linux-kernel - Re: [PATCH V5 2/2] cpufreq: Tegra: implement intermediate frequency callbacks

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Date:	Thu, 5 Jun 2014 12:51:46 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arvind Chauhan <arvind.chauhan@....com>,
	Stephen Warren <swarren@...dia.com>,
	Russell King <linux@....linux.org.uk>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Thomas Abraham <thomas.abraham@...aro.org>,
	Peter De Schrijver <pdeschrijver@...dia.com>
Subject: Re: [PATCH V5 2/2] cpufreq: Tegra: implement intermediate frequency callbacks

Viresh,

On Mon, Jun 2, 2014 at 10:19 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> Tegra had always been switching to intermediate frequency (pll_p_clk) since
> ever. CPUFreq core has better support for handling notifications for these
> frequencies and so we can adapt Tegra's driver to it.
>
> Also do a WARN() if clk_set_parent() fails while moving back to pll_x as we
> should have atleast restored to earlier frequency on error.
>
> Tested-by: Stephen Warren <swarren@...dia.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/tegra-cpufreq.c | 97 ++++++++++++++++++++++++++---------------
>  1 file changed, 62 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/cpufreq/tegra-cpufreq.c b/drivers/cpufreq/tegra-cpufreq.c
> index 6e774c6..a5fbc0a 100644
> --- a/drivers/cpufreq/tegra-cpufreq.c
> +++ b/drivers/cpufreq/tegra-cpufreq.c
> @@ -45,46 +45,51 @@ static struct clk *cpu_clk;
>  static struct clk *pll_x_clk;
>  static struct clk *pll_p_clk;
>  static struct clk *emc_clk;
> +static bool pll_x_prepared;
>
> -static int tegra_cpu_clk_set_rate(unsigned long rate)
> +static unsigned int tegra_get_intermediate(struct cpufreq_policy *policy,
> +                                          unsigned int index)
> +{
> +       unsigned int ifreq = clk_get_rate(pll_p_clk) / 1000;
> +
> +       /*
> +        * Don't switch to intermediate freq if:
> +        * - we are already at it, i.e. policy->cur == ifreq
> +        * - index corresponds to ifreq
> +        */
> +       if ((freq_table[index].frequency == ifreq) || (policy->cur == ifreq))
> +               return 0;
> +
> +       return ifreq;
> +}
> +
> +static int tegra_target_intermediate(struct cpufreq_policy *policy,
> +                                    unsigned int index)
>  {
>         int ret;
>
>         /*
>          * Take an extra reference to the main pll so it doesn't turn
> -        * off when we move the cpu off of it
> +        * off when we move the cpu off of it as enabling it again while we
> +        * switch to it from tegra_target() would take additional time. Though
> +        * when target-freq is intermediate freq, we don't need to take this
> +        * reference.

The "Though when target-freq is intermediate freq, we don't need to
take this reference." makes me think that this function is actually
called when target-freq is intermediate freq.  I don't think it is,
right?

I don't think that's a huge deal, though and code wise this looks good to me.

Reviewed-by: Doug Anderson <dianders@...omium.org>
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