Hi Hans,
> The IRQ output of the bcm bt-device is really a level IRQ signal, which
> signals a logical high as long as the device's buffer contains data. Since
> the draining in the buffer is done in the tty driver, we cannot (easily)
> wait in a threaded interrupt handler for the draining, after which the
> IRQ should go low again.
>
> So instead we treat the IRQ as an edge interrupt. This opens the window
> for a theoretical race where we wakeup, read some data and then autosuspend
> *before* the IRQ has gone (logical) low, followed by the device just at
> that moment receiving more data, causing the IRQ to stay high and we never
> see an edge.
>
> Since we call pm_runtime_mark_last_busy() on every received byte, there
> should be plenty time for the IRQ to go (logical) low before we ever
> suspend, so this should never happen, but after commit 43fff7683468
> ("Bluetooth: hci_bcm: Streamline runtime PM code"), which has been reverted
> since, this was actually happening causing the device to get stuck in
> runtime suspend.
>
> The bcm bt-device actually has a workaround for this, if we set the
> pulsed_host_wake flag in the sleep parameters, then the device monitors
> if the host is draining the buffer and if not then after a timeout the
> device will pulse the IRQ line, causing us to see an edge, fixing the
> stuck in suspend condition.
>
> This commit sets the pulsed_host_wake flag to fix the (mostly theoretical)
> race caused by us treating the IRQ as an edge IRQ.
>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
> drivers/bluetooth/hci_bcm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
patch has been applied to bluetooth-stable tree.
Regards
Marcel
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