linux-kernel - Re: [PATCH v8 12/21] cpufreq: tegra124: Add suspend and resume support

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Message-ID: <20190812100706.GK8903@ulmo>
Date:   Mon, 12 Aug 2019 12:07:06 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     jonathanh@...dia.com, tglx@...utronix.de, jason@...edaemon.net,
        marc.zyngier@....com, linus.walleij@...aro.org, stefan@...er.ch,
        mark.rutland@....com, pdeschrijver@...dia.com, pgaikwad@...dia.com,
        sboyd@...nel.org, linux-clk@...r.kernel.org,
        linux-gpio@...r.kernel.org, jckuo@...dia.com, josephl@...dia.com,
        talho@...dia.com, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, mperttunen@...dia.com,
        spatra@...dia.com, robh+dt@...nel.org, digetx@...il.com,
        devicetree@...r.kernel.org, rjw@...ysocki.net,
        viresh.kumar@...aro.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v8 12/21] cpufreq: tegra124: Add suspend and resume
 support

On Thu, Aug 08, 2019 at 04:46:51PM -0700, Sowjanya Komatineni wrote:
> This patch adds suspend and resume pm ops for cpufreq driver.
> 
> PLLP is the safe clock source for CPU during system suspend and
> resume as PLLP rate is below the CPU Fmax at Vmin.
> 
> CPUFreq driver suspend switches the CPU clock source to PLLP and
> disables the DFLL clock.
> 
> During system resume, warmboot code powers up the CPU with PLLP
> clock source. So CPUFreq driver resume enabled DFLL clock and
> switches CPU back to DFLL clock source.
> 
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> Reviewed-by: Dmitry Osipenko <digetx@...il.com>
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/cpufreq/tegra124-cpufreq.c | 60 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 60 insertions(+)
> 
> diff --git a/drivers/cpufreq/tegra124-cpufreq.c b/drivers/cpufreq/tegra124-cpufreq.c
> index 4f0c637b3b49..e979a3370988 100644
> --- a/drivers/cpufreq/tegra124-cpufreq.c
> +++ b/drivers/cpufreq/tegra124-cpufreq.c
> @@ -6,6 +6,7 @@
>  #define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
>  
>  #include <linux/clk.h>
> +#include <linux/cpufreq.h>
>  #include <linux/err.h>
>  #include <linux/init.h>
>  #include <linux/kernel.h>
> @@ -128,8 +129,67 @@ static int tegra124_cpufreq_probe(struct platform_device *pdev)
>  	return ret;
>  }
>  
> +static int __maybe_unused tegra124_cpufreq_suspend(struct device *dev)
> +{
> +	struct tegra124_cpufreq_priv *priv = dev_get_drvdata(dev);
> +	int err;
> +
> +	/*
> +	 * PLLP rate 408Mhz is below the CPU Fmax at Vmin and is safe to
> +	 * use during suspend and resume. So, switch the CPU clock source
> +	 * to PLLP and disable DFLL.
> +	 */
> +	err = clk_set_parent(priv->cpu_clk, priv->pllp_clk);
> +	if (err < 0) {
> +		dev_err(dev, "failed to reparent to PLLP: %d\n", err);
> +		return err;
> +	}
> +
> +	/* disable DFLL clock */
> +	clk_disable_unprepare(priv->dfll_clk);

This comment is superfluous since it doesn't explain anything that the
code below doesn't explain already.

Not sure who will end up merging this. If not me, then this is:

Acked-by: Thierry Reding <treding@...dia.com>

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