linux-kernel - Re: [PATCH] cpufreq: qcom-hw: Use optional irq API

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Message-ID: <CAE-0n53HNSRTdADO1dbQTyLafyajUTatMq5tsLeNDLQ4g95YpA@mail.gmail.com>
Date:   Wed, 17 Nov 2021 20:32:34 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH] cpufreq: qcom-hw: Use optional irq API

Quoting Thara Gopinath (2021-11-17 18:55:17)
> Hello Stephen,
>
> Thanks for the patch
>
> On 11/16/21 9:03 PM, Stephen Boyd wrote:
> > Use platform_get_irq_optional() to avoid a noisy error message when the
> > irq isn't specified. The irq is definitely optional given that we only
> > care about errors that are -EPROBE_DEFER here.
> >
> > Cc: Thara Gopinath <thara.gopinath@...aro.org>
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> > ---
> >   drivers/cpufreq/qcom-cpufreq-hw.c | 8 +++++---
> >   1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
> > index a2be0df7e174..b442d4983a22 100644
> > --- a/drivers/cpufreq/qcom-cpufreq-hw.c
> > +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
> > @@ -382,9 +382,11 @@ static int qcom_cpufreq_hw_lmh_init(struct cpufreq_policy *policy, int index)
> >        * Look for LMh interrupt. If no interrupt line is specified /
> >        * if there is an error, allow cpufreq to be enabled as usual.
> >        */
> > -     data->throttle_irq = platform_get_irq(pdev, index);
> > -     if (data->throttle_irq <= 0)
> > -             return data->throttle_irq == -EPROBE_DEFER ? -EPROBE_DEFER : 0;
> > +     data->throttle_irq = platform_get_irq_optional(pdev, index);
> > +     if (data->throttle_irq == -ENXIO)
> > +             return 0;
> > +     if (data->throttle_irq < 0)
> > +             return data->throttle_irq;
>
> Here the idea is to return only -EPROBE_DEFER error. Else return a 0 ,
> so that cpufreq is enabled even if lmh interrupt is inaccessible. The
> above check returns errors other than -EPROBE_DEFER as well. So I would
> say make irq optional and keep the below check
>
> if (data->throttle_irq <= 0)
>         return data->throttle_irq == -EPROBE_DEFER ? -EPROBE_DEFER : 0;

I'd like to catch other errors, for example, DT has an irq specified
that is outside the range of irqs available. If the DT is correct, then
it will either have a valid irq and this will return a >= 0 value or
nothing will be specified and we'll get back -ENXIO now. Do you have
some scenario where my patch fails to work?