From: "Pali Rohár" <pali@kernel.org>
To: "Jonas Dreßler" <verdre@v0yd.nl>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
Brian Norris <briannorris@chromium.org>,
Amitkumar Karwar <amitkarwar@gmail.com>,
Ganapathi Bhat <ganapathi017@gmail.com>,
Xinming Hu <huxinming820@gmail.com>,
Kalle Valo <kvalo@codeaurora.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Tsuchiya Yuto <kitakar@gmail.com>,
linux-wireless <linux-wireless@vger.kernel.org>,
netdev@vger.kernel.org,
Linux Kernel <linux-kernel@vger.kernel.org>,
linux-pci <linux-pci@vger.kernel.org>,
Maximilian Luz <luzmaximilian@gmail.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH 1/2] mwifiex: Use non-posted PCI register writes
Date: Thu, 30 Sep 2021 17:42:02 +0200 [thread overview]
Message-ID: <20210930154202.cvw3it3edv7pmqtb@pali> (raw)
In-Reply-To: <db583b3c-6bfc-d765-a588-eb47c76cea31@v0yd.nl>
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?
> 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...
next prev parent reply other threads:[~2021-09-30 15:42 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-30 12:37 [PATCH 0/2] mwifiex: Work around firmware bugs on 88W8897 chip Jonas Dreßler
2021-08-30 12:37 ` [PATCH 1/2] mwifiex: Use non-posted PCI register writes Jonas Dreßler
2021-08-30 12:49 ` Andy Shevchenko
2021-09-01 14:01 ` Jonas Dreßler
2021-09-01 15:47 ` Andy Shevchenko
2021-09-01 15:51 ` Pali Rohár
2021-09-01 16:51 ` Heiner Kallweit
2021-09-01 17:07 ` Johannes Berg
2021-09-01 19:07 ` Heiner Kallweit
2021-09-01 22:41 ` Bjorn Helgaas
2021-09-02 14:05 ` Bjorn Helgaas
2021-09-01 19:40 ` Brian Norris
2021-09-01 20:40 ` Andy Shevchenko
2021-09-01 21:04 ` Brian Norris
2021-09-01 21:07 ` Brian Norris
2021-09-18 7:37 ` Jonas Dreßler
2021-09-20 17:48 ` Brian Norris
2021-09-22 12:50 ` Jonas Dreßler
2021-09-23 15:28 ` Jonas Dreßler
2021-09-23 19:37 ` Andy Shevchenko
2021-09-23 19:41 ` Andy Shevchenko
2021-09-23 20:22 ` Pali Rohár
2021-09-30 15:38 ` Jonas Dreßler
2021-09-30 15:42 ` Pali Rohár [this message]
2021-09-30 16:14 ` Jonas Dreßler
2021-09-30 16:19 ` Pali Rohár
2021-09-30 16:22 ` Jonas Dreßler
2021-09-30 16:39 ` Pali Rohár
2021-08-30 12:37 ` [PATCH 2/2] mwifiex: Try waking the firmware until we get an interrupt Jonas Dreßler
2021-08-30 12:51 ` Andy Shevchenko
2021-08-30 12:55 ` Andy Shevchenko
2021-09-25 17:32 ` [PATCH 0/2] mwifiex: Work around firmware bugs on 88W8897 chip Pali Rohár
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