linux-kernel - Re: [PATCH v3 4/4] OMAP3/4: iommu: adapt to runtime pm

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Date:	Wed, 2 Nov 2011 10:22:04 -0500
From:	"Ramirez Luna, Omar" <omar.ramirez@...com>
To:	MyungJoo Ham <myungjoo.ham@...il.com>
Cc:	Tony Lindgren <tony@...mide.com>,
	Benoit Cousson <b-cousson@...com>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Russell King <linux@....linux.org.uk>,
	lkml <linux-kernel@...r.kernel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	lo <linux-omap@...r.kernel.org>,
	lak <linux-arm-kernel@...ts.infradead.org>,
	lm <linux-media@...r.kernel.org>,
	"Roedel, Joerg" <Joerg.Roedel@....com>,
	iommu@...ts.linux-foundation.org
Subject: Re: [PATCH v3 4/4] OMAP3/4: iommu: adapt to runtime pm

Hi MyungJoo,

On Wed, Nov 2, 2011 at 5:16 AM, MyungJoo Ham <myungjoo.ham@...il.com> wrote:
> On Wed, Nov 2, 2011 at 7:15 AM, Omar Ramirez Luna <omar.ramirez@...com> wrote:
>> Use runtime PM functionality interfaced with hwmod enable/idle
>> functions, to replace direct clock operations, reset and sysconfig
>> handling.
>>
>> Tidspbridge uses a macro removed with this patch, for now the value
>> is hardcoded to avoid breaking compilation.
>>
>> Signed-off-by: Omar Ramirez Luna <omar.ramirez@...com>
>> ---
>>  arch/arm/mach-omap2/iommu2.c                      |   17 --------
>>  arch/arm/mach-omap2/omap-iommu.c                  |    1 -
>>  arch/arm/plat-omap/include/plat/iommu.h           |    2 -
>>  arch/arm/plat-omap/include/plat/iommu2.h          |    2 -
>>  drivers/iommu/omap-iommu.c                        |   46 ++++++++-------------
>>  drivers/staging/tidspbridge/core/tiomap3430_pwr.c |    2 +-
>>  6 files changed, 19 insertions(+), 51 deletions(-)
>>
>> diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
>> index bbbf747..3c55be0 100644
>> --- a/drivers/iommu/omap-iommu.c
>> +++ b/drivers/iommu/omap-iommu.c
>> @@ -123,11 +123,11 @@ static int iommu_enable(struct omap_iommu *obj)
>>        if (!arch_iommu)
>>                return -ENODEV;
>>
>> -       clk_enable(obj->clk);
>> +       pm_runtime_enable(obj->dev);
>> +       pm_runtime_get_sync(obj->dev);
>>
>>        err = arch_iommu->enable(obj);
>>
>> -       clk_disable(obj->clk);
>>        return err;
>>  }
>>
>> @@ -136,11 +136,10 @@ static void iommu_disable(struct omap_iommu *obj)
>>        if (!obj)
>>                return;
>>
>> -       clk_enable(obj->clk);
>> -
>>        arch_iommu->disable(obj);
>>
>> -       clk_disable(obj->clk);
>> +       pm_runtime_put_sync(obj->dev);
>> +       pm_runtime_disable(obj->dev);
>>  }
> I'm just curious here... Is there any reason to do
> pm_runtime_enable/disable at iommu_enable/iommu_disable which are
> called by iommu_attach/detach?
> I thought that normally, ideal locations of pm_runtime_enable/disable
> for such devices are in probe/remove() because it assures that the
> device is suspended after the probe.
> It seems that the device might be kept on after probe and before the
> first iommu_attach if it is default-on.

The default state of these MMUs is on reset and needs to be deasserted
to be used, but you're right, it makes more sense to move
pm_runtime_enable/disable calls to probe/remove. I'll wait a bit, do
this change and resubmit.

Thanks for the comment,

Omar
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