linux-kernel - Re: [PATCH v2] clk: Do not complain about correctly set read-only muxes when assigning clock parents from device tree

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Message-ID: <1420815016.3914.16.camel@pengutronix.de>
Date:	Fri, 09 Jan 2015 15:50:16 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Mike Turquette <mturquette@...aro.org>,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH v2] clk: Do not complain about correctly set read-only
 muxes when assigning clock parents from device tree

Hi Stephen,

Am Donnerstag, den 08.01.2015, 13:32 -0800 schrieb Stephen Boyd:
[...]
> Why not do this in the core? As far as I can tell other drivers could
> run into the same problem, no? Does this work?
> 
> -----8<-------
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index f4963b7d4e17..3278645f4729 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1677,16 +1677,18 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
>  	if (!clk)
>  		return 0;
>  
> -	/* verify ops for for multi-parent clks */
> -	if ((clk->num_parents > 1) && (!clk->ops->set_parent))
> -		return -ENOSYS;
> -
>  	/* prevent racing with updates to the clock topology */
>  	clk_prepare_lock();
>  
>  	if (clk->parent == parent)
>  		goto out;
>  
> +	/* verify ops for for multi-parent clks */
> +	if ((clk->num_parents > 1) && (!clk->ops->set_parent)) {
> +		ret = -ENOSYS;
> +		goto out;
> +	}
> +
>  	/* check that we are allowed to re-parent if the clock is in use */
>  	if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count) {
>  		ret = -EBUSY;

"[PATCH] clk: make set_parent succeed for any clock if the parent to be
set is the same as the current parent" ?

It works, but it also changes the API, as it makes
   clk_set_parent(some_non_mux, its_current_parent)
succeed instead of return -ENOSYS.

regards
Philipp

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