Re: [PATCH v2 1/4] iommu/arm-smmu: Introduce wrapper for writeq/readq

[Robin Murphy]

On 20/08/2019 13:08, Will Deacon wrote:
> Hi Gregory, Hanna,
>
> On Thu, Jul 11, 2019 at 05:02:39PM +0200, Gregory CLEMENT wrote:
> > From: Hanna Hawa <hannah@xxxxxxxxxxx>
> >
> > This patch introduces the smmu_writeq_relaxed/smmu_readq_relaxed
> > helpers, as preparation to add specific Marvell work-around for
> > accessing 64 bits width registers of ARM SMMU.
> >
> > Signed-off-by: Hanna Hawa <hannah@xxxxxxxxxxx>
> > Signed-off-by: Gregory CLEMENT <gregory.clement@xxxxxxxxxxx>
> > ---
> >   drivers/iommu/arm-smmu.c | 36 +++++++++++++++++++++++++++---------
> >   1 file changed, 27 insertions(+), 9 deletions(-)
>
> Sorry for the delay in replying to this -- Robin's been reworking the driver
> so that implementation quirks can be specified more cleanly. Please can you
> take a look at:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=for-joerg/arm-smmu/refactoring
>
> and try to respin your patches on top of that?

Right, the arm_smmu_impl design was specifically anticipating this quirk 
as well - it should just be a case of a cfg_probe hook to hide the 
features which can't work, plus {read,write}_reg64 hooks to override any 
remaining 64-bit accesses with the explicit hi_lo_* variants, munged 
together (either statically or dynamically) with the standard MMU-500 hooks.

Robin.