linux/Documentation/gpu/panfrost.rst
Adrián Larumbe b12f3ea7c1 drm/panfrost: Replace fdinfo's profiling debugfs knob with sysfs
Debugfs isn't always available in production builds that try to squeeze
every single byte out of the kernel image, but we still need a way to
toggle the timestamp and cycle counter registers so that jobs can be
profiled for fdinfo's drm engine and cycle calculations.

Drop the debugfs knob and replace it with a sysfs file that accomplishes
the same functionality, and document its ABI in a separate file.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240306015819.822128-2-adrian.larumbe@collabora.com
2024-03-11 13:27:10 +01:00

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.. SPDX-License-Identifier: GPL-2.0+
=========================
drm/Panfrost Mali Driver
=========================
.. _panfrost-usage-stats:
Panfrost DRM client usage stats implementation
==============================================
The drm/Panfrost driver implements the DRM client usage stats specification as
documented in :ref:`drm-client-usage-stats`.
Example of the output showing the implemented key value pairs and entirety of
the currently possible format options:
::
pos: 0
flags: 02400002
mnt_id: 27
ino: 531
drm-driver: panfrost
drm-client-id: 14
drm-engine-fragment: 1846584880 ns
drm-cycles-fragment: 1424359409
drm-maxfreq-fragment: 799999987 Hz
drm-curfreq-fragment: 799999987 Hz
drm-engine-vertex-tiler: 71932239 ns
drm-cycles-vertex-tiler: 52617357
drm-maxfreq-vertex-tiler: 799999987 Hz
drm-curfreq-vertex-tiler: 799999987 Hz
drm-total-memory: 290 MiB
drm-shared-memory: 0 MiB
drm-active-memory: 226 MiB
drm-resident-memory: 36496 KiB
drm-purgeable-memory: 128 KiB
Possible `drm-engine-` key names are: `fragment`, and `vertex-tiler`.
`drm-curfreq-` values convey the current operating frequency for that engine.
Users must bear in mind that engine and cycle sampling are disabled by default,
because of power saving concerns. `fdinfo` users and benchmark applications which
query the fdinfo file must make sure to toggle the job profiling status of the
driver by writing into the appropriate sysfs node::
echo <N> > /sys/bus/platform/drivers/panfrost/[a-f0-9]*.gpu/profiling
Where `N` is either `0` or `1`, depending on the desired enablement status.