Re: [RFC PATCH 00/18] drm/panthor: Add Mali v15 AM virtualization support

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 28 May 2026 16:05:28 +0100
Karunika Choo <karunika.choo@arm.com> wrote:

> This series adds initial support for Mali v15 AM GPUs and the
> HW-assisted virtualization blocks around them.
> 
> The first patches make the core panthor code less dependent on fixed
> register layouts by caching decoded GPU_ID fields and moving register
> base offsets into the HW description. Mali v15 support is then added on
> top, including 64-bit GPU_ID decoding and optional devfreq handling for
> systems where frequency control is owned by AM_GOVERNOR.
> 
> The rest of the series introduces the AM_SYSTEM, AM_PARTITION_CONTROL,
> AM_RESOURCE_GROUP, arbitration scheduler and access-window pieces needed
> to coordinate GPU ownership between the arbiter and VM-side panthor
> instances. Finally, HW component PM is routed through access windows and
> waits are taught to tolerate loss of the access window.
> 
> This series has a soft dependency on firmware scheduling support that
> will be added later to handle YIELD_NOW interrupts.
> 
> The resulting support is intentionally minimal, but provides the
> driver-side plumbing needed for Mali v15 AM systems.
> 
> Kind regards,
> Karunika Choo
> 
> Karunika Choo (18):
>   drm/panthor: Ignore -EOPNOTSUPP for shader-present nvmem lookup
>   drm/panthor: Move register access helpers out of panthor_device.h
>   drm/panthor: Parse and store GPU_ID fields
>   drm/panthor: Add 64-bit GPU_ID decoding for v15 GPUs
>   drm/panthor: Move register base offsets to the HW description
>   drm/panthor: Derive MMU AS register addresses from base and stride
>   drm/panthor: Add Mali v15 hardware support
>   drm/panthor: Skip devfreq when no OPP table is present

The prep patches look mostly okay to me (baring a few nitpicks).

>   drm/panthor: Add basic AM_SYSTEM support
>   drm/panthor: Add AM_PARTITION_CONTROL support
>   drm/panthor: Add AM message helpers
>   drm/panthor: Add AM_RESOURCE_GROUP support
>   drm/panthor: Add arbitration scheduler
>   drm/panthor: Route arbitration events
>   drm/panthor: Add access-window support
>   drm/panthor: Synchronize HW component PM transitions
>   drm/panthor: Route HW component PM through access windows
>   drm/panthor: Tolerate access-window loss during HW waits

For those, I think I'd like to have the full picture before providing a
proper review. Right now it's unclear what the FW-based YIELD looks
like, and the retry-mechanism on an access-window-lost seems a bit
fragile (the only places where I've seen this tested is in iopoll
loops, but AW can go away at any time).

> 
>  drivers/gpu/drm/panthor/Kconfig               |  14 +
>  drivers/gpu/drm/panthor/Makefile              |   3 +
>  drivers/gpu/drm/panthor/arbitration/Makefile  |  17 +
>  .../panthor/arbitration/panthor_arbitration.h |  45 ++
>  .../arbitration/panthor_arbitration_drv.c     | 199 +++++
>  .../arbitration/panthor_arbitration_sched.c   | 692 ++++++++++++++++++
>  .../arbitration/panthor_arbitration_sched.h   |  25 +
>  .../arbitration/panthor_partition_control.c   | 390 ++++++++++
>  .../arbitration/panthor_partition_control.h   |  27 +
>  .../arbitration/panthor_resource_group.c      | 288 ++++++++
>  .../arbitration/panthor_resource_group.h      |  20 +
>  drivers/gpu/drm/panthor/panthor_am_msg.h      | 157 ++++
>  drivers/gpu/drm/panthor/panthor_aw.c          | 576 +++++++++++++++
>  drivers/gpu/drm/panthor/panthor_aw.h          |  46 ++
>  drivers/gpu/drm/panthor/panthor_devfreq.c     |  13 +-
>  drivers/gpu/drm/panthor/panthor_device.c      |  69 +-
>  drivers/gpu/drm/panthor/panthor_device.h      | 134 ++--
>  drivers/gpu/drm/panthor/panthor_device_io.h   |  81 ++
>  drivers/gpu/drm/panthor/panthor_drv.c         |   1 +
>  drivers/gpu/drm/panthor/panthor_fw.c          |   8 +-
>  drivers/gpu/drm/panthor/panthor_fw_regs.h     |   2 -
>  drivers/gpu/drm/panthor/panthor_gpu.c         |  14 +-
>  .../drm/panthor/panthor_gpu_discover_regs.h   |  42 ++
>  drivers/gpu/drm/panthor/panthor_gpu_regs.h    |   2 -
>  drivers/gpu/drm/panthor/panthor_heap.c        |   3 +-
>  drivers/gpu/drm/panthor/panthor_hw.c          | 163 ++++-
>  drivers/gpu/drm/panthor/panthor_hw.h          |  45 +-
>  drivers/gpu/drm/panthor/panthor_mmu.c         |  36 +-
>  drivers/gpu/drm/panthor/panthor_mmu_regs.h    |  23 +-
>  drivers/gpu/drm/panthor/panthor_pwr.c         |  32 +-
>  drivers/gpu/drm/panthor/panthor_pwr_regs.h    |   3 -
>  drivers/gpu/drm/panthor/panthor_sched.c       |   9 +-
>  drivers/gpu/drm/panthor/system/Makefile       |  12 +
>  .../gpu/drm/panthor/system/panthor_system.c   | 298 ++++++++
>  include/uapi/drm/panthor_drm.h                |  20 +-
>  35 files changed, 3338 insertions(+), 171 deletions(-)
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/Makefile
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_arbitration.h
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_arbitration_drv.c
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_arbitration_sched.c
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_arbitration_sched.h
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_partition_control.c
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_partition_control.h
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_resource_group.c
>  create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_resource_group.h
>  create mode 100644 drivers/gpu/drm/panthor/panthor_am_msg.h
>  create mode 100644 drivers/gpu/drm/panthor/panthor_aw.c
>  create mode 100644 drivers/gpu/drm/panthor/panthor_aw.h
>  create mode 100644 drivers/gpu/drm/panthor/panthor_device_io.h
>  create mode 100644 drivers/gpu/drm/panthor/panthor_gpu_discover_regs.h
>  create mode 100644 drivers/gpu/drm/panthor/system/Makefile
>  create mode 100644 drivers/gpu/drm/panthor/system/panthor_system.c
> 
> --
> 2.43.0
>