Some socs such as mt8196 require custom ASN hash.

Chia-I Wu (2):
  dt-bindings: gpu: mali-valhall-csf: add asn-hash
  drm/panthor: add asn-hash support

 .../bindings/gpu/arm,mali-valhall-csf.yaml    |  8 ++++++
 drivers/gpu/drm/panthor/panthor_device.c      | 28 +++++++++++++++++++
 drivers/gpu/drm/panthor/panthor_device.h      |  6 ++++
 drivers/gpu/drm/panthor/panthor_gpu.c         | 17 +++++++++++
 drivers/gpu/drm/panthor/panthor_regs.h        |  4 +++
 5 files changed, 63 insertions(+)

-- 
2.51.0.318.gd7df087d1a-goog

On 28/08/2025 21:18, Chia-I Wu wrote:
> Some socs such as mt8196 require custom ASN hash.

I don't know the full details of this, but I'm puzzled by the "require"
here.

AIUI the "custom ASN hash support" (or L2C_SLICE_HASH as it was renamed)
affects the efficiency of the L2 caches in the GPU. It basically
determines how addresses are striped over the individual caches.

So (unless there is a specific errata) not setting a custom hash will
work just fine, but the performance might be slightly reduced.

kbase provides both a DT option and a module parameter which can be used
to override the defaults (although the parameter descriptions say "for
testing" which I think is somewhat telling).

How we should describe this somewhat depends on whether this is a
specific workaround for a SoC - in which case Boris's suggestion of
using a different compatible string and panthor_soc_data seems like a
good choice. Or if this is exposed as a general "tuning" parameter, in
which case this might be appropriate.

I believe the tuning is related to more than just a SoC (the external
memory system has an impact). So I guess a DT level knob makes most
sense here.

Steve

> Chia-I Wu (2):
>   dt-bindings: gpu: mali-valhall-csf: add asn-hash
>   drm/panthor: add asn-hash support
> 
>  .../bindings/gpu/arm,mali-valhall-csf.yaml    |  8 ++++++
>  drivers/gpu/drm/panthor/panthor_device.c      | 28 +++++++++++++++++++
>  drivers/gpu/drm/panthor/panthor_device.h      |  6 ++++
>  drivers/gpu/drm/panthor/panthor_gpu.c         | 17 +++++++++++
>  drivers/gpu/drm/panthor/panthor_regs.h        |  4 +++
>  5 files changed, 63 insertions(+)
>

On Fri, Aug 29, 2025 at 6:41 AM Steven Price <steven.price@arm.com> wrote:
>
> On 28/08/2025 21:18, Chia-I Wu wrote:
> > Some socs such as mt8196 require custom ASN hash.
>
> I don't know the full details of this, but I'm puzzled by the "require"
> here.
>
> AIUI the "custom ASN hash support" (or L2C_SLICE_HASH as it was renamed)
> affects the efficiency of the L2 caches in the GPU. It basically
> determines how addresses are striped over the individual caches.
>
> So (unless there is a specific errata) not setting a custom hash will
> work just fine, but the performance might be slightly reduced.
All memory access results in faults unless custom ASN hash is enabled on mt8196.

It sounds like this is a soc-specific quirk.  I will check with the
vendor, and likely turn this into a quirk.

>
> kbase provides both a DT option and a module parameter which can be used
> to override the defaults (although the parameter descriptions say "for
> testing" which I think is somewhat telling).
>
> How we should describe this somewhat depends on whether this is a
> specific workaround for a SoC - in which case Boris's suggestion of
> using a different compatible string and panthor_soc_data seems like a
> good choice. Or if this is exposed as a general "tuning" parameter, in
> which case this might be appropriate.
>
> I believe the tuning is related to more than just a SoC (the external
> memory system has an impact). So I guess a DT level knob makes most
> sense here.
>
> Steve
>
> > Chia-I Wu (2):
> >   dt-bindings: gpu: mali-valhall-csf: add asn-hash
> >   drm/panthor: add asn-hash support
> >
> >  .../bindings/gpu/arm,mali-valhall-csf.yaml    |  8 ++++++
> >  drivers/gpu/drm/panthor/panthor_device.c      | 28 +++++++++++++++++++
> >  drivers/gpu/drm/panthor/panthor_device.h      |  6 ++++
> >  drivers/gpu/drm/panthor/panthor_gpu.c         | 17 +++++++++++
> >  drivers/gpu/drm/panthor/panthor_regs.h        |  4 +++
> >  5 files changed, 63 insertions(+)
> >
>