Messages in this thread | | | Subject | Re: [PATCH 1/2] mwifiex: Use non-posted PCI register writes | From | Jonas Dreßler <> | Date | Thu, 30 Sep 2021 18:14:04 +0200 |
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On 9/30/21 5:42 PM, Pali Rohár wrote: > On Thursday 30 September 2021 17:38:43 Jonas Dreßler wrote: >> On 9/23/21 10:22 PM, Pali Rohár wrote: >>> On Thursday 23 September 2021 22:41:30 Andy Shevchenko wrote: >>>> On Thu, Sep 23, 2021 at 6:28 PM Jonas Dreßler <verdre@v0yd.nl> wrote: >>>>> On 9/22/21 2:50 PM, Jonas Dreßler wrote: >>>> >>>> ... >>>> >>>>> - Just calling mwifiex_write_reg() once and then blocking until the card >>>>> wakes up using my delay-loop doesn't fix the issue, it's actually >>>>> writing multiple times that fixes the issue >>>>> >>>>> These observations sound a lot like writes (and even reads) are actually >>>>> being dropped, don't they? >>>> >>>> It sounds like you're writing into a not ready (fully powered on) device. >>> >>> This reminds me a discussion with Bjorn about CRS response returned >>> after firmware crash / reset when device is not ready yet: >>> https://lore.kernel.org/linux-pci/20210922164803.GA203171@bhelgaas/ >>> >>> Could not be this similar issue? You could check it via reading >>> PCI_VENDOR_ID register from config space. And if it is not valid value >>> then card is not really ready yet. >>> >>>> To check this, try to put a busy loop for reading and check the value >>>> till it gets 0. >>>> >>>> Something like >>>> >>>> unsigned int count = 1000; >>>> >>>> do { >>>> if (mwifiex_read_reg(...) == 0) >>>> break; >>>> } while (--count); >>>> >>>> >>>> -- >>>> With Best Regards, >>>> Andy Shevchenko >> >> I've tried both reading PCI_VENDOR_ID and the firmware status using a busy >> loop now, but sadly none of them worked. It looks like the card always >> replies with the correct values even though it sometimes won't wake up after >> that. >> >> I do have one new observation though, although I've no clue what could be >> happening here: When reading PCI_VENDOR_ID 1000 times to wakeup we can >> "predict" the wakeup failure because exactly one (usually around the 20th) >> of those 1000 reads will fail. > > What does "fail" means here?
ioread32() returns all ones, that's interpreted as failure by mwifiex_read_reg().
> >> Maybe the firmware actually tries to wake up, >> encounters an error somewhere in its wakeup routines and then goes down a >> special failure code path. That code path keeps the cards CPU so busy that >> at some point a PCI_VENDOR_ID request times out? >> >> Or well, maybe the card actually wakes up fine, but we don't receive the >> interrupt on our end, so many possibilities...
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