linux-kernel - Re: [PATCH v6 3/4] clk: Provide always-on clock support

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Message-ID: <20150408050257.GA31970@codeaurora.org>
Date:	Tue, 7 Apr 2015 22:02:57 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel@...inux.com, mturquette@...aro.org,
	devicetree@...r.kernel.org, geert@...ux-m68k.org
Subject: Re: [PATCH v6 3/4] clk: Provide always-on clock support

On 04/07, 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 provider is registered with the
> framework it is possible for a list of always-on clocks to be supplied
> which must be kept ungated.  Each clock mentioned in the newly
> introduced 'clock-always-on' will be clk_prepare_enable()d where the
> normal references will be taken.  This will prevent the common clk
> framework from attempting to gate them during the clk_disable_unused()
> and disable_clock() procedures.
> 
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>  drivers/clk/clk-conf.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c
> index aad4796..a07aced 100644
> --- a/drivers/clk/clk-conf.c
> +++ b/drivers/clk/clk-conf.c
> @@ -116,6 +116,43 @@ static int __set_clk_rates(struct device_node *node, bool clk_supplier)
>  	return 0;
>  }
>  
> +static int __set_clk_always_on(struct device_node *node, bool clk_supplier)
> +{
> +	struct of_phandle_args clkspec;
> +	struct clk *clk;
> +	struct property	*prop;
> +	const __be32 *cur;
> +	uint32_t index;

u32 please

> +	int ret;
> +
> +	if (!clk_supplier)
> +		return 0;
> +
> +	of_property_for_each_u32(node, "clock-always-on", prop, cur, index) {
> +		clkspec.np = node;
> +		clkspec.args_count = 1;
> +		clkspec.args[0] = index;
> +
> +		clk = of_clk_get_from_provider(&clkspec);
> +		if (IS_ERR(clk)) {
> +			pr_err("clk: couldn't get clock %u for %s\n",
> +				index, node->full_name);
> +			return PTR_ERR(clk);
> +		}
> +
> +		ret = clk_prepare_enable(clk);
> +		if (ret) {
> +			pr_err("Failed to enable clock %u for %s: %d\n",
> +			       index, node->full_name, ret);
> +			return ret;
> +		}

I guess we don't have a clk_put() here because we want to keep the
refcount high forever? We should at least put a comment here
explaining why we left out clk_put() if so.

> +
> +		pr_debug("Setting clock as always-on %pC\n", clk);
> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * of_clk_set_defaults() - parse and set assigned clocks configuration
>   * @node: device node to apply clock settings for

-- 
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