linux-kernel - Re: [PATCH v5 4/5] clk: add CLK_SET_RATE_NO

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Date:	Thu, 25 Jul 2013 14:34:14 +0200
From:	Sylwester Nawrocki <s.nawrocki@...sung.com>
To:	James Hogan <james.hogan@...tec.com>
Cc:	Mike Turquette <mturquette@...aro.org>,
	linux-arm-kernel@...ts.infradead.org,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-kernel@...r.kernel.org,
	Saravana Kannan <skannan@...eaurora.org>,
	Doug Anderson <dianders@...omium.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	Russell King <linux@....linux.org.uk>,
	Viresh Kumar <viresh.linux@...il.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	Chao Xie <xiechao.mail@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	Emilio López <emilio@...pez.com.ar>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Prashant Gaikwad <pgaikwad@...dia.com>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	Joseph Lo <josephl@...dia.com>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	Pawel Moll <pawel.moll@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH v5 4/5] clk: add CLK_SET_RATE_NO_REPARENT flag

Hi James,

On 06/13/2013 06:06 PM, James Hogan wrote:
> Add a CLK_SET_RATE_NO_REPARENT clock flag, which will prevent muxes
> being reparented during clk_set_rate.
> 
> To avoid breaking existing platforms, all callers of clk_register_mux()
> are adjusted to pass the new flag. Platform maintainers are encouraged
> to remove the flag if they wish to allow mux reparenting on set_rate.
[..]
> Changes in v3:
> 
> * rename/invert CLK_SET_RATE_REMUX to CLK_SET_RATE_NO_REPARENT and move
>   to this new patch.
> * patch 3: add CLK_SET_RATE_NO_REPARENT flag to all callers of
>   clk_register_mux. If you don't mind your clocks being reparented in
>   response to set_rate please let me know and I'll drop the relevant
>   portion of the patch.

Why is this better to change current behaviour of the clock core
and modify all drivers instead of having, e.g. CLK_SET_RATE_REPARENT
set in drivers of hardware that supports clock re-parenting while
setting clock rate ?

Is there intention to just have the automatic clock re-parenting
as a default feature in the common clock API ?
My apologies if this has already been answered, I haven't been
following this thread.

Thanks,
Sylwester

>  arch/arm/mach-imx/clk.h              |   5 +-
>  drivers/clk/mmp/clk-mmp2.c           |  39 +++++---
>  drivers/clk/mmp/clk-pxa168.c         |  40 +++++---
>  drivers/clk/mmp/clk-pxa910.c         |  31 +++---
>  drivers/clk/mxs/clk.h                |   4 +-
>  drivers/clk/samsung/clk.h            |   2 +-
>  drivers/clk/spear/spear1310_clock.c  | 179 ++++++++++++++++++-----------------
>  drivers/clk/spear/spear1340_clock.c  |  97 ++++++++++---------
>  drivers/clk/spear/spear3xx_clock.c   |  57 +++++++----
>  drivers/clk/spear/spear6xx_clock.c   |  35 +++----
>  drivers/clk/sunxi/clk-sunxi.c        |   3 +-
>  drivers/clk/tegra/clk-tegra114.c     |  36 ++++---
>  drivers/clk/tegra/clk-tegra20.c      |   6 +-
>  drivers/clk/tegra/clk-tegra30.c      |  33 ++++---
>  drivers/clk/versatile/clk-vexpress.c |   4 +-
>  include/linux/clk-provider.h         |   1 +
>  16 files changed, 334 insertions(+), 238 deletions(-)

-- 
Sylwester Nawrocki
Samsung R&D Institute Poland
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