linux-kernel - Re: [PATCH v2 1/3] platform/x86: intel_scu_ipc: Check status after timeout in busy

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Message-ID: <CAE-0n53Tqcq8KHaYA8+1_kxy2nPmcRp3t1NK_vAZM=9tfCxqjA@mail.gmail.com>
Date:   Wed, 6 Sep 2023 15:23:56 -0500
From:   Stephen Boyd <swboyd@...omium.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        platform-driver-x86@...r.kernel.org,
        Prashant Malani <pmalani@...omium.org>
Subject: Re: [PATCH v2 1/3] platform/x86: intel_scu_ipc: Check status after
 timeout in busy_loop()

Quoting Kuppuswamy Sathyanarayanan (2023-09-06 13:20:49)
> On 9/6/2023 1:14 PM, Stephen Boyd wrote:
> > Quoting Andy Shevchenko (2023-09-06 13:04:54)
> >> On Wed, Sep 06, 2023 at 11:09:41AM -0700, Stephen Boyd wrote:
> >>>               status = ipc_read_status(scu);
> >>>               if (!(status & IPC_STATUS_BUSY))
> >>
> >>> -                     return (status & IPC_STATUS_ERR) ? -EIO : 0;
> >>> +                     goto not_busy;
> >>
> >> Wouldn't simple 'break' suffice here?
> >
> > Yes, at the cost of reading the status again when it isn't busy, or
> > checking the busy bit after the loop breaks out and reading it once
> > again when it is busy. I suppose the compiler would figure that out and
> > optimize so that break would simply goto the return statement.
> >
> > The code could look like this without a goto.
> >
> >       do {
> >               status = ipc_read_status(scu);
> >               if (!(status & IPC_STATUS_BUSY))
> >                       break;
> >       } while (time_before(jiffies, end));
> >
> >       if (status & IPC_STATUS_BUSY)
> >               status = ipc_read_status(scu);
>
> IMO, you can remove the if condition and read again the status in all cases.
> It is more readable. But it is up to you.
>

I don't really care either way. Just let me know what makes the
maintainers happy here.