Re: [RFC PATCH 2/2] arm64: mm: add SMCCC-backed cache invalidate provider

[Conor Dooley <conor@kernel.org>]

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On Thu, May 21, 2026 at 12:18:12PM +0100, Jonathan Cameron wrote:
> On Thu, 21 May 2026 07:30:47 +0000
> Srirangan Madhavan <smadhavan@nvidia.com> wrote:
> 
> > Add an arm64 cache maintenance backend that discovers SMCCC cache
> > clean+invalidate support, queries attributes, handles transient BUSY and
> > RATE_LIMITED responses with bounded retries, and registers with the generic
> > cache coherency framework.
> > 
> > Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
> Hi Srirangan,
> 
> Other than the file location and Kconfig option comments, everything else
> is really trivial. + some musings about maybe being worth more clever
> fusing of ops in the future if it turns out to be useful.
> 
> > ---
> >  MAINTAINERS                 |   1 +
> >  arch/arm64/mm/Makefile      |   1 +
> >  arch/arm64/mm/cache_maint.c | 180 ++++++++++++++++++++++++++++++++++++
> 
> File location wise, this is a driver for a subsystem, be it one closely
> coupled to arm.  Arm maintainers, do you want it in there or in drivers/cache ?
> My personal preference is always to keep drivers with subsystems but I don't
> care that much.

At the risk of stepping on Will's/Catalin's toes, I'll butt in here..

If this was on riscv, using an ecall into sbi firmware, I'd be asking
for it to be put in drivers/cache. The mechanism for requesting the
ops is arch-specific, but the actual execution of it is not, right?
The actual execution is going to depend on the device-specific
firmware that the smc is made to. That puts it in the same boat as
clk-scmi to me, but I'm not really familiar with how these things break
down on arm64 to be sure.

> >  3 files changed, 182 insertions(+)
> >  create mode 100644 arch/arm64/mm/cache_maint.c
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 2fb1c75afd16..33c35f8e6e40 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -25383,6 +25383,7 @@ M:	Jonathan Cameron <jic23@kernel.org>
> >  S:	Maintained
> >  T:	git https://git.kernel.org/pub/scm/linux/kernel/git/conor/linux.git/
> >  F:	Documentation/devicetree/bindings/cache/
> > +F:	arch/arm64/mm/cache_maint.c
> 
> I wonder if this should just have a separate maintainers entry? 
> We did that for the hisi driver.
> 
> If not maybe add yourself as at least a Reviewer so that you get +CC'd
> on relevant changes.
> 
> Conor, what do you think makes sense here.

I think it is very weird to have an arch/arm64/mm file in this entry,
implying that I would be applying patches for it, which I do not
consider to be appropriate. If it gets moved to drivers/cache, then it
I think a standalone maintainers entry for the driver is a good idea.

Cheers,
Conor.

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