Re: [RFC/PATCH 3/3] omap3-iommu: remote registration

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On Mon, May 18, 2009 at 4:02 PM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
> On Mon, May 18, 2009 at 03:46:07PM +0300, Felipe Contreras wrote:
>> On Mon, May 18, 2009 at 3:11 PM, Russell King - ARM Linux
>> <linux@xxxxxxxxxxxxxxxx> wrote:
>> > The real problem here seems to be the TI DSP bridge code, and if that's
>> > the case why can't we just avoid registering IVA2 if the TI DSP bridge
>> > code is enabled.  That solves your stated problem without creating
>> > additional management issues.
>>
>> The bridgedriver is expected to move and use iommu eventually, but not
>> right now, so I guess the iva2 device should be registered only if
>> MPU_BRIDGE_IOMMU is defined.
>>
>> But then what's the point of having the isp iommu device if the camera
>> driver is disabled? Wouldn't that be wasting resources? Then if CAMERA
>> is not defined the isp device should not be registered either.
>
> So have something like:
>
> config OMAP_IOMMU
>        tristate
>
> and then have both MPU_BRIDGE_IOMMU and the camera support (and whatever
> else) select it.  That way, you only end up with the IOMMU support code
> built into the kernel if you have users of it.
>
> These low-level internal services drivers really don't need to be
> publically visible in the configuration system.

Yeap, that needs to be done too.

> As for the run-time size, that's truely minimal.

I thought creating iommu devices involved some kind of overhead,
allocating some resources probably. That's why the iva2 iommu device
conflicts with tidspbridge custom mmu.

>> And finally if none of the two are enabled then you don't really
>> iommu. By having omap_iommu_add all the dependencies would be handled
>> automatically, right? 'modprobe bridgedriver' would load iommu.
>
> Think about it - the dependencies _already_ have to be there to use
> the iommu services.

Ok, yes, for iommu, but not for omap3-iommu which is a separate module.

-- 
Felipe Contreras
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