From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: "Jonas Dreßler" <verdre@v0yd.nl>
Cc: "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>,
"open list:TI WILINK WIRELES..." <linux-wireless@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
"Linux Kernel Mailing List" <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>,
"Pali Rohár" <pali@kernel.org>
Subject: Re: [PATCH 2/2] mwifiex: Try waking the firmware until we get an interrupt
Date: Mon, 30 Aug 2021 15:51:43 +0300 [thread overview]
Message-ID: <CAHp75Vf-ekdTh=86nR7wqufFPmEb5bve0hf1Oq_k_OAJCkNvWg@mail.gmail.com> (raw)
In-Reply-To: <20210830123704.221494-3-verdre@v0yd.nl>
On Mon, Aug 30, 2021 at 3:39 PM Jonas Dreßler <verdre@v0yd.nl> wrote:
>
> It seems that the firmware of the 88W8897 card sometimes ignores or
> misses when we try to wake it up by reading the firmware status
> register. This leads to the firmware wakeup timeout expiring and the
> driver resetting the card because we assume the firmware has hung up or
> crashed (unfortunately that's not unlikely with this card).
>
> Turns out that most of the time the firmware actually didn't hang up,
> but simply "missed" our wakeup request and doesn't send us an AWAKE
didn't
> event.
>
> Trying again to read the firmware status register after a short timeout
> usually makes the firmware wake we up as expected, so add a small retry
wake up
> loop to mwifiex_pm_wakeup_card() that looks at the interrupt status to
> check whether the card woke up.
>
> The number of tries and timeout lengths for this were determined
> experimentally: The firmware usually takes about 500 us to wake up
> after we attempt to read the status register. In some cases where the
> firmware is very busy (for example while doing a bluetooth scan) it
> might even miss our requests for multiple milliseconds, which is why
> after 15 tries the waiting time gets increased to 10 ms. The maximum
> number of tries it took to wake the firmware when testing this was
> around 20, so a maximum number of 50 tries should give us plenty of
> safety margin.
>
> A good reproducer for this issue is letting the firmware sleep and wake
> up in very short intervals, for example by pinging an device on the
a device
> network every 0.1 seconds.
...
> + /* Access the fw_status register to wake up the device.
> + * Since the 88W8897 firmware sometimes appears to ignore or miss
> + * that wakeup request, we continue trying until we receive an
> + * interrupt from the card.
> + */
> + do {
> + if (mwifiex_write_reg(adapter, reg->fw_status, FIRMWARE_READY_PCIE)) {
> + mwifiex_dbg(adapter, ERROR,
> + "Writing fw_status register failed\n");
> + return -1;
> + }
> +
> + n_tries++;
> +
> + if (n_tries <= 15)
> + usleep_range(400, 700);
> + else
> + msleep(10);
> + } while (n_tries <= 50 && READ_ONCE(adapter->int_status) == 0);
NIH read_poll_timeout() from iopoll.h.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2021-08-30 12:52 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
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 [this message]
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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