linux-kernel - Re: [PATCH V6 04/21] clk: tegra: Save and restore divider rate

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Message-ID: <88a6a8ea-df4e-4cdf-4723-6e16d645218c@gmail.com>
Date:   Mon, 22 Jul 2019 01:14:55 +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 04/21] clk: tegra: Save and restore divider rate

21.07.2019 22:40, Sowjanya Komatineni пишет:
> This patch implements context save and restore for clock divider.
> 
> During system suspend, core power goes off and looses the settings
> of the Tegra CAR controller registers.
> 
> So during suspend entry the context of clock divider is saved and
> on resume context is restored back for normal operation.
> 
> Acked-by: Thierry Reding <treding@...dia.com>
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/clk/tegra/clk-divider.c | 23 +++++++++++++++++++++++
>  drivers/clk/tegra/clk.h         |  2 ++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/drivers/clk/tegra/clk-divider.c b/drivers/clk/tegra/clk-divider.c
> index e76731fb7d69..ecb7ff9ce97e 100644
> --- a/drivers/clk/tegra/clk-divider.c
> +++ b/drivers/clk/tegra/clk-divider.c
> @@ -109,10 +109,33 @@ static int clk_frac_div_set_rate(struct clk_hw *hw, unsigned long rate,
>  	return 0;
>  }
>  
> +static int clk_divider_save_context(struct clk_hw *hw)
> +{
> +	struct tegra_clk_frac_div *divider = to_clk_frac_div(hw);
> +	struct clk_hw *parent = clk_hw_get_parent(hw);
> +	unsigned long parent_rate = clk_hw_get_rate(parent);
> +
> +	divider->rate = clk_frac_div_recalc_rate(hw, parent_rate);

I'm not sure what's the point of this, because clk_hw_get_rate() returns
cached value.

> +	return 0;
> +}
> +
> +static void clk_divider_restore_context(struct clk_hw *hw)
> +{
> +	struct tegra_clk_frac_div *divider = to_clk_frac_div(hw);
> +	struct clk_hw *parent = clk_hw_get_parent(hw);
> +	unsigned long parent_rate = clk_hw_get_rate(parent);
> +
> +	if (clk_frac_div_set_rate(hw, divider->rate, parent_rate) < 0)
> +		WARN_ON(1);

Hence this could be:

	unsigned long parent_rate = clk_hw_get_rate(parent);
	unsigned long rate = clk_hw_get_rate(hw);

	if (clk_frac_div_set_rate(hw, rate, parent_rate) < 0)
		WARN_ON(1);

> +}
> +
>  const struct clk_ops tegra_clk_frac_div_ops = {
>  	.recalc_rate = clk_frac_div_recalc_rate,
>  	.set_rate = clk_frac_div_set_rate,
>  	.round_rate = clk_frac_div_round_rate,
> +	.save_context = clk_divider_save_context,
> +	.restore_context = clk_divider_restore_context,
>  };
>  
>  struct clk *tegra_clk_register_divider(const char *name,
> diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
> index 905bf1096558..83623f5f55f3 100644
> --- a/drivers/clk/tegra/clk.h
> +++ b/drivers/clk/tegra/clk.h
> @@ -42,6 +42,7 @@ struct clk *tegra_clk_register_sync_source(const char *name,
>   * @width:	width of the divider bit field
>   * @frac_width:	width of the fractional bit field
>   * @lock:	register lock
> + * @rate:	rate during suspend and resume
>   *
>   * Flags:
>   * TEGRA_DIVIDER_ROUND_UP - This flags indicates to round up the divider value.
> @@ -62,6 +63,7 @@ struct tegra_clk_frac_div {
>  	u8		width;
>  	u8		frac_width;
>  	spinlock_t	*lock;
> +	unsigned long	rate;
>  };
>  
>  #define to_clk_frac_div(_hw) container_of(_hw, struct tegra_clk_frac_div, hw)
>