[PATCH v8 5/5] drm/panthor: add sysfs knob for enabling job profiling

Adrián Larumbe
2024-09-23T23:09:55Z

This commit introduces a DRM device sysfs attribute that lets UM control
the job accounting status in the device. The knob variable had been brought
in as part of a previous commit, but now we're able to fix it manually.

As sysfs files are part of a driver's uAPI, describe its legitimate input
values and output format in a documentation file.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
---
.../testing/sysfs-driver-panthor-profiling | 10 ++++
Documentation/gpu/panthor.rst | 46 +++++++++++++++++++
drivers/gpu/drm/panthor/panthor_drv.c | 39 ++++++++++++++++
3 files changed, 95 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-driver-panthor-profiling
create mode 100644 Documentation/gpu/panthor.rst

diff --git a/Documentation/ABI/testing/sysfs-driver-panthor-profiling b/Documentation/ABI/testing/sysfs-driver-panthor-profiling
new file mode 100644
index 000000000000..af05fccedc15
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-panthor-profiling
@@ -0,0 +1,10 @@
+What: /sys/bus/platform/drivers/panthor/.../profiling
+Date: September 2024
+KernelVersion: 6.11.0
+Contact: Adrian Larumbe <adrian.larumbe@collabora.com>
+Description:
+ Bitmask to enable drm fdinfo's job profiling measurements.
+ Valid values are:
+ 0: Don't enable fdinfo job profiling sources.
+ 1: Enable GPU cycle measurements for running jobs.
+ 2: Enable GPU timestamp sampling for running jobs.
diff --git a/Documentation/gpu/panthor.rst b/Documentation/gpu/panthor.rst
new file mode 100644
index 000000000000..cbf5c4429a2d
--- /dev/null
+++ b/Documentation/gpu/panthor.rst
@@ -0,0 +1,46 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+=========================
+ drm/Panthor CSF driver
+=========================
+
+.. _panfrost-usage-stats:
+
+Panthor DRM client usage stats implementation
+==============================================
+
+The drm/Panthor 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: 29
+ ino: 491
+ drm-driver: panthor
+ drm-client-id: 10
+ drm-engine-panthor: 111110952750 ns
+ drm-cycles-panthor: 94439687187
+ drm-maxfreq-panthor: 1000000000 Hz
+ drm-curfreq-panthor: 1000000000 Hz
+ drm-total-memory: 16480 KiB
+ drm-shared-memory: 0
+ drm-active-memory: 16200 KiB
+ drm-resident-memory: 16480 KiB
+ drm-purgeable-memory: 0
+
+Possible `drm-engine-` key names are: `panthor`.
+`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/panthor/[a-f0-9]*.gpu/profiling
+
+Where `N` is a bit mask where cycle and timestamp sampling are respectively
+enabled by the first and second bits.
diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index 233b265c0819..6f47d9d1d86a 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -1513,6 +1513,44 @@ static void panthor_remove(struct platform_device *pdev)
panthor_device_unplug(ptdev);
}

+static ssize_t profiling_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct panthor_device *ptdev = dev_get_drvdata(dev);
+
+ return sysfs_emit(buf, "%d\n", ptdev->profile_mask);
+}
+
+static ssize_t profiling_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct panthor_device *ptdev = dev_get_drvdata(dev);
+ u32 value;
+ int err;
+
+ err = kstrtou32(buf, 0, &value);
+ if (err)
+ return err;
+
+ if ((value & ~PANTHOR_DEVICE_PROFILING_ALL) != 0)
+ return -EINVAL;
+
+ ptdev->profile_mask = value;
+
+ return len;
+}
+
+static DEVICE_ATTR_RW(profiling);
+
+static struct attribute *panthor_attrs[] = {
+ &dev_attr_profiling.attr,
+ NULL,
+};
+
+ATTRIBUTE_GROUPS(panthor);
+
static const struct of_device_id dt_match[] = {
{ .compatible = "rockchip,rk3588-mali" },
{ .compatible = "arm,mali-valhall-csf" },
@@ -1532,6 +1570,7 @@ static struct platform_driver panthor_driver = {
.name = "panthor",
.pm = pm_ptr(&panthor_pm_ops),
.of_match_table = dt_match,
+ .dev_groups = panthor_groups,
},
};

--
2.46.0