linux-kernel - Re: [RFC] clk: Make clk API return per-user struct clk instances

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Date:	Mon, 29 Sep 2014 18:40:23 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Mike Turquette <mturquette@...aro.org>,
	Russell King <linux@....linux.org.uk>
CC:	linux-kernel@...r.kernel.org,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Subject: Re: [RFC] clk: Make clk API return per-user struct clk instances

On 09/29/14 11:17, Tomeu Vizoso wrote:
> Also moves clock state to struct clk_core, but takes care to change as little
> API as possible.
>
> struct clk_hw still has a pointer to a struct clk, which is the
> implementation's per-user clk instance, for backwards compatibility.
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>
> ---
>
> Hello,
>
> I'm sending this alternate implementation of the switch to per-user clocks,
> with the added goal of not requiring any substantial changes to existing users
> of the API.
>
> This is pretty much RFC-quality right now, having only tested that it builds on
> tegra_defconfig.
>
> My main question right now is what do we want to do with those drivers that
> statically declare clocks. State is now in struct clk_core, so updating the
> drivers accordingly will amount to a substantial amount of lines changed, which
> we are now trying to avoid.

Who's actually using the static clocks? Isn't it just omap2? It looks
like all of those are behind the DEFINE_CLK define so changing it in
clk-private.h should "just work". I'm lost as to why static clocks are
being used there though. If it was a problem with allocating memory too
early it doesn't seem to be the case given that sometimes the .parents
field isn't set for a mux and __clk_init() will go and allocate an array
of pointers. Maybe I missed something though.

>
> Thanks,
>
> Tomeu
> ---
>  drivers/clk/clk-composite.c  |  12 +-
>  drivers/clk/clk.c            | 573 +++++++++++++++++++++++++++----------------
>  drivers/clk/clk.h            |   5 +
>  drivers/clk/clkdev.c         |  20 +-
>  drivers/clk/tegra/clk.c      |   2 +-
>  include/linux/clk-private.h  |  20 +-
>  include/linux/clk-provider.h |  22 +-
>  include/linux/clkdev.h       |   2 +-
>  8 files changed, 410 insertions(+), 246 deletions(-)
>
> diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c
> index b9355da..cb4a09d 100644
> --- a/drivers/clk/clk-composite.c
> +++ b/drivers/clk/clk-composite.c
> @@ -57,14 +57,14 @@ static unsigned long clk_composite_recalc_rate(struct clk_hw *hw,
>  
>  static long clk_composite_determine_rate(struct clk_hw *hw, unsigned long rate,
>  					unsigned long *best_parent_rate,
> -					struct clk **best_parent_p)
> +					struct clk_core **best_parent_p)


We should avoid exposing clk_core to anything besides clk.c or users of
clk-private.h (the latter which should go away once we remove all static
clocks).

-- 
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