Re: [PATCH 1/3] platform/x86: intel_scu_ipc: Check status after timeouts in busy_loop()

[Stephen Boyd]

Quoting Mika Westerberg (2023-08-31 22:50:11)
> On Wed, Aug 30, 2023 at 06:14:01PM -0700, Stephen Boyd wrote:
> > It's possible for the polling loop in busy_loop() to get scheduled away
> > for a long time.
> >
> >   status = ipc_read_status(scu);
> >   <long time scheduled away>
> >   if (!(status & IPC_STATUS_BUSY))
>
> How can the status bit change here as we are the only user and the SCU
> access is serialized by ipclock?

I don't know how the SCU works. I thought that IPC_STATUS_BUSY bit was
cleared by the SCU when it was done processing. With that assumption, I
tried to show that the status is read and then the process schedules
away for a long time and has an outdated view of the busy bit.