linux-kernel - Re: [PATCH] clkdev: only fall through to clk_get

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Date:	Sun, 27 Apr 2014 16:37:06 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Russell King <rmk+kernel@....linux.org.uk>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH] clkdev: only fall through to clk_get_sys() if DT
 indicates no entry

On Sat, Apr 26, 2014 at 10:49 AM, Russell King
<rmk+kernel@....linux.org.uk> wrote:
> There are two failures which DT can return when looking up a phandle:
> -ENOENT - when DT finds that the desired property/index is not present
> -EINVAL - when DT finds that the desired property/index is present, but
>  there is a problem parsing it.
>
> We should only fall through to clk_get_sys() (the table driven clock
> lookup) when DT indicates that there was no entry in the OF tables
> for the clock.  Doing otherwise causes the clk API to always indicate
> that there is no entry for this clock, which is not correct behaviour.
>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
> ---
> Grant, Rob,
>
> Please let me know ASAP if this gives you any cause for concern.  This
> looks to me like a long standing bug which really needs fixing.  Part
> of the motivation here is similar to Jean-Francois' patch to clkdev
> which allows a DT specified clock which isn't get present to have
> clk_get() and friends return -EPROBE_DEFER - again, something that I
> think really should happen.  Jean-Francois hasn't been able to get
> much traction for his patch, so let's start with fixing this bug first.

I have no issues. A platform would have to be pretty broken to be
relying on the current behavior.

Rob

>
>  drivers/clk/clkdev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
> index 48f67218247c..4e65d0e10b05 100644
> --- a/drivers/clk/clkdev.c
> +++ b/drivers/clk/clkdev.c
> @@ -165,7 +165,7 @@ struct clk *clk_get(struct device *dev, const char *con_id)
>
>         if (dev) {
>                 clk = of_clk_get_by_name(dev->of_node, con_id);
> -               if (!IS_ERR(clk))
> +               if (!IS_ERR(clk) || PTR_ERR(clk) != -ENOENT)
>                         return clk;
>         }
>
> --
> 1.8.3.1
>
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