[RFC 3/8] 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>
---
 include/drm/drm_drv.h | 28 ++++++++++++++++++++++++++++
 kernel/cgroup/drm.c   | 20 ++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index e2640dc64e08..d1cee5899cde 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -157,6 +157,24 @@ enum drm_driver_feature {
 	DRIVER_HAVE_IRQ			= BIT(30),
 };
 
+/**
+ * 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
  *
@@ -434,6 +452,16 @@ 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: */
diff --git a/kernel/cgroup/drm.c b/kernel/cgroup/drm.c
index d702be1b441f..acdb76635b60 100644
--- a/kernel/cgroup/drm.c
+++ b/kernel/cgroup/drm.c
@@ -9,6 +9,8 @@
 #include <linux/mutex.h>
 #include <linux/slab.h>
 
+#include <drm/drm_drv.h>
+
 struct drm_cgroup_state {
 	struct cgroup_subsys_state css;
 
@@ -31,6 +33,24 @@ css_to_drmcs(struct cgroup_subsys_state *css)
 	return container_of(css, struct drm_cgroup_state, css);
 }
 
+static u64 drmcs_get_active_time_us(struct drm_cgroup_state *drmcs)
+{
+	struct drm_file *fpriv;
+	u64 total = 0;
+
+	lockdep_assert_held(&drmcg_mutex);
+
+	list_for_each_entry(fpriv, &drmcs->clients, 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);
+	}
+
+	return total;
+}
+
 static void drmcs_free(struct cgroup_subsys_state *css)
 {
 	struct drm_cgroup_state *drmcs = css_to_drmcs(css);
-- 
2.39.2