linux-kernel - RE: [PATCH] ARM: imx: Add iram allocator functions

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Message-ID: <86A0E76937111F4C92FABEC0A2098851050F1387@az33exm21>
Date:	Tue, 5 Oct 2010 09:49:19 -0700
From:	Nguyen Dinh-R00091 <R00091@...escale.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
CC:	<linux-kernel@...r.kernel.org>, <amit.kucheria@...onical.com>,
	<s.hauer@...gutronix.de>, <grant.likely@...retlab.ca>,
	<valentin.longchamp@...l.ch>, <daniel@...aq.de>,
	Zhang Lily-R58066 <R58066@...escale.com>,
	<r.schwebel@...gutronix.de>,
	<linux-arm-kernel@...ts.infradead.org>, <kernel@...gutronix.de>
Subject: RE: [PATCH] ARM: imx: Add iram allocator functions



> -----Original Message-----
> From: Uwe Kleine-König [mailto:u.kleine-koenig@...gutronix.de]
> Sent: Tuesday, October 05, 2010 2:56 AM
> To: Nguyen Dinh-R00091
> Cc: linux-kernel@...r.kernel.org; amit.kucheria@...onical.com;
> s.hauer@...gutronix.de; grant.likely@...retlab.ca;
> valentin.longchamp@...l.ch; daniel@...aq.de; Zhang Lily-R58066;
> r.schwebel@...gutronix.de; linux-arm-kernel@...ts.infradead.org;
> kernel@...gutronix.de
> Subject: Re: [PATCH] ARM: imx: Add iram allocator functions
> 
> On Tue, Oct 05, 2010 at 09:44:23AM +0200, Uwe Kleine-König wrote:
> > On Mon, Oct 04, 2010 at 07:03:27PM -0500, Dinh.Nguyen@...escale.com
> wrote:
> > > From: Dinh Nguyen <Dinh.Nguyen@...escale.com>
> > >
> > > Add iram allocation functions using GENERIC_ALLOCATOR. The
> > > allocation size is 4KB multiples to guarantee alignment. The
> > > idea for these functions is for i.MX platforms to use them
> > > to dynamically allocate IRAM usage.
> > >
> > > Applies on 2.6.36-rc6
> > >
> > > Signed-off-by: Dinh Nguyen <Dinh.Nguyen@...escale.com>
> > > Reviewed-by: Amit Kucheria <amit.kucheria@...onical.com>
> > > ---
> > >  arch/arm/plat-mxc/Kconfig                   |   10 ++++
> > >  arch/arm/plat-mxc/Makefile                  |    1 +
> > >  arch/arm/plat-mxc/include/mach/iram_alloc.h |   35 +++++++++++++++
> > >  arch/arm/plat-mxc/iram.c                    |   62
> +++++++++++++++++++++++++++
> > >  4 files changed, 108 insertions(+), 0 deletions(-)
> > >  create mode 100644 arch/arm/plat-mxc/include/mach/iram_alloc.h
> > >  create mode 100644 arch/arm/plat-mxc/iram.c
> > >
> > > diff --git a/arch/arm/plat-mxc/Kconfig b/arch/arm/plat-mxc/Kconfig
> > > index 6785db4..5e4ff93 100644
> > > --- a/arch/arm/plat-mxc/Kconfig
> > > +++ b/arch/arm/plat-mxc/Kconfig
> > > @@ -57,6 +57,16 @@ source "arch/arm/mach-mx5/Kconfig"
> > >
> > >  endmenu
> > >
> > > +config IRAM_ALLOC
> > > +	bool "Enable IRAM allocator"
> > > +	default y
> > The iram allocator isn't useful taken alone, no?  So I suggest to make
> > it
> Hmm.  It seems I forgot to finish this sentence, sorry.
> 
> Unless IRAM_ALLOC is an optional feature for new features to come I'd
> not make it user selectible, but let the new features select IRAM_ALLOC.
> If it's optional I wonder if "default y" should really be done.
> 
> Maybe better call the symbol just IRAM?

IRAM should be in almost all SoCs, but it will be dependent on various drivers to make use of the IRAM. I think not making it user selectable and add IRAM_ALLOC to defconfigs where IRAM_ALLOC is needed makes sense. For example, the reason I am adding IRAM_ALLOC is to support MX51 suspend code. The MX51 suspend code needs to be run from IRAM. I think also IRAM_ALLOC is more descriptive symbol.

> 
> > > +	iram_pool = gen_pool_create(12, -1);
> > 	if (!iram_pool)
> > 		...
> After rereading the commit log I wondered where the 4 KB are enforced.
> Maybe do
> 
> 	s/12/PAGE_SHIFT/
> 
> to make it more obvious?

I'm unclear about your comment. Should I add a comment of something like this?
/* 12^2 will create a 4KB granularity. */

> 
> Best regards
> Uwe
> 
> --
> Pengutronix e.K.                           | Uwe Kleine-König
> |
> Industrial Linux Solutions                 | http://www.pengutronix.de/
> |


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