Re: [PATCH 1/9] iommu/of: Drop early initialisation hooks

[Robin Murphy]

Hi Jeffy,

On 11/01/18 11:14, JeffyChen wrote:
> Hi Marek,
>
> Thanks for your reply.
>
> On 01/11/2018 05:40 PM, Marek Szyprowski wrote:
> > Hi Jeffy,
> >
> > On 2018-01-11 09:22, Jeffy Chen wrote:
> > > With the probe-deferral mechanism, early initialisation hooks are no
> > > longer needed.
> > >
> > > Suggested-by: Robin Murphy <robin.murphy@xxxxxxx>

In fact, shortly after I said that I had a "how hard can it be?" moment 
and took a crack at it myself - sorry, I should probably have cc'd you 
on that series[1].

> > > Signed-off-by: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx>
> > > ---
> > >
> > >  drivers/iommu/arm-smmu-v3.c | 2 +-
> > > Â drivers/iommu/arm-smmu.cÂÂÂÂ | 12 ++++++------
> > > Â drivers/iommu/exynos-iommu.c |Â 2 +-
> >
> > For Exynos IOMMU:
> > Acked-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> >
> > IPMMU and MSM IOMMU are no longer multi-platform safe after this patch.
> > It breaks them in the same way as my commit 928055a01b3f ("iommu/exynos:
> > Remove custom platform device registration code") broke Exynos IOMMU.
> >
> > You need a similar fix for them:
> > https://www.spinics.net/lists/arm-kernel/msg627648.html
>
> hmmm, right, i did saw this fix in the rockchip iommu driver too.
>
> and there're also some other iommu drivers put bus_set_iommu in their 
> probe() to avoid that.
>
> maybe we can do it in the iommu framework?
>
> for example:
> 1/ add a bus type member to struct iommu_device
> 2/ and a iommu_device_set_bus()
> 3/ do the bus_set_iommu stuff in iommu_device_register()
> 4/ undo bus_set_iommu in iommu_device_unregister()

Ultimately we'd like to get rid of the bus relationship altogether, so I 
don't think it's really worth adding more infrastructure around it. 
Having of-iommu-based drivers set bus ops at probe time, and others 
conditionally from an initcall, is pretty clean and simple, so I'd 
rather stick with that approach for now.

Robin.

[1] 
https://lists.linuxfoundation.org/pipermail/iommu/2018-January/025395.html