On Wed, Aug 30, 2023 at 06:14:03PM -0700, Stephen Boyd wrote:
> It's possible for interrupts to get significantly delayed to the point
> that callers of intel_scu_ipc_dev_command() and friends can call the
> function once, hit a timeout, and call it again while the interrupt
> still hasn't been processed. This driver will get seriously confused if
> the interrupt is finally processed after the second IPC has been sent
> with ipc_command(). It won't know which IPC has been completed. This
> could be quite disastrous if calling code assumes something has happened
> upon return from intel_scu_ipc_dev_simple_command() when it actually
> hasn't.
>
> Let's avoid this scenario by simply returning -EBUSY in this case.
> Hopefully higher layers will know to back off or fail gracefully when
> this happens. It's all highly unlikely anyway, but it's better to be
> correct here as we have no way to know which IPC the status register is
> telling us about if we send a second IPC while the previous IPC is still
> processing.
> +static bool intel_scu_ipc_busy(struct intel_scu_ipc_dev *scu)
static int ?
> +{
> + u8 status;
> +
> + status = ipc_read_status(scu);
> + if (status & IPC_STATUS_BUSY) {
> + dev_err(&scu->dev, "device is busy\n");
1. Wouldn't it exaggerate the logs? Shouldn't be rate limited?
2. OTOH if we return -EBUSY directly from here, do we need this at all?
> + return true;
> + }
> +
> + return false;
> +}
--
With Best Regards,
Andy Shevchenko
