linux-kernel - Re: [PATCH v2 4/7] clk: Add simple gated clock

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Date:	Mon, 17 Oct 2011 10:46:45 -0700
From:	"Turquette, Mike" <mturquette@...com>
To:	Richard Zhao <richard.zhao@...aro.org>
Cc:	Sascha Hauer <s.hauer@...gutronix.de>, linaro-dev@...ts.linaro.org,
	eric.miao@...aro.org, grant.likely@...retlab.ca,
	Jamie Iles <jamie@...ieiles.com>, jeremy.kerr@...onical.com,
	sboyd@...inc.com, linux@....linux.org.uk, magnus.damm@...il.com,
	dsaxena@...aro.org, shawn.guo@...escale.com,
	arnd.bergmann@...aro.org, patches@...aro.org, tglx@...utronix.de,
	linux-arm-kernel@...ts.infradead.org, paul@...an.com,
	linus.walleij@...ricsson.com, broonie@...nsource.wolfsonmicro.com,
	linux-kernel@...r.kernel.org, amit.kucheria@...aro.org,
	Richard Zhao <richard.zhao@...escale.com>, skannan@...cinc.com
Subject: Re: [PATCH v2 4/7] clk: Add simple gated clock

On Sun, Oct 16, 2011 at 11:42 PM, Richard Zhao <richard.zhao@...aro.org> wrote:
> On Sun, Oct 16, 2011 at 08:26:49PM +0200, Sascha Hauer wrote:
>> On Wed, Oct 12, 2011 at 07:59:19AM -0700, Turquette, Mike wrote:
>> > On Tue, Oct 11, 2011 at 11:46 PM, Richard Zhao
>> > <richard.zhao@...escale.com> wrote:
>> > > On Thu, Sep 22, 2011 at 03:26:59PM -0700, Mike Turquette wrote:
>> > >> From: Jeremy Kerr <jeremy.kerr@...onical.com>
>> > >>
>> > >> Signed-off-by: Jeremy Kerr <jeremy.kerr@...onical.com>
>> > >> Signed-off-by: Mark Brown <broonie@...nsource.wolfsonmicro.com>
>> > >> Signed-off-by: Jamie Iles <jamie@...ieiles.com>
>> > >> Signed-off-by: Mike Turquette <mturquette@...com>
>> > >> ---
>> > >> Changes since v1:
>> > >> Add copyright header
>> > >> Fold in Jamie's patch for set-to-disable clks
>> > >> Use BIT macro instead of shift
>> > >>
>> > >>  drivers/clk/Kconfig    |    4 ++
>> > >>  drivers/clk/Makefile   |    1 +
>> > >>  drivers/clk/clk-gate.c |   78 ++++++++++++++++++++++++++++++++++++++++++++++++
>> > >>  include/linux/clk.h    |   13 ++++++++
>> > >>  4 files changed, 96 insertions(+), 0 deletions(-)
>> > >>  create mode 100644 drivers/clk/clk-gate.c
>> > >
>> > > I feel hard to tell the tree the clk parent, at register/init time. For the
>> > > simple gate clk, the only way is to set .get_parent. But normally, for clk
>> > > without any divider we set .get_parent to NULL. Maybe we can put .parent to
>> > > struct clk_hw?
>> >
>> > For non-mux clocks, whose parent is *always* going to be the same, you
>> > should create a duplicate .parent in the clk_hw_* structure and then
>> > have .get_parent return clk_hw_*->parent.
>>
>> Maybe I do not understand what you mean here, but I think there is
>> something missing in the gate.
> yes, clk_gate can not set fixed parent in v2 patch. Mike means add .parent int clk_gate
> and set .get_parent in the ops.

Yes, it seems I was unclear.  I mean to say that a .parent can be
added to any clk hw implementation (clk_hw_imx or whatever) and the
paired .ops (in this case, .get_parent) will know about it's
existence.

Regards,
Mike

>>
>> >
>> > This is analogous to the way clk_hw_fixed returns clk_hw_fixed->rate
>> > when .recalc is called on it.
>> >
>> > >> +
>> > >> +static unsigned long clk_gate_get_rate(struct clk_hw *clk)
>> > >> +{
>> > >> +     return clk_get_rate(clk_get_parent(clk->clk));
>> > >> +}
>>
>> clk_get_parent goes down to clk_gate_set_enable_ops.get_parent below...
>>
>> > >> +
>> > >> +
>> > >> +struct clk_hw_ops clk_gate_set_enable_ops = {
>> > >> +     .recalc_rate = clk_gate_get_rate,
>> > >> +     .enable = clk_gate_enable_set,
>> > >> +     .disable = clk_gate_disable_clear,
>> > >> +};
>>
>> ...but this does not have a get_parent pointer, so clk_get_parent()
>> for a gate always returns NULL which means that a gate never has
>> a valid rate.
>>
>> Sascha
>>
>> --
>> Pengutronix e.K.                           |                             |
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>
>
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