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    SubjectRe: [PATCH v2 2/2] mwifiex: Try waking the firmware until we get an interrupt
    Hi,

    On Sun, Oct 3, 2021 at 2:18 AM Jonas Dreßler <verdre@v0yd.nl> wrote:
    > So I think I have another solution that might be a lot more elegant, how
    > about this:
    >
    > try_again:
    > n_tries++;
    >
    > mwifiex_write_reg(adapter, reg->fw_status, FIRMWARE_READY_PCIE);
    >
    > if (wait_event_interruptible_timeout(adapter->card_wakeup_wait_q,
    > READ_ONCE(adapter->int_status) != 0,
    > WAKEUP_TRY_AGAIN_TIMEOUT) == 0 &&
    > n_tries < MAX_N_WAKEUP_TRIES) {
    > goto try_again;
    > }

    Isn't wait_event_interruptible_timeout()'s timeout in jiffies, which
    is not necessarily that predictable, and also a lot more
    coarse-grained than we want? (As in, if HZ=100, we're looking at
    precision on the order of 10ms, whereas the expected wakeup latency is
    ~6ms.) That would be OK for well-behaved PCI cases, where we never
    miss a write, but it could ~double your latency for your bad systems
    that will need more than one run of the loop.

    Also, feels like a do/while could be cleaner, but that's a lesser detail.

    > and then call wake_up_interruptible() in the mwifiex_interrupt_status()
    > interrupt handler.
    >
    > This solution should make sure we always keep wakeup latency to a minimum
    > and can still retry the register write if things didn't work.

    Brian

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