linux-kernel - Re: [PATCH 03/12] ARM: normalize clk API for older platforms

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Date:   Fri, 21 Jul 2017 13:35:51 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     Arnd Bergmann <arnd@...db.de>, Kevin Hilman <khilman@...nel.org>,
        Hartley Sweeten <hsweeten@...ionengravers.com>,
        Alexander Sverdlin <alexander.sverdlin@...il.com>,
        Eric Miao <eric.y.miao@...il.com>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Wan ZongShun <mcuos.com@...il.com>
CC:     <linux-clk@...r.kernel.org>, Stephen Boyd <sboyd@...eaurora.org>,
        Michael Turquette <mturquette@...libre.com>,
        Russell King <linux@...linux.org.uk>,
        Alexandre Bailon <abailon@...libre.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/12] ARM: normalize clk API for older platforms

Hi Arnd,

On Thursday 20 July 2017 09:20 PM, Arnd Bergmann wrote:
> Six ARM platforms still provide their own variant of the clk API
> rather than using the generic COMMON_CLK API. This generally works,
> but it causes some link errors with drivers using the clk_set_rate,
> clk_get_parent, clk_set_parent or clk_round_rate functions when
> a platform lacks those interfaces.
> 
> OMAP1 implements the whole set already, but davinci, ep93xx, mmp,
> sa1100 and w90x900 all lack at least one of the functions.
> 
> This adds empty stub implementations for each of them, and I
> don't even try to do something useful here but instead just
> print a WARN() message to make it obvious what is going on
> if they ever end up being called.
> 
> The drivers that call these won't be used on these platforms
> (otherwise we'd get a link error today), so the added code is harmless
> bloat and will warn about accidental use.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/arm/mach-davinci/clock.c |  6 ++++++
>  arch/arm/mach-ep93xx/clock.c  | 21 +++++++++++++++++++++
>  arch/arm/mach-mmp/clock.c     | 22 ++++++++++++++++++++++
>  arch/arm/mach-sa1100/clock.c  | 29 +++++++++++++++++++++++++++++
>  arch/arm/mach-w90x900/clock.c | 29 +++++++++++++++++++++++++++++
>  5 files changed, 107 insertions(+)
> 
> diff --git a/arch/arm/mach-davinci/clock.c b/arch/arm/mach-davinci/clock.c
> index f5dce9b4e617..89586779526c 100644
> --- a/arch/arm/mach-davinci/clock.c
> +++ b/arch/arm/mach-davinci/clock.c
> @@ -218,6 +218,12 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
>  }
>  EXPORT_SYMBOL(clk_set_parent);
>  
> +struct clk *clk_get_parent(struct clk *clk)
> +{
> +	return clk->parent;
> +}
> +EXPORT_SYMBOL(clk_get_parent);

For mach-davinci change:

Acked-by: Sekhar Nori <nsekhar@...com>

> +
>  int clk_register(struct clk *clk)
>  {
>  	if (clk == NULL || IS_ERR(clk))
> diff --git a/arch/arm/mach-ep93xx/clock.c b/arch/arm/mach-ep93xx/clock.c
> index 39ef3b613912..c1c91fc6e178 100644
> --- a/arch/arm/mach-ep93xx/clock.c
> +++ b/arch/arm/mach-ep93xx/clock.c
> @@ -323,6 +323,27 @@ unsigned long clk_get_rate(struct clk *clk)
>  }
>  EXPORT_SYMBOL(clk_get_rate);
>  
> +long clk_round_rate(struct clk *clk, unsigned long rate)
> +{
> +	WARN_ON(clk);
> +	return 0;
> +}
> +EXPORT_SYMBOL(clk_round_rate);

Its probably better to WARN_ON_ONCE(). Also, since NULL clk is valid, it
should be probably be WARN_ON_ONCE(1).

Thanks,
Sekhar