linux-kernel - Re: [PATCH v3 0/4] DT clock bindings

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Date:	Mon, 2 Jul 2012 18:30:22 -0700
From:	"Turquette, Mike" <mturquette@...com>
To:	Rob Herring <robherring2@...il.com>
Cc:	Chris Ball <cjb@...top.org>, Mitch Bradley <wmb@...top.org>,
	Arnd Bergmann <arnd@...db.de>,
	devicetree-discuss@...ts.ozlabs.org, sboyd@...eaurora.org,
	linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	skannan@...eaurora.org, Olof Johansson <olof@...om.net>,
	shawn.guo@...aro.org, s.hauer@...gutronix.de,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 0/4] DT clock bindings

On Wed, Jun 27, 2012 at 5:54 AM, Rob Herring <robherring2@...il.com> wrote:
> On 06/21/2012 12:54 PM, Mike Turquette wrote:
>> On 20120621-10:00, Rob Herring wrote:
>>> On 06/21/2012 02:27 AM, Chris Ball wrote:
>>>>
>>>> 2) Use alloc_bootmem() instead of kzalloc() in of_clk_add_provider(),
>>>>    because we need to set up clocks during .init_early on ARM (which
>>>>    happens pre-slab) so that they are available for platform init.
>>>
>>> This depends on 1 as the common clock code would have the same issue.
>>> Generally, the first place clocks are needed is the timer init. At that
>>> point, you can call kzalloc. This is where all the clock init used to be
>>> done until init_early was added and some platforms have moved their
>>> clock init. I don't think there was really ever much reason to move it
>>> other than to make the timer init function only deal with timer setup.
>>>
>>
>> Hi Rob,
>>
>> Just FYI I've been looking at using alloc_bootmem in the common clk code
>> as a way to get rid of the static initialization stuff (which only
>> existed due to very early initialization of timers).
>
> The slab is up at the time timers are initialized. The only real problem
> is mixing clock init into the timer init functions and clk init in
> init_early is cleaner in that regard.
>

Hi Rob,

I'm afraid I don't follow you when you say "slab is up at the time
timers are initialized".  On some platforms I believe that timer
initialization takes place before slab is ready (.early_init).

>> The suggested change above to of_clk_add_provider would jive well with
>> my change to the common clk code.
>
> Are you planning this for 3.6? If not, then this can be addressed at the
> time the clk framework supports bootmem.
>
> I'm not so sure more users of bootmem are desired. There seems to be
> some effort/desire to remove it:
>
> http://lists.linux-foundation.org/pipermail/ksummit-2012-discuss/2012-June/000562.html
> https://lkml.org/lkml/2012/3/13/586
> http://lists.infradead.org/pipermail/linux-arm-kernel/2011-December/074886.html

So after looking at those mails it seems using memblock_alloc would be
a better alternative.  Did I get that right?

Thanks,
Mike

>
> Rob
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