapter, reg->tx_wrptr,
> + card->txbd_wrptr | rx_val)) {
> mwifiex_dbg(adapter, ERROR,
> "SEND DATA: failed to write reg->tx_wrptr\n");
> ret = -1;
I'm not sure how this is not a dead code.
On top of that, I would rather to call old function and explicitly put the
dummy read after it.
/* Write the TX ring write pointer in to reg->tx_wrptr */
if (mwifiex_write_reg(adapter, reg->tx_wrptr,
card->txbd_wrptr | rx_val)) {
...eliminate dead code in the following patch(es)...
}
+ /* The firmware (latest version 15.68.19.p21) of the 88W8897
+ * pcie+usb card seems to crash when getting the TX ready
+ * interrupt but the TX ring write pointer points to an outdated
+ * address, so it's important we do a non-posted write here to
+ * force the completion of the write.
+ */
mwifiex_read_reg(...);
Now, since I found the dummy read function to be present, perhaps you need to
dive more into the code and understand why it exists.
--
With Best Regards,
Andy Shevchenko
