Re: [PATCH 00/13] drm/msm: Add PERFCNTR_CONFIG ioctl

[Dmitry Baryshkov]

On Mon, Apr 20, 2026 at 03:25:22PM -0700, Rob Clark wrote:
> Add a new PERFCNTR_CONFIG ioctl, serving two functions:
> 
> 1. Global counter collection (restricted to perfmon_capable()) using the
>    MSM_PERFCNTR_STREAM flag.  Global counter sampling is, global, across
>    contexts.  Only a single global counter stream is allowed at a time.
> 2. Reserve counters for local counter collection.  Local counter
>    collection is local to a cmdstream (GEM_SUBMIT), and as such is
>    allowed in all processes without additional privileges.
> 
> The kernel enforces that counters assigned for global counter collection
> do not conflict with counters reserved for local counter collection, and
> visa versa.  Since local counter collection is scoped to a single cmd-
> stream, multiple UMD processes can overlap in their reserved counters.
> But cannot conflict with global counter usage.
> 
> In the case of local counter collection, the UMD is still responsible
> for programming the corresponding SELect registers, and sampling the
> counter values, from it's cmdstream.  But by performing the reservation
> step, the UMD protects itself from the kernel trying to use the same
> SEL/counter regs for global counter collection.
> 
> For global counter collection, the kernel programs SEL regs, and sets up
> a timer for counter sampling.  Userspace reads out the sampled values
> from the returned perfcntr stream fd.  Releasing the global perfcntr
> stream is simply a matter of close()ing the fd.
> 
> Since the counter sampling is done in the kernel, this prepares us for
> not having to disable IFPC while global counter sampling is active.  But
> wiring this up will come in a later patch.
> 
> The mesa side of this is at:
> https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40522
> 
> Rob Clark (13):
>   drm/msm: Remove obsolete perf infrastructure
>   drm/msm/adreno: Sync registers from mesa
>   drm/msm/registers: Sync gen_header.py from mesa
>   drm/msm/registers: Add perfcntr json
>   drm/msm: Allow CAP_PERFMON for setting SYSPROF
>   drm/msm: Add a6xx+ perfcntr tables
>   drm/msm: Add sysprof accessors
>   drm/msm/a6xx: Add yield & flush helper
>   drm/msm: Add per-context perfcntr state
>   drm/msm: Add basic perfcntr infrastructure
>   drm/msm/a6xx+: Add support to configure perfcntrs
>   drm/msm/a8xx: Add perfcntr flush sequence
>   drm/msm: Add PERFCNTR_CONFIG ioctl
> 
The series doesn't apply to linux-next. Please switch to b4 and use b4
--edit-deps to specify dependencies.

-- 
With best wishes
Dmitry