Re: [PATCH 3/3] drm/panfrost: show device-wide list of DRM GEM objects over DebugFS

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 24 Apr 2025 03:21:32 +0100
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:

> This change is essentially a Panfrost port of commit a3707f53eb3f
> ("drm/panthor: show device-wide list of DRM GEM objects over DebugFS").
> 
> The DebugFS file is almost the same as in Panthor, minus the GEM object
> usage flags, since Panfrost has no kernel-only BO's.
> 
> Two additional GEM state flags which are displayed but aren't relevant
> to Panthor are 'Purged' and 'Purgeable', since Panfrost implements an
> explicit shrinker and a madvise ioctl to flag objects as reclaimable.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_device.c |   4 +
>  drivers/gpu/drm/panfrost/panfrost_device.h |  11 ++
>  drivers/gpu/drm/panfrost/panfrost_drv.c    |  37 ++++++
>  drivers/gpu/drm/panfrost/panfrost_gem.c    | 137 +++++++++++++++++++++
>  drivers/gpu/drm/panfrost/panfrost_gem.h    |  58 +++++++++
>  5 files changed, 247 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index a45e4addcc19..7ba140aaf59d 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> @@ -209,6 +209,10 @@ int panfrost_device_init(struct panfrost_device *pfdev)
>  
>  	spin_lock_init(&pfdev->cycle_counter.lock);
>  
> +#ifdef CONFIG_DEBUG_FS
> +	mutex_init(&pfdev->gems.lock);
> +	INIT_LIST_HEAD(&pfdev->gems.node);
> +#endif
>  	err = panfrost_clk_init(pfdev);
>  	if (err) {
>  		dev_err(pfdev->dev, "clk init failed %d\n", err);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index ad95f2ed31d9..395272a79306 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -161,6 +161,17 @@ struct panfrost_device {
>  		atomic_t use_count;
>  		spinlock_t lock;
>  	} cycle_counter;
> +
> +	#ifdef CONFIG_DEBUG_FS

Drop the tab.

> +	/** @gems: Device-wide list of GEM objects owned by at least one file. */
> +	struct {
> +		/** @gems.lock: Protects the device-wide list of GEM objects. */
> +		struct mutex lock;
> +
> +		/** @node: Used to keep track of all the device's DRM objects */
> +		struct list_head node;
> +	} gems;
> +#endif

I would probably also put those in a panfrost_device_debugfs struct.

>  };
>  
>  struct panfrost_mmu {
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index b0ab76d67e96..12dd9f311984 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -13,6 +13,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
>  #include <drm/panfrost_drm.h>
> +#include <drm/drm_debugfs.h>
>  #include <drm/drm_drv.h>
>  #include <drm/drm_ioctl.h>
>  #include <drm/drm_syncobj.h>
> @@ -153,6 +154,8 @@ static int panfrost_ioctl_create_bo(struct drm_device *dev, void *data,
>  		ret = -EINVAL;
>  	}
>  
> +	panfrost_gem_debugfs_init_bo(bo);

This is the only place where you call panfrost_gem_debugfs_init_bo(),
so why not calling panfrost_gem_debugfs_bo_add() at the end of
panfrost_gem_create() instead, and drop the initialised field (and
panfrost_gem_debugfs_init_bo() helper).

> +
>  out:
>  	drm_gem_object_put(&bo->base.base);
>  	return ret;
> @@ -659,6 +662,37 @@ static const struct file_operations panfrost_drm_driver_fops = {
>  	.show_fdinfo = drm_show_fdinfo,
>  };
>  
> +#ifdef CONFIG_DEBUG_FS
> +static int panthor_gems_show(struct seq_file *m, void *data)
> +{
> +	struct drm_info_node *node = m->private;
> +	struct drm_device *dev = node->minor->dev;
> +	struct panfrost_device *pfdev = dev->dev_private;
> +
> +	panfrost_gem_debugfs_print_bos(pfdev, m);
> +
> +	return 0;
> +}
> +
> +static struct drm_info_list panthor_debugfs_list[] = {
> +	{"gems", panthor_gems_show, 0, NULL},
> +};
> +
> +static int panthor_gems_debugfs_init(struct drm_minor *minor)
> +{
> +	drm_debugfs_create_files(panthor_debugfs_list,
> +				 ARRAY_SIZE(panthor_debugfs_list),
> +				 minor->debugfs_root, minor);
> +
> +	return 0;
> +}
> +
> +static void panfrost_debugfs_init(struct drm_minor *minor)
> +{
> +	panthor_gems_debugfs_init(minor);
> +}
> +#endif
> +
>  /*
>   * Panfrost driver version:
>   * - 1.0 - initial interface
> @@ -683,6 +717,9 @@ 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)
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index a7a29974d8b1..8a0fd1abd05c 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -12,6 +12,38 @@
>  #include "panfrost_gem.h"
>  #include "panfrost_mmu.h"
>  
> +#ifdef CONFIG_DEBUG_FS
> +static void panfrost_gem_debugfs_bo_add(struct panfrost_device *ptdev,
> +					struct panfrost_gem_object *bo)
> +{
> +	INIT_LIST_HEAD(&bo->debugfs.node);

There's no point calling INIT_LIST_HEAD() if you're calling
list_add_tail() immediately after.

> +
> +	bo->debugfs.creator.tgid = current->group_leader->pid;
> +	get_task_comm(bo->debugfs.creator.process_name, current->group_leader);
> +
> +	mutex_lock(&ptdev->gems.lock);
> +	list_add_tail(&bo->debugfs.node, &ptdev->gems.node);
> +	mutex_unlock(&ptdev->gems.lock);
> +}
> +
> +static void panfrost_gem_debugfs_bo_rm(struct panfrost_gem_object *bo)
> +{
> +	struct panfrost_device *ptdev = bo->base.base.dev->dev_private;
> +
> +	if (list_empty(&bo->debugfs.node))
> +		return;
> +
> +	mutex_lock(&ptdev->gems.lock);
> +	list_del_init(&bo->debugfs.node);
> +	mutex_unlock(&ptdev->gems.lock);
> +}
> +#else
> +static void panfrost_gem_debugfs_bo_add(struct panfrost_device *ptdev,
> +					struct panfrost_gem_object *bo)
> +{}
> +static void panfrost_gem_debugfs_bo_rm(struct panfrost_gem_object *bo) {}
> +#endif
> +
>  /* Called DRM core on the last userspace/kernel unreference of the
>   * BO.
>   */
> @@ -36,6 +68,7 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
>  	 */
>  	WARN_ON_ONCE(!list_empty(&bo->mappings.list));
>  
> +	panfrost_gem_debugfs_bo_rm(bo);
>  	kfree(bo->label.str);
>  	mutex_destroy(&bo->label.lock);
>  
> @@ -266,6 +299,8 @@ struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t
>  	obj->base.map_wc = !pfdev->coherent;
>  	mutex_init(&obj->label.lock);
>  
> +	panfrost_gem_debugfs_bo_add(pfdev, obj);
> +
>  	return &obj->base.base;
>  }
>  
> @@ -321,3 +356,105 @@ panfrost_gem_set_label(struct drm_gem_object *obj, const char *label)
>  
>  	kfree(old_label);
>  }
> +
> +#ifdef CONFIG_DEBUG_FS
> +struct gem_size_totals {
> +	size_t size;
> +	size_t resident;
> +	size_t reclaimable;
> +};
> +
> +struct flag_def {
> +	u32 flag;
> +	const char *name;
> +};
> +
> +static void panfrost_gem_debugfs_print_flag_names(struct seq_file *m)
> +{
> +	int len;
> +	int i;
> +
> +	static const struct flag_def gem_state_flags_names[] = {
> +		{PANFROST_DEBUGFS_GEM_STATE_FLAG_IMPORTED, "imported"},
> +		{PANFROST_DEBUGFS_GEM_STATE_FLAG_EXPORTED, "exported"},
> +		{PANFROST_DEBUGFS_GEM_STATE_FLAG_PURGED, "purged"},
> +		{PANFROST_DEBUGFS_GEM_STATE_FLAG_PURGEABLE, "purgeable"},
> +	};
> +
> +	seq_puts(m, "GEM state flags: ");
> +	for (i = 0, len = ARRAY_SIZE(gem_state_flags_names); i < len; i++) {
> +		seq_printf(m, "%s (0x%x)%s", gem_state_flags_names[i].name,
> +			   gem_state_flags_names[i].flag, (i < len - 1) ? ", " : "\n\n");
> +	}
> +}
> +
> +static void panfrost_gem_debugfs_bo_print(struct panfrost_gem_object *bo,
> +					  struct seq_file *m,
> +					  struct gem_size_totals *totals)
> +{
> +	unsigned int refcount = kref_read(&bo->base.base.refcount);
> +	char creator_info[32] = {};
> +	size_t resident_size;
> +	u32 gem_state_flags = 0;
> +
> +	/* Skip BOs being destroyed. */
> +	if (!refcount)
> +		return;
> +
> +	resident_size = bo->base.pages ? bo->base.base.size : 0;
> +
> +	snprintf(creator_info, sizeof(creator_info),
> +		 "%s/%d", bo->debugfs.creator.process_name, bo->debugfs.creator.tgid);
> +	seq_printf(m, "%-32s%-16d%-16d%-16zd%-16zd0x%-16lx",
> +		   creator_info,
> +		   bo->base.base.name,
> +		   refcount,
> +		   bo->base.base.size,
> +		   resident_size,
> +		   drm_vma_node_start(&bo->base.base.vma_node));
> +
> +	if (bo->base.base.import_attach)
> +		gem_state_flags |= PANFROST_DEBUGFS_GEM_STATE_FLAG_IMPORTED;
> +	if (bo->base.base.dma_buf)
> +		gem_state_flags |= PANFROST_DEBUGFS_GEM_STATE_FLAG_EXPORTED;
> +
> +	if (bo->base.madv < 0)
> +		gem_state_flags |= PANFROST_DEBUGFS_GEM_STATE_FLAG_PURGED;
> +	else if (bo->base.madv > 0)
> +		gem_state_flags |= PANFROST_DEBUGFS_GEM_STATE_FLAG_PURGEABLE;
> +
> +	seq_printf(m, "0x%-10x", gem_state_flags);
> +
> +	scoped_guard(mutex, &bo->label.lock) {
> +		seq_printf(m, "%s\n", bo->label.str ? : "");
> +	}
> +
> +	totals->size += bo->base.base.size;
> +	totals->resident += resident_size;
> +	if (bo->base.madv > 0)
> +		totals->reclaimable += resident_size;
> +}
> +
> +void panfrost_gem_debugfs_print_bos(struct panfrost_device *ptdev,
> +				    struct seq_file *m)
> +{
> +	struct gem_size_totals totals = {0};
> +	struct panfrost_gem_object *bo;
> +
> +	panfrost_gem_debugfs_print_flag_names(m);
> +
> +	seq_puts(m, "created-by                      global-name     refcount        size            resident-size   file-offset       state       label\n");
> +	seq_puts(m, "-----------------------------------------------------------------------------------------------------------------------------------\n");
> +
> +	scoped_guard(mutex, &ptdev->gems.lock) {
> +		list_for_each_entry(bo, &ptdev->gems.node, debugfs.node) {
> +			if (bo->debugfs.initialised)
> +				panfrost_gem_debugfs_bo_print(bo, m, &totals);
> +		}
> +	}
> +
> +	seq_puts(m, "===================================================================================================================================\n");
> +	seq_printf(m, "Total size: %zd, Total resident: %zd, Total reclaimable: %zd\n",
> +		   totals.size, totals.resident, totals.reclaimable);
> +}
> +#endif
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> index 842e025b9bdc..bc60e0d74da9 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> @@ -8,9 +8,50 @@
>  #include <drm/drm_mm.h>
>  
>  struct panfrost_mmu;
> +struct panfrost_device;
>  
>  #define PANFROST_BO_LABEL_MAXLEN	4096
>  
> +enum panfrost_debugfs_gem_state_flags {
> +	/** @PANFROST_DEBUGFS_GEM_STATE_FLAG_IMPORTED: GEM BO is PRIME imported. */
> +	PANFROST_DEBUGFS_GEM_STATE_FLAG_IMPORTED = BIT(0),
> +
> +	/** @PANFROST_DEBUGFS_GEM_STATE_FLAG_EXPORTED: GEM BO is PRIME exported. */
> +	PANFROST_DEBUGFS_GEM_STATE_FLAG_EXPORTED = BIT(1),
> +
> +	/** @PANFROST_DEBUGFS_GEM_STATE_FLAG_PURGED: GEM BO was reclaimed by the shrinker. */
> +	PANFROST_DEBUGFS_GEM_STATE_FLAG_PURGED = BIT(2),
> +
> +	/**
> +	 * @PANFROST_DEBUGFS_GEM_STATE_FLAG_PURGEABLE: GEM BO pages were marked as no longer
> +	 * needed by UM and can be reclaimed by the shrinker.
> +	 */
> +	PANFROST_DEBUGFS_GEM_STATE_FLAG_PURGEABLE = BIT(3),
> +};
> +
> +/**
> + * struct panfrost_gem_debugfs - GEM object's DebugFS list information
> + */
> +struct panfrost_gem_debugfs {
> +	/**
> +	 * @node: Node used to insert the object in the device-wide list of
> +	 * GEM objects, to display information about it through a DebugFS file.
> +	 */
> +	struct list_head node;
> +
> +	/** @creator: Information about the UM process which created the GEM. */
> +	struct {
> +		/** @creator.process_name: Group leader name in owning thread's process */
> +		char process_name[TASK_COMM_LEN];
> +
> +		/** @creator.tgid: PID of the thread's group leader within its process */
> +		pid_t tgid;
> +	} creator;
> +
> +	/** @initialised: GEM object is ready to be displayed in DebugFS file. */
> +	bool initialised;
> +};
> +
>  struct panfrost_gem_object {
>  	struct drm_gem_shmem_object base;
>  	struct sg_table *sgts;
> @@ -59,6 +100,10 @@ struct panfrost_gem_object {
>  
>  	bool noexec		:1;
>  	bool is_heap		:1;
> +
> +#ifdef CONFIG_DEBUG_FS
> +	struct panfrost_gem_debugfs debugfs;
> +#endif
>  };
>  
>  struct panfrost_gem_mapping {
> @@ -107,4 +152,17 @@ void panfrost_gem_shrinker_cleanup(struct drm_device *dev);
>  
>  void panfrost_gem_set_label(struct drm_gem_object *obj, const char *label);
>  
> +#ifdef CONFIG_DEBUG_FS
> +void panfrost_gem_debugfs_print_bos(struct panfrost_device *pfdev,
> +				    struct seq_file *m);
> +static inline void
> +panfrost_gem_debugfs_init_bo(struct panfrost_gem_object *bo)
> +{
> +	bo->debugfs.initialised = true;
> +}
> +#else
> +static inline void
> +panfrost_gem_debugfs_init_bo(struct panfrost_gem_object *bo) {};
> +#endif
> +
>  #endif /* __PANFROST_GEM_H__ */