linux-kernel - Re: [PATCH 10/13] cpufreq: powernow-k8: Make use of known set but not used variables

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Message-ID: <20200714210135.GG1398296@dell>
Date:   Tue, 14 Jul 2020 22:01:35 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Andreas Herrmann <herrmann.der.user@...glemail.com>,
        Dominik Brodowski <linux@...do.de>,
        Pavel Machek <pavel@....cz>,
        Paul Devriendt <paul.devriendt@....com>,
        Mark Langsdorf <mark.langsdorf@....com>
Subject: Re: [PATCH 10/13] cpufreq: powernow-k8: Make use of known set but
 not used variables

On Tue, 14 Jul 2020, Rafael J. Wysocki wrote:

> On Tue, Jul 14, 2020 at 4:51 PM Lee Jones <lee.jones@...aro.org> wrote:
> >
> > If we fail to use a variable, even a 'dummy' one, then the compiler
> > complains that it is set but not used.  We know this is fine, so we
> > set it to its own value here.
> >
> > Fixes the following W=1 kernel build warning(s):
> >
> >  drivers/cpufreq/powernow-k8.c: In function ‘pending_bit_stuck’:
> >  drivers/cpufreq/powernow-k8.c:89:10: warning: variable ‘hi’ set but not used [-Wunused-but-set-variable]
> >  89 | u32 lo, hi;
> >  | ^~
> >  drivers/cpufreq/powernow-k8.c: In function ‘core_voltage_pre_transition’:
> >  drivers/cpufreq/powernow-k8.c:285:14: warning: variable ‘lo’ set but not used [-Wunused-but-set-variable]
> >  285 | u32 maxvid, lo, rvomult = 1;
> >  | ^~
> >
> > Cc: Andreas Herrmann <herrmann.der.user@...glemail.com>
> > Cc: Dominik Brodowski <linux@...do.de>
> > Cc: Pavel Machek <pavel@....cz>
> > Cc: Paul Devriendt <paul.devriendt@....com>
> > Cc: Mark Langsdorf <mark.langsdorf@....com>
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > ---
> >  drivers/cpufreq/powernow-k8.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
> > index 3984959eed1d5..b76df81044c4f 100644
> > --- a/drivers/cpufreq/powernow-k8.c
> > +++ b/drivers/cpufreq/powernow-k8.c
> > @@ -89,6 +89,7 @@ static int pending_bit_stuck(void)
> >         u32 lo, hi;
> >
> >         rdmsr(MSR_FIDVID_STATUS, lo, hi);
> > +       hi &= hi; /* Silence set but not used warning */
> 
> Hmm.
> 
> What about using __always_unused for this?

I didn't know you could use that for standard variables.

Will fix.

> >         return lo & MSR_S_LO_CHANGE_PENDING ? 1 : 0;
> >  }
> >
> > @@ -292,6 +293,7 @@ static int core_voltage_pre_transition(struct powernow_k8_data *data,
> >                 rvomult = 2;
> >         rvosteps *= rvomult;
> >         rdmsr(MSR_FIDVID_STATUS, lo, maxvid);
> > +       lo &= lo; /* Silence set but not used warning */
> >         maxvid = 0x1f & (maxvid >> 16);
> >         pr_debug("ph1 maxvid=0x%x\n", maxvid);
> >         if (reqvid < maxvid) /* lower numbers are higher voltages */
> >

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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