linux-kernel - Re: [PATCH v5 4/4] drm/panthor: add sysfs knob for enabling job profiling

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Message-ID: <20240904100743.225f1837@collabora.com>
Date: Wed, 4 Sep 2024 10:07:43 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Sumit Semwal
 <sumit.semwal@...aro.org>, Christian König
 <christian.koenig@....com>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v5 4/4] drm/panthor: add sysfs knob for enabling job
 profiling

On Tue,  3 Sep 2024 21:25:38 +0100
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> 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@...labora.com>
> ---
>  Documentation/gpu/panthor.rst         | 46 +++++++++++++++++++++++++++
>  drivers/gpu/drm/panthor/panthor_drv.c | 39 +++++++++++++++++++++++
>  2 files changed, 85 insertions(+)
>  create mode 100644 Documentation/gpu/panthor.rst
> 
> 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.

This should probably be documented in
Documentation/ABI/testing/sysfs-driver-panthor too.

> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> index e18838754963..26475db96c41 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -1450,6 +1450,44 @@ 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" },
> @@ -1469,6 +1507,7 @@ static struct platform_driver panthor_driver = {
>  		.name = "panthor",
>  		.pm = pm_ptr(&panthor_pm_ops),
>  		.of_match_table = dt_match,
> +		.dev_groups = panthor_groups,
>  	},
>  };
>