linux-kernel - Re: [PATCH 3/3] cpufreq: ppc: Fix handling of non-existent clocks

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Date:	Mon, 21 Apr 2014 11:31:05 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Geert Uytterhoeven <geert+renesas@...der.be>,
	Mike Turquette <mike.turquette@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] cpufreq: ppc: Fix handling of non-existent clocks

On 17 April 2014 15:23, Geert Uytterhoeven <geert+renesas@...der.be> wrote:
> If the clock doesn't exist, clk_get_rate() returns -EINVAL

You clk_get_rate() isn't written well then, it should return zero.
@Mike: I didn't see this clearly mentioned in clk.h, should we fix
that?

>, which becomes
> a large number (freq is u32), failing the "freq < min_cpufreq" test.
> Explicitly test for "(u32)-EINVAL" to fix this.

That's a bad check. We should have done this instead:

(s32)freq < 0; but that would be true for high values of clock. And that's
why clk_get_rate() must return zero for errors.

> Update the comment, and fix a grammer issue while we're at it.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
>  drivers/cpufreq/ppc-corenet-cpufreq.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/cpufreq/ppc-corenet-cpufreq.c b/drivers/cpufreq/ppc-corenet-cpufreq.c
> index 53881d78a931..7027eab814ce 100644
> --- a/drivers/cpufreq/ppc-corenet-cpufreq.c
> +++ b/drivers/cpufreq/ppc-corenet-cpufreq.c
> @@ -179,10 +179,11 @@ static int corenet_cpufreq_cpu_init(struct cpufreq_policy *policy)
>                 clk = of_clk_get(data->parent, i);
>                 freq = clk_get_rate(clk);
>                 /*
> -                * the clock is valid if its frequency is not masked
> -                * and large than minimum allowed frequency.
> +                * the clock is valid if it exists, its frequency is not
> +                * masked, and larger than minimum allowed frequency.
>                  */
> -               if (freq < min_cpufreq || (mask & (1 << i)))
> +               if (freq == (u32)-EINVAL || freq < min_cpufreq ||
> +                   (mask & (1 << i)))
>                         table[i].frequency = CPUFREQ_ENTRY_INVALID;
>                 else
>                         table[i].frequency = freq / 1000;
> --
> 1.7.9.5
>
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