linux-kernel - Re: [PATCH 3/4] clk: add CLK_DEFER_ORPHAN flag to prevent orphans from being used

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Date:	Fri, 10 Apr 2015 17:52:43 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Heiko Stuebner <heiko@...ech.de>, mturquette@...aro.org
CC:	linux@....linux.org.uk, linux-kernel@...r.kernel.org,
	dianders@...omium.org, linux-rockchip@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/4] clk: add CLK_DEFER_ORPHAN flag to prevent orphans
 from being used

On 04/02/15 08:34, Heiko Stuebner wrote:
> The usage of clocks derived from an orphan can produce issues when trying
> to set rates etc. So ideally a clk_get to such a clock should defer till
> the clock hierarchy is complete.
> But as some arches probably rely on such clocks we can't disable them all.
> Therefore add a new clk flag where arches can enable this behaviour for
> their clocks.
>
> Signed-off-by: Heiko Stuebner <heiko@...ech.de>
> ---
>  drivers/clk/clk.c            | 6 ++++++
>  include/linux/clk-provider.h | 1 +
>  2 files changed, 7 insertions(+)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 476f491..8511c62 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3041,6 +3041,12 @@ 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_get_flags(clk) & CLK_DEFER_ORPHAN)
> +						&& clk_is_orphan(clk)) {
> +				clk = ERR_PTR(-EPROBE_DEFER);
> +				break;
> +			}
> +
>  			clk = __clk_create_clk(__clk_get_hw(clk), dev_id,
>  					       con_id);
>  
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 28abf1b..ef8d669 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -31,6 +31,7 @@
>  #define CLK_GET_RATE_NOCACHE	BIT(6) /* do not use the cached clk rate */
>  #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate change */
>  #define CLK_GET_ACCURACY_NOCACHE BIT(8) /* do not use the cached clk accuracy */
> +#define CLK_DEFER_ORPHAN	BIT(9) /* defer clk_get calls for orphans */
>  

I don't see why this is an opt-in feature. If we think there are arches
that are setting rates of clocks before they're ready then we have a
problem and we should fix it. These last two patches don't look necessary.

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

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