[PATCH v4 1/4] OMAP3: hwmod data: add mmu data for iva and isp

[Ramirez Luna, Omar]

Hi Laurent

On Sun, Dec 25, 2011 at 3:08 PM, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
>> > I'm not sure how this clock stuff works, but I'm guessing the device
>> > is supposed to go to sleep at some points in time, and with your patch
>> > "OMAP3/4: iommu: adapt to runtime pm" it won't, as long as the module
>> > is loaded, unless I'm missing something.
>>
>> The device should be able to be put to sleep at anytime when it is NOT
>> being used. AFAIK there is no mechanism for the main processor (the
>> one running the kernel) to know when the other iommus are not being
>> used, given that they are in independent processors/subsystems, at
>> least for the ones in the DSP or M3 processors. Once the user releases
>> its iommu resource it means it is no longer using it, at that point
>> the device can be put to sleep.
>
> How should the OMAP3 ISP driver proceed to make sure that its IOMMU is clocked
> off when it doesn't need it ?

If there is an specific scenario where the iommu should be disabled,
iommu_detach_device can be called to release the iommu resource. On
suspend/resume scenarios runtime pm callbacks should still be able to
put the device in idle.

Regards,

Omar