Re: [PATCH 7/7] iommu/arm-smmu: Allow building as a module

[Robin Murphy]

On 30/10/2019 15:22, Rob Herring wrote:
> On Wed, Oct 30, 2019 at 02:51:12PM +0000, Will Deacon wrote:
> > By conditionally dropping support for the legacy binding and exporting
> > the newly introduced 'arm_smmu_impl_init()' function we can allow the
> > ARM SMMU driver to be built as a module.
> >
> > Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> > ---
> >   drivers/iommu/Kconfig         | 14 ++++++++-
> >   drivers/iommu/arm-smmu-impl.c |  6 ++++
> >   drivers/iommu/arm-smmu.c      | 54 +++++++++++++++++++++--------------
> >   3 files changed, 51 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > index 7583d47fc4d5..02703f51e533 100644
> > --- a/drivers/iommu/Kconfig
> > +++ b/drivers/iommu/Kconfig
> > @@ -350,7 +350,7 @@ config SPAPR_TCE_IOMMU
> >   
> >   # ARM IOMMU support
> >   config ARM_SMMU
> > -	bool "ARM Ltd. System MMU (SMMU) Support"
> > +	tristate "ARM Ltd. System MMU (SMMU) Support"
> >   	depends on (ARM64 || ARM) && MMU
> >   	select IOMMU_API
> >   	select IOMMU_IO_PGTABLE_LPAE
> > @@ -362,6 +362,18 @@ config ARM_SMMU
> >   	  Say Y here if your SoC includes an IOMMU device implementing
> >   	  the ARM SMMU architecture.
> >   
> > +config ARM_SMMU_LEGACY_DT_BINDINGS
> > +	bool "Support the legacy \"mmu-masters\" devicetree bindings"
>
> Can't we just remove this now? The only user is Seattle. Is anyone still
> using Seattle AND DT? There's been no real dts change since Feb '16.
> There's a bit of clean-up needed in the Seattle dts files, so I'd like
> to remove them if there's not users.
>
> If there are users, can't we just make them move to the new binding?
> Yes compatibility, but that really depends on the users caring.

Apparently it's also in the wild on Cavium ThunderX/OcteonTX machines as 
well :(

> I though Calxeda was using this too, but I guess we didn't get that
> finished. We should probably remove that secure mode flag as well.

FWIW the secure quirk still comes in useful every now and then when 
people prototype stuff on 32-bit VExpress, where it turns out an SMMU is 
about the only thing which cares whether you're running Linux in Secure 
mode or not.

Robin.