linux-kernel - Re: [PATCH v10 2/3] clk: Make clk API return per-user struct clk instances

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Date:	Tue, 20 Jan 2015 16:14:15 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	linux-kernel@...r.kernel.org,
	Mike Turquette <mturquette@...aro.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Paul Walmsley <paul@...an.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v10 2/3] clk: Make clk API return per-user struct clk
 instances

On 01/20, Tomeu Vizoso wrote:
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 97f3425..e867d6a 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1719,6 +1817,31 @@ out:
>  
>  	return ret;
>  }
> +
> +/**
> + * clk_set_parent - switch the parent of a mux clk
> + * @clk: the mux clk whose input we are switching
> + * @parent: the new input to clk
> + *
> + * Re-parent clk to use parent as its new input source.  If clk is in
> + * prepared state, the clk will get enabled for the duration of this call. If
> + * that's not acceptable for a specific clk (Eg: the consumer can't handle
> + * that, the reparenting is glitchy in hardware, etc), use the
> + * CLK_SET_PARENT_GATE flag to allow reparenting only when clk is unprepared.
> + *
> + * After successfully changing clk's parent clk_set_parent will update the
> + * clk topology, sysfs topology and propagate rate recalculation via
> + * __clk_recalc_rates.
> + *
> + * Returns 0 on success, -EERROR otherwise.
> + */
> +int clk_set_parent(struct clk *clk, struct clk *parent)
> +{
> +	if (!clk || !parent)
> +		return 0;

This is a behavior change, although it's very possible nobody
cares besides clk.c itself. Before this change
clk_set_parent(clk, NULL) would orphan the clock and move it to
the orphan list. Now we're going to do nothing. We should keep
the original behavior, although I don't know why anybody would
want to orphan a clock from a driver. The only place I think
we're using this correctly is on the clock unregistration path.

> +
> +	return clk_core_set_parent(clk->core, parent->core);
> +}
>  EXPORT_SYMBOL_GPL(clk_set_parent);
>  
>  /**

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