linux-kernel - Re: [PATCH V6 11/21] clk: tegra: clk-dfll: Add suspend and resume support

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Date:   Mon, 22 Jul 2019 00:32:23 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, tglx@...utronix.de,
        jason@...edaemon.net, marc.zyngier@....com,
        linus.walleij@...aro.org, stefan@...er.ch, mark.rutland@....com
Cc:     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,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V6 11/21] clk: tegra: clk-dfll: Add suspend and resume
 support

21.07.2019 22:40, Sowjanya Komatineni пишет:
> This patch implements DFLL suspend and resume operation.
> 
> During system suspend entry, CPU clock will switch CPU to safe
> clock source of PLLP and disables DFLL clock output.
> 
> DFLL driver suspend confirms DFLL disable state and errors out on
> being active.
> 
> DFLL is re-initialized during the DFLL driver resume as it goes
> through complete reset during suspend entry.
> 
> Acked-by: Thierry Reding <treding@...dia.com>
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/clk/tegra/clk-dfll.c               | 44 ++++++++++++++++++++++++++++++
>  drivers/clk/tegra/clk-dfll.h               |  2 ++
>  drivers/clk/tegra/clk-tegra124-dfll-fcpu.c |  1 +
>  3 files changed, 47 insertions(+)
> 
> diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c
> index f8688c2ddf1a..7dcad4ccd0ae 100644
> --- a/drivers/clk/tegra/clk-dfll.c
> +++ b/drivers/clk/tegra/clk-dfll.c
> @@ -1513,6 +1513,50 @@ static int dfll_init(struct tegra_dfll *td)
>  	return ret;
>  }
>  
> +/**
> + * tegra_dfll_suspend - check DFLL is disabled
> + * @dev: DFLL device *
> + *
> + * DFLL clock should be disabled by the CPUFreq driver. So, make
> + * sure it is disabled and disable all clocks needed by the DFLL.
> + */
> +int tegra_dfll_suspend(struct device *dev)
> +{
> +	struct tegra_dfll *td = dev_get_drvdata(dev);
> +
> +	if (dfll_is_running(td)) {
> +		dev_warn(td->dev, "failed disabling the dfll\n");

Something like "dfll is enabled while shouldn't be\n" will be more
informative.

This is a error, hence dev_err().

> +		return -EBUSY;
> +	}
> +
> +	pm_runtime_disable(dev);
> +
> +	clk_unprepare(td->ref_clk);
> +	clk_unprepare(td->soc_clk);
> +	clk_unprepare(td->i2c_clk);

Please don't do this, DFLL is already disabled if not running.

> +	reset_control_assert(td->dvco_rst);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(tegra_dfll_suspend);
> +
> +/**
> + * tegra_dfll_resume - reinitialize DFLL on resume
> + * @pdev: DFLL instance
> + *
> + * Re-initialize DFLL on resume as it gets disabled and reset during
> + * suspend entry. DFLL clock is enabled in closed loop mode later
> + * and CPU frequency will be switched to DFLL output.
> + */
> +int tegra_dfll_resume(struct device *dev)
> +{
> +	struct tegra_dfll *td = dev_get_drvdata(dev);
> +
> +	return dfll_init(td);

Just create dfll_reinit() variant.

> +}
> +EXPORT_SYMBOL(tegra_dfll_resume);
> +
>  /*
>   * DT data fetch
>   */
> diff --git a/drivers/clk/tegra/clk-dfll.h b/drivers/clk/tegra/clk-dfll.h
> index 1b14ebe7268b..fb209eb5f365 100644
> --- a/drivers/clk/tegra/clk-dfll.h
> +++ b/drivers/clk/tegra/clk-dfll.h
> @@ -42,5 +42,7 @@ int tegra_dfll_register(struct platform_device *pdev,
>  struct tegra_dfll_soc_data *tegra_dfll_unregister(struct platform_device *pdev);
>  int tegra_dfll_runtime_suspend(struct device *dev);
>  int tegra_dfll_runtime_resume(struct device *dev);
> +int tegra_dfll_suspend(struct device *dev);
> +int tegra_dfll_resume(struct device *dev);
>  
>  #endif /* __DRIVERS_CLK_TEGRA_CLK_DFLL_H */
> diff --git a/drivers/clk/tegra/clk-tegra124-dfll-fcpu.c b/drivers/clk/tegra/clk-tegra124-dfll-fcpu.c
> index e84b6d52cbbd..2ac2679d696d 100644
> --- a/drivers/clk/tegra/clk-tegra124-dfll-fcpu.c
> +++ b/drivers/clk/tegra/clk-tegra124-dfll-fcpu.c
> @@ -631,6 +631,7 @@ static int tegra124_dfll_fcpu_remove(struct platform_device *pdev)
>  static const struct dev_pm_ops tegra124_dfll_pm_ops = {
>  	SET_RUNTIME_PM_OPS(tegra_dfll_runtime_suspend,
>  			   tegra_dfll_runtime_resume, NULL)
> +	SET_SYSTEM_SLEEP_PM_OPS(tegra_dfll_suspend, tegra_dfll_resume)
>  };
>  
>  static struct platform_driver tegra124_dfll_fcpu_driver = {
>