linux-kernel - Re: [PATCH v7 06/20] clk: tegra: Support for OSC context save and restore

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Date:   Wed, 31 Jul 2019 14:11:02 +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 v7 06/20] clk: tegra: Support for OSC context save and
 restore

31.07.2019 3:20, Sowjanya Komatineni пишет:
> This patch adds support for saving OSC clock frequency and the
> drive-strength during OSC clock init and creates an API to restore
> OSC control register value from the saved context.
> 
> This API is invoked by Tegra210 clock driver during system resume
> to restore the  OSC clock settings.
> 
> Acked-by: Thierry Reding <treding@...dia.com>
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/clk/tegra/clk-tegra-fixed.c | 15 +++++++++++++++
>  drivers/clk/tegra/clk.h             |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/drivers/clk/tegra/clk-tegra-fixed.c b/drivers/clk/tegra/clk-tegra-fixed.c
> index 8d91b2b191cf..7c6c8abfcde6 100644
> --- a/drivers/clk/tegra/clk-tegra-fixed.c
> +++ b/drivers/clk/tegra/clk-tegra-fixed.c
> @@ -17,6 +17,10 @@
>  #define OSC_CTRL			0x50
>  #define OSC_CTRL_OSC_FREQ_SHIFT		28
>  #define OSC_CTRL_PLL_REF_DIV_SHIFT	26
> +#define OSC_CTRL_MASK			(0x3f2 |	\
> +					(0xf << OSC_CTRL_OSC_FREQ_SHIFT))
> +
> +static u32 osc_ctrl_ctx;
>  
>  int __init tegra_osc_clk_init(void __iomem *clk_base, struct tegra_clk *clks,
>  			      unsigned long *input_freqs, unsigned int num,
> @@ -29,6 +33,7 @@ int __init tegra_osc_clk_init(void __iomem *clk_base, struct tegra_clk *clks,
>  	unsigned osc_idx;
>  
>  	val = readl_relaxed(clk_base + OSC_CTRL);
> +	osc_ctrl_ctx = val & OSC_CTRL_MASK;
>  	osc_idx = val >> OSC_CTRL_OSC_FREQ_SHIFT;
>  
>  	if (osc_idx < num)
> @@ -96,3 +101,13 @@ void __init tegra_fixed_clk_init(struct tegra_clk *tegra_clks)
>  		*dt_clk = clk;
>  	}
>  }
> +
> +void tegra_clk_osc_resume(void __iomem *clk_base)
> +{
> +	u32 val;
> +
> +	val = readl_relaxed(clk_base + OSC_CTRL) & ~OSC_CTRL_MASK;
> +	val |= osc_ctrl_ctx;
> +	writel_relaxed(val, clk_base + OSC_CTRL);

Why a full raw u32 OSC_CTRL value couldn't be simply saved and restored?

> +	fence_udelay(2, clk_base);
> +}
> diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
> index f1ef6ae8c979..abba6d8a04cd 100644
> --- a/drivers/clk/tegra/clk.h
> +++ b/drivers/clk/tegra/clk.h
> @@ -842,6 +842,7 @@ u16 tegra_pll_get_fixed_mdiv(struct clk_hw *hw, unsigned long input_rate);
>  int tegra_pll_p_div_to_hw(struct tegra_clk_pll *pll, u8 p_div);
>  int div_frac_get(unsigned long rate, unsigned parent_rate, u8 width,
>  		 u8 frac_width, u8 flags);
> +void tegra_clk_osc_resume(void __iomem *clk_base);
>  
>  
>  /* Combined read fence with delay */
>