drm/i915/perf: Register sysctl path globally

We do not require to register the sysctl paths per instance,
so making registration global.

v2: make sysctl path register and unregister function driver
    specific (Tvrtko and Lucas).

Cc: Sudeep Dutt <sudeep.dutt@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191213155152.69182-1-venkata.s.dhanalakota@intel.com

drivers/gpu/drm/i915/i915_pci.c

@@ -30,6 +30,7 @@
 #include "display/intel_fbdev.h"
 
 #include "i915_drv.h"
+#include "i915_perf.h"
 #include "i915_globals.h"
 #include "i915_selftest.h"
 
@@ -1053,7 +1054,12 @@ static int __init i915_init(void)
 		return 0;
 	}
 
-	return pci_register_driver(&i915_pci_driver);
+	err = pci_register_driver(&i915_pci_driver);
+	if (err)
+		return err;
+
+	i915_perf_sysctl_register();
+	return 0;
 }
 
 static void __exit i915_exit(void)
@@ -1061,6 +1067,7 @@ static void __exit i915_exit(void)
 	if (!i915_pci_driver.driver.owner)
 		return;
 
+	i915_perf_sysctl_unregister();
 	pci_unregister_driver(&i915_pci_driver);
 	i915_globals_exit();
 }

drivers/gpu/drm/i915/i915_perf.c

@@ -387,6 +387,8 @@ struct i915_oa_config_bo {
 	struct i915_vma *vma;
 };
 
+static struct ctl_table_header *sysctl_header;
+
 static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer);
 
 void i915_oa_config_release(struct kref *ref)
@@ -4228,7 +4230,7 @@ static struct ctl_table dev_root[] = {
 };
 
 /**
- * i915_perf_init - initialize i915-perf state on module load
+ * i915_perf_init - initialize i915-perf state on module bind
  * @i915: i915 device instance
  *
  * Initializes i915-perf state without exposing anything to userspace.
@@ -4345,7 +4347,6 @@ void i915_perf_init(struct drm_i915_private *i915)
 
 		oa_sample_rate_hard_limit = 1000 *
 			(RUNTIME_INFO(i915)->cs_timestamp_frequency_khz / 2);
-		perf->sysctl_header = register_sysctl_table(dev_root);
 
 		mutex_init(&perf->metrics_lock);
 		idr_init(&perf->metrics_idr);
@@ -4381,6 +4382,16 @@ static int destroy_config(int id, void *p, void *data)
 	return 0;
 }
 
+void i915_perf_sysctl_register(void)
+{
+	sysctl_header = register_sysctl_table(dev_root);
+}
+
+void i915_perf_sysctl_unregister(void)
+{
+	unregister_sysctl_table(sysctl_header);
+}
+
 /**
  * i915_perf_fini - Counter part to i915_perf_init()
  * @i915: i915 device instance
@@ -4395,8 +4406,6 @@ void i915_perf_fini(struct drm_i915_private *i915)
 	idr_for_each(&perf->metrics_idr, destroy_config, perf);
 	idr_destroy(&perf->metrics_idr);
 
-	unregister_sysctl_table(perf->sysctl_header);
-
 	memset(&perf->ops, 0, sizeof(perf->ops));
 	perf->i915 = NULL;
 }

drivers/gpu/drm/i915/i915_perf.h

@@ -23,6 +23,8 @@ void i915_perf_fini(struct drm_i915_private *i915);
 void i915_perf_register(struct drm_i915_private *i915);
 void i915_perf_unregister(struct drm_i915_private *i915);
 int i915_perf_ioctl_version(void);
+void i915_perf_sysctl_register(void);
+void i915_perf_sysctl_unregister(void);
 
 int i915_perf_open_ioctl(struct drm_device *dev, void *data,
 			 struct drm_file *file);

drivers/gpu/drm/i915/i915_perf_types.h

@@ -380,7 +380,6 @@ struct i915_perf {
 	struct drm_i915_private *i915;
 
 	struct kobject *metrics_kobj;
-	struct ctl_table_header *sysctl_header;
 
 	/*
 	 * Lock associated with adding/modifying/removing OA configs