linux-kernel - Re: [PATCH v2 2/2] clk: prevent orphan clocks from being used

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Date:	Mon, 20 Apr 2015 15:32:46 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Heiko Stübner <heiko@...ech.de>,
	Mike Turquette <mturquette@...aro.org>
CC:	dianders@...omium.org, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	linux@....linux.org.uk
Subject: Re: [PATCH v2 2/2] clk: prevent orphan clocks from being used

On 04/12/15 04:38, Heiko Stübner wrote:
> Orphan clocks or children of orphan clocks don't have rate information at
> all and can produce strange results if they're allowed to be used and the
> parent becomes available later on.
>
> So using the newly introduced orphan status bit defer
> __of_clk_get_from_provider calls for orphan clocks.
>
> Signed-off-by: Heiko Stuebner <heiko@...ech.de>
> ---
>  drivers/clk/clk.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index a9fa5ab..b977701 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -2272,6 +2272,17 @@ bool clk_is_match(const struct clk *p, const struct clk *q)
>  }
>  EXPORT_SYMBOL_GPL(clk_is_match);
>  
> +static bool clk_is_orphan(const struct clk *clk)
> +{
> +	if (!clk)
> +		return false;
> +
> +	if (!clk->core)
> +		return false;

Looks like a useless check. clk->core better be there.

> +
> +	return clk->core->orphan;
> +}
> +
>  /**
>   * __clk_init - initialize the data structures in a struct clk
>   * @dev:	device initializing this clk, placeholder for now
> @@ -3009,6 +3020,11 @@ struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec,
>  		if (provider->node == clkspec->np)
>  			clk = provider->get(clkspec, provider->data);
>  		if (!IS_ERR(clk)) {
> +			if (clk_is_orphan(clk)) {
> +				clk = ERR_PTR(-EPROBE_DEFER);
> +				break;
> +			}
> +
>  			clk = __clk_create_clk(__clk_get_hw(clk), dev_id,
>  					       con_id);
>  

Otherwise looks good. We really need to test it on lots of platforms though.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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