[RFC 06/12] drm/cgroup: Add ability to query drm cgroup GPU time

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Add a driver callback and core helper which allow querying the time spent
on GPUs for processes belonging to a group.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/drm_cgroup.c | 24 ++++++++++++++++++++++++
 include/drm/drm_clients.h    |  2 ++
 include/drm/drm_drv.h        | 28 ++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+)

diff --git a/drivers/gpu/drm/drm_cgroup.c b/drivers/gpu/drm/drm_cgroup.c
index 46b012d2be42..bc1e34f1a552 100644
--- a/drivers/gpu/drm/drm_cgroup.c
+++ b/drivers/gpu/drm/drm_cgroup.c
@@ -138,3 +138,27 @@ drm_clients_migrate(struct drm_file *file_priv,
 		 pid_nr(old), pid_nr(new));
 	rcu_read_unlock();
 }
+
+u64 drm_pid_get_active_time_us(struct pid *pid)
+{
+	struct drm_pid_clients *clients;
+	u64 total = 0;
+
+	rcu_read_lock();
+	clients = xa_load(&drm_pid_clients, (unsigned long)pid);
+	if (clients) {
+		struct drm_file *fpriv;
+
+		list_for_each_entry_rcu(fpriv, &clients->file_list, clink) {
+			const struct drm_cgroup_ops *cg_ops =
+				fpriv->minor->dev->driver->cg_ops;
+
+			if (cg_ops && cg_ops->active_time_us)
+				total += cg_ops->active_time_us(fpriv);
+		}
+	}
+	rcu_read_unlock();
+
+	return total;
+}
+EXPORT_SYMBOL_GPL(drm_pid_get_active_time_us);
diff --git a/include/drm/drm_clients.h b/include/drm/drm_clients.h
index 2732fffab3f0..7e0c0cf14f25 100644
--- a/include/drm/drm_clients.h
+++ b/include/drm/drm_clients.h
@@ -41,4 +41,6 @@ drm_clients_migrate(struct drm_file *file_priv,
 }
 #endif
 
+u64 drm_pid_get_active_time_us(struct pid *pid);
+
 #endif
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index d7c521e8860f..f5f0e088e1fe 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -158,6 +158,24 @@ enum drm_driver_feature {
 	DRIVER_KMS_LEGACY_CONTEXT	= BIT(31),
 };
 
+/**
+ * struct drm_cgroup_ops
+ *
+ * This structure contains a number of callbacks that drivers can provide if
+ * they are able to support one or more of the functionalities implemented by
+ * the DRM cgroup controller.
+ */
+struct drm_cgroup_ops {
+	/**
+	 * @active_time_us:
+	 *
+	 * Optional callback for reporting the GPU time consumed by this client.
+	 *
+	 * Used by the DRM core when queried by the DRM cgroup controller.
+	 */
+	u64 (*active_time_us) (struct drm_file *);
+};
+
 /**
  * struct drm_driver - DRM driver structure
  *
@@ -469,6 +487,16 @@ struct drm_driver {
 	 */
 	const struct file_operations *fops;
 
+#ifdef CONFIG_CGROUP_DRM
+	/**
+	 * @cg_ops:
+	 *
+	 * Optional pointer to driver callbacks facilitating integration with
+	 * the DRM cgroup controller.
+	 */
+	const struct drm_cgroup_ops *cg_ops;
+#endif
+
 #ifdef CONFIG_DRM_LEGACY
 	/* Everything below here is for legacy driver, never use! */
 	/* private: */
-- 
2.34.1