linux-kernel - Re: [PATCH V2 3/3] cpufreq: Tegra: implement intermediate frequency callbacks

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Message-ID: <53765E59.6090302@wwwdotorg.org>
Date:	Fri, 16 May 2014 12:52:09 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>, rjw@...ysocki.net
CC:	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, arvind.chauhan@....com,
	swarren@...dia.com, nicolas.pitre@...aro.org,
	dianders@...omium.org, linux@....linux.org.uk,
	thomas.abraham@...aro.org, pdeschrijver@...dia.com
Subject: Re: [PATCH V2 3/3] cpufreq: Tegra: implement intermediate frequency
 callbacks

On 05/16/2014 03:07 AM, Viresh Kumar 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.

> diff --git a/drivers/cpufreq/tegra-cpufreq.c b/drivers/cpufreq/tegra-cpufreq.c

> +static int
> +tegra_target_intermediate(struct cpufreq_policy *policy, unsigned int frequency)
> +{
> +	return clk_set_parent(cpu_clk, pll_p_clk);
> +}

I think you also need to move the following code from
tegra_cpu_clk_set_rate() to the start of tegra_target_intermediate().
Otherwise, pll_x will turn off, which judging by the comment in
tegra_cpu_clk_set_rate(), shouldn't be allowed to happen:

        /*
         * Take an extra reference to the main pll so it doesn't turn
         * off when we move the cpu off of it
         */
        clk_prepare_enable(pll_x_clk);

I'll go try this version anyway in a minute...
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