linux-kernel - Re: [PATCH 3/4] clk: Provide always-on clock support

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Date:	Fri, 27 Feb 2015 21:51:20 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:	kernel@...inux.com, mturquette@...aro.org, sboyd@...eaurora.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH 3/4] clk: Provide always-on clock support

On Fri, 27 Feb 2015, Lee Jones wrote:

> Lots of platforms contain clocks which if turned off would prove fatal.
> The only way to recover from these catastrophic failures is to restart
> the board(s).  Now, when a clock is registered with the framework it is
> compared against a list of provided always-on clock names which must be
> kept ungated.  If it matches, we enable the existing CLK_IGNORE_UNUSED
> flag, which will prevent the common clk framework from attempting to
> gate it during the clk_disable_unused() procedure.
> 
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>  drivers/clk/clk.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 61c3fc5..3aab75e 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -2856,6 +2856,9 @@ int of_clk_add_provider(struct device_node *np,
>  			void *data)
>  {
>  	struct of_clk_provider *cp;
> +	struct property *prop;
> +	struct clk *clk;
> +	const char *clkname;
>  	int ret;
>  
>  	cp = kzalloc(sizeof(struct of_clk_provider), GFP_KERNEL);
> @@ -2875,6 +2878,14 @@ int of_clk_add_provider(struct device_node *np,
>  	if (ret < 0)
>  		of_clk_del_provider(np);
>  
> +	of_property_for_each_string(np, "clock-always-on", prop, clkname) {
> +		clk = __clk_lookup(clkname);
> +		if (!clk)
> +			continue;
> +
> +		clk->core->flags |= CLK_IGNORE_UNUSED;

Might save a few cycles by breaking here.

> +	}
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(of_clk_add_provider);

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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