Re: [PATCH v3 00/10] Preemption support for A7XX

[Akhil P Oommen]

On Thu, Sep 05, 2024 at 04:51:18PM +0200, Antonino Maniscalco wrote:
> This series implements preemption for A7XX targets, which allows the GPU to
> switch to an higher priority ring when work is pushed to it, reducing latency
> for high priority submissions.
> 
> This series enables L1 preemption with skip_save_restore which requires
> the following userspace patches to function:
> 
> https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30544
> 
> A flag is added to `msm_submitqueue_create` to only allow submissions
> from compatible userspace to be preempted, therefore maintaining
> compatibility.
> 
> Preemption is currently only enabled by default on A750, it can be
> enabled on other targets through the `enable_preemption` module
> parameter. This is because more testing is required on other targets.
> 
> For testing on other HW it is sufficient to set that parameter to a
> value of 1, then using the branch of mesa linked above, `TU_DEBUG=hiprio`
> allows to run any application as high priority therefore preempting
> submissions from other applications.
> 
> The `msm_gpu_preemption_trigger` and `msm_gpu_preemption_irq` traces
> added in this series can be used to observe preemption's behavior as
> well as measuring preemption latency.
> 
> Some commits from this series are based on a previous series to enable
> preemption on A6XX targets:
> 
> https://lkml.kernel.org/1520489185-21828-1-git-send-email-smasetty@xxxxxxxxxxxxxx
> 
> Signed-off-by: Antonino Maniscalco <antomani103@xxxxxxxxx>

Antonino, can you please test this once with per-process pt disabled to
ensure that is not broken? It is handy sometimes while debugging.
We just need to remove "adreno-smmu" compatible string from gpu smmu
node in DT.

-Akhil.

> ---
> Changes in v3:
> - Added documentation about preemption
> - Use quirks to determine which target supports preemption
> - Add a module parameter to force disabling or enabling preemption
> - Clear postamble when profiling
> - Define A6XX_CP_CONTEXT_SWITCH_CNTL_LEVEL fields in a6xx.xml
> - Make preemption records MAP_PRIV
> - Removed user ctx record (NON_PRIV) and patch 2/9 as it's not needed
>   anymore
> - Link to v2: https://lore.kernel.org/r/20240830-preemption-a750-t-v2-0-86aeead2cd80@xxxxxxxxx
> 
> Changes in v2:
> - Added preept_record_size for X185 in PATCH 3/7
> - Added patches to reset perf counters
> - Dropped unused defines
> - Dropped unused variable (fixes warning)
> - Only enable preemption on a750
> - Reject MSM_SUBMITQUEUE_ALLOW_PREEMPT for unsupported targets
> - Added Akhil's Reviewed-By tags to patches 1/9,2/9,3/9
> - Added Neil's Tested-By tags
> - Added explanation for UAPI changes in commit message
> - Link to v1: https://lore.kernel.org/r/20240815-preemption-a750-t-v1-0-7bda26c34037@xxxxxxxxx
> 
> ---
> Antonino Maniscalco (10):
>       drm/msm: Fix bv_fence being used as bv_rptr
>       drm/msm: Add a `preempt_record_size` field
>       drm/msm: Add CONTEXT_SWITCH_CNTL bitfields
>       drm/msm/A6xx: Implement preemption for A7XX targets
>       drm/msm/A6xx: Sync relevant adreno_pm4.xml changes
>       drm/msm/A6xx: Use posamble to reset counters on preemption
>       drm/msm/A6xx: Add traces for preemption
>       drm/msm/A6XX: Add a flag to allow preemption to submitqueue_create
>       drm/msm/A6xx: Enable preemption for A750
>       Documentation: document adreno preemption
> 
>  Documentation/gpu/msm-preemption.rst               |  98 +++++
>  drivers/gpu/drm/msm/Makefile                       |   1 +
>  drivers/gpu/drm/msm/adreno/a6xx_catalog.c          |   7 +-
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c              | 331 +++++++++++++++-
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.h              | 166 ++++++++
>  drivers/gpu/drm/msm/adreno/a6xx_preempt.c          | 430 +++++++++++++++++++++
>  drivers/gpu/drm/msm/adreno/adreno_gpu.h            |   9 +-
>  drivers/gpu/drm/msm/msm_drv.c                      |   4 +
>  drivers/gpu/drm/msm/msm_gpu_trace.h                |  28 ++
>  drivers/gpu/drm/msm/msm_ringbuffer.h               |   8 +
>  drivers/gpu/drm/msm/msm_submitqueue.c              |   3 +
>  drivers/gpu/drm/msm/registers/adreno/a6xx.xml      |   7 +-
>  .../gpu/drm/msm/registers/adreno/adreno_pm4.xml    |  39 +-
>  include/uapi/drm/msm_drm.h                         |   5 +-
>  14 files changed, 1094 insertions(+), 42 deletions(-)
> ---
> base-commit: 7c626ce4bae1ac14f60076d00eafe71af30450ba
> change-id: 20240815-preemption-a750-t-fcee9a844b39
> 
> Best regards,
> -- 
> Antonino Maniscalco <antomani103@xxxxxxxxx>
>