Re: [PATCH v3 1/1] drm/panfrost: Replace fdinfo's profiling debugfs knob with sysfs

[Steven Price]

On 06/03/2024 01:56, Adrián Larumbe wrote:
> 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@xxxxxxxxxxxxx>

Reviewed-by: Steven Price <steven.price@xxxxxxx>

> ---
>  .../testing/sysfs-driver-panfrost-profiling   | 10 +++++
>  Documentation/gpu/panfrost.rst                |  9 ++++
>  drivers/gpu/drm/panfrost/Makefile             |  2 -
>  drivers/gpu/drm/panfrost/panfrost_debugfs.c   | 21 ----------
>  drivers/gpu/drm/panfrost/panfrost_debugfs.h   | 14 -------
>  drivers/gpu/drm/panfrost/panfrost_device.h    |  2 +-
>  drivers/gpu/drm/panfrost/panfrost_drv.c       | 41 ++++++++++++++++---
>  drivers/gpu/drm/panfrost/panfrost_job.c       |  2 +-
>  8 files changed, 57 insertions(+), 44 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-driver-panfrost-profiling
>  delete mode 100644 drivers/gpu/drm/panfrost/panfrost_debugfs.c
>  delete mode 100644 drivers/gpu/drm/panfrost/panfrost_debugfs.h
> 
> diff --git a/Documentation/ABI/testing/sysfs-driver-panfrost-profiling b/Documentation/ABI/testing/sysfs-driver-panfrost-profiling
> new file mode 100644
> index 000000000000..1d8bb0978920
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-panfrost-profiling
> @@ -0,0 +1,10 @@
> +What:		/sys/bus/platform/drivers/panfrost/.../profiling
> +Date:		February 2024
> +KernelVersion:	6.8.0
> +Contact:	Adrian Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
> +Description:
> +		Get/set drm fdinfo's engine and cycles profiling status.
> +		Valid values are:
> +		0: Don't enable fdinfo job profiling sources.
> +		1: Enable fdinfo job profiling sources, this enables both the GPU's
> +		   timestamp and cycle counter registers.
> \ No newline at end of file
> diff --git a/Documentation/gpu/panfrost.rst b/Documentation/gpu/panfrost.rst
> index b80e41f4b2c5..51ba375fd80d 100644
> --- a/Documentation/gpu/panfrost.rst
> +++ b/Documentation/gpu/panfrost.rst
> @@ -38,3 +38,12 @@ the currently possible format options:
>  
>  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.
> diff --git a/drivers/gpu/drm/panfrost/Makefile b/drivers/gpu/drm/panfrost/Makefile
> index 2c01c1e7523e..7da2b3f02ed9 100644
> --- a/drivers/gpu/drm/panfrost/Makefile
> +++ b/drivers/gpu/drm/panfrost/Makefile
> @@ -12,6 +12,4 @@ panfrost-y := \
>  	panfrost_perfcnt.o \
>  	panfrost_dump.o
>  
> -panfrost-$(CONFIG_DEBUG_FS) += panfrost_debugfs.o
> -
>  obj-$(CONFIG_DRM_PANFROST) += panfrost.o
> diff --git a/drivers/gpu/drm/panfrost/panfrost_debugfs.c b/drivers/gpu/drm/panfrost/panfrost_debugfs.c
> deleted file mode 100644
> index 72d4286a6bf7..000000000000
> --- a/drivers/gpu/drm/panfrost/panfrost_debugfs.c
> +++ /dev/null
> @@ -1,21 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -/* Copyright 2023 Collabora ltd. */
> -/* Copyright 2023 Amazon.com, Inc. or its affiliates. */
> -
> -#include <linux/debugfs.h>
> -#include <linux/platform_device.h>
> -#include <drm/drm_debugfs.h>
> -#include <drm/drm_file.h>
> -#include <drm/panfrost_drm.h>
> -
> -#include "panfrost_device.h"
> -#include "panfrost_gpu.h"
> -#include "panfrost_debugfs.h"
> -
> -void panfrost_debugfs_init(struct drm_minor *minor)
> -{
> -	struct drm_device *dev = minor->dev;
> -	struct panfrost_device *pfdev = platform_get_drvdata(to_platform_device(dev->dev));
> -
> -	debugfs_create_atomic_t("profile", 0600, minor->debugfs_root, &pfdev->profile_mode);
> -}
> diff --git a/drivers/gpu/drm/panfrost/panfrost_debugfs.h b/drivers/gpu/drm/panfrost/panfrost_debugfs.h
> deleted file mode 100644
> index c5af5f35877f..000000000000
> --- a/drivers/gpu/drm/panfrost/panfrost_debugfs.h
> +++ /dev/null
> @@ -1,14 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -/*
> - * Copyright 2023 Collabora ltd.
> - * Copyright 2023 Amazon.com, Inc. or its affiliates.
> - */
> -
> -#ifndef PANFROST_DEBUGFS_H
> -#define PANFROST_DEBUGFS_H
> -
> -#ifdef CONFIG_DEBUG_FS
> -void panfrost_debugfs_init(struct drm_minor *minor);
> -#endif
> -
> -#endif  /* PANFROST_DEBUGFS_H */
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index 62f7e3527385..cffcb0ac7c11 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -130,7 +130,7 @@ struct panfrost_device {
>  	struct list_head scheduled_jobs;
>  
>  	struct panfrost_perfcnt *perfcnt;
> -	atomic_t profile_mode;
> +	bool profile_mode;
>  
>  	struct mutex sched_lock;
>  
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index a926d71e8131..9696702800a4 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -20,7 +20,6 @@
>  #include "panfrost_job.h"
>  #include "panfrost_gpu.h"
>  #include "panfrost_perfcnt.h"
> -#include "panfrost_debugfs.h"
>  
>  static bool unstable_ioctls;
>  module_param_unsafe(unstable_ioctls, bool, 0600);
> @@ -600,10 +599,6 @@ static const struct drm_driver panfrost_drm_driver = {
>  
>  	.gem_create_object	= panfrost_gem_create_object,
>  	.gem_prime_import_sg_table = panfrost_gem_prime_import_sg_table,
> -
> -#ifdef CONFIG_DEBUG_FS
> -	.debugfs_init		= panfrost_debugfs_init,
> -#endif
>  };
>  
>  static int panfrost_probe(struct platform_device *pdev)
> @@ -692,6 +687,41 @@ static void panfrost_remove(struct platform_device *pdev)
>  	drm_dev_put(ddev);
>  }
>  
> +static ssize_t profiling_show(struct device *dev,
> +			      struct device_attribute *attr, char *buf)
> +{
> +	struct panfrost_device *pfdev = dev_get_drvdata(dev);
> +
> +	return sysfs_emit(buf, "%d\n", pfdev->profile_mode);
> +}
> +
> +
> +static ssize_t profiling_store(struct device *dev,
> +			       struct device_attribute *attr,
> +			       const char *buf, size_t len)
> +{
> +	struct panfrost_device *pfdev = dev_get_drvdata(dev);
> +	bool value;
> +	int err;
> +
> +	err = kstrtobool(buf, &value);
> +	if (err)
> +		return err;
> +
> +	pfdev->profile_mode = value;
> +
> +	return len;
> +}
> +
> +static DEVICE_ATTR_RW(profiling);
> +
> +static struct attribute *panfrost_attrs[] = {
> +	&dev_attr_profiling.attr,
> +	NULL,
> +};
> +
> +ATTRIBUTE_GROUPS(panfrost);
> +
>  /*
>   * The OPP core wants the supply names to be NULL terminated, but we need the
>   * correct num_supplies value for regulator core. Hence, we NULL terminate here
> @@ -789,6 +819,7 @@ static struct platform_driver panfrost_driver = {
>  		.name	= "panfrost",
>  		.pm	= pm_ptr(&panfrost_pm_ops),
>  		.of_match_table = dt_match,
> +		.dev_groups = panfrost_groups,
>  	},
>  };
>  module_platform_driver(panfrost_driver);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index 0c2dbf6ef2a5..a61ef0af9a4e 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -243,7 +243,7 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js)
>  	subslot = panfrost_enqueue_job(pfdev, js, job);
>  	/* Don't queue the job if a reset is in progress */
>  	if (!atomic_read(&pfdev->reset.pending)) {
> -		if (atomic_read(&pfdev->profile_mode)) {
> +		if (pfdev->profile_mode) {
>  			panfrost_cycle_counter_get(pfdev);
>  			job->is_profiled = true;
>  			job->start_time = ktime_get();