linux-kernel - Re: [PATCH] clk: Make of_clk_get_parent

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Date:	Fri, 16 Oct 2015 05:55:33 -0700
From:	Michael Turquette <mturquette@...libre.com>
To:	Stephen Boyd <sboyd@...eaurora.org>,
	"Thomas Petazzoni" <thomas.petazzoni@...e-electrons.com>
Cc:	linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
	"Gregory CLEMENT <gregory.clement@...e-electrons.com>, Jason Cooper
	<jason@...edaemon.net>, Andrew Lunn <andrew@...n.ch>, Sebastian
	Hesselbarth" <sebastian.hesselbarth@...il.com>,
	geert@...ux-m68k.org, magnus.damm@...il.com
Subject: Re: [PATCH] clk: Make of_clk_get_parent_name() robust with #clock-cells = 1

Cc'ing Geert.

Quoting Stephen Boyd (2015-10-15 16:19:38)
> If a clock provider has #clock-cells = 1 and we call
> of_clk_get_parent_name() on it we may end up returning the name
> of the provider node if the provider doesn't have a
> clock-output-names property. This doesn't make sense, especially
> when you consider that calling of_clk_get_parent_name() on such a
> node with different indices will return the same name each time.
> 
> Let's try getting the clock from the framework via of_clk_get()
> instead, and only fallback to the node name if we have a provider
> with #clock-cells = 0. This way, we can't hand out the same name
> for different clocks when we don't actually know their names.
> 
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>

Geert,

Does this approach fix the issues you had removing clock-output-names
from your clock provider DTS?

Regards,
Mike

> ---
>  drivers/clk/clk.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index b005f666e3a1..a0fe9ca1f0af 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3055,6 +3055,7 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
>         u32 pv;
>         int rc;
>         int count;
> +       struct clk *clk;
>  
>         if (index < 0)
>                 return NULL;
> @@ -3080,8 +3081,25 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
>  
>         if (of_property_read_string_index(clkspec.np, "clock-output-names",
>                                           index,
> -                                         &clk_name) < 0)
> -               clk_name = clkspec.np->name;
> +                                         &clk_name) < 0) {
> +               /*
> +                * Best effort to get the name if the clock has been
> +                * registered with the framework. If the clock isn't
> +                * registered, we return the node name as the name of
> +                * the clock as long as #clock-cells = 0.
> +                */
> +               clk = of_clk_get_from_provider(&clkspec);
> +               if (IS_ERR(clk)) {
> +                       if (clkspec.args_count == 0)
> +                               clk_name = clkspec.np->name;
> +                       else
> +                               clk_name = NULL;
> +               } else {
> +                       clk_name = __clk_get_name(clk);
> +                       clk_put(clk);
> +               }
> +       }
> +
>  
>         of_node_put(clkspec.np);
>         return clk_name;
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 
--
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