Re: [PATCH 3/6] sparc64: Initialize iommu_map_table and iommu_pool

[tndave]

On 10/24/2016 10:47 AM, David Miller wrote:
> From: Tushar Dave <tushar.n.dave@xxxxxxxxxx>
> Date: Mon, 10 Oct 2016 11:12:04 -0700
>
> > Like legacy IOMMU, use common iommu_map_table and iommu_pool for ATU.
> > This change initializes iommu_map_table and iommu_pool for ATU.
> >
> > Signed-off-by: Tushar Dave <tushar.n.dave@xxxxxxxxxx>
> > Reviewed-by: chris hyser <chris.hyser@xxxxxxxxxx>
> > Reviewed-by: Sowmini Varadhan <sowmini.varadhan@xxxxxxxxxx>
>
> I suspect you are adding a bisection problem here.
>
> It looks to me like patch #2 starts setting up to use the ATU
> but these changes in #3 and later are necessary for it to even
> work properly.
>
> You can't leave the tree in an intermediate non-working state
> between changes like that.
I agree but even if you apply only patch #1, #2 things still work using
legacy IOMMU. (and the same is true for rest of the other patches i.e.
#3, #4, #5).

All the patches, except patch #6 , sets up needed data structures and
functions for ATU however ATU will only be used in action after you
apply patch #6 which actually enables 64bit DMA. Until then, things are
going to work using legacy IOMMU with 32bit DMA.

Thanks.

-Tushar
>