[PATCH 08/29] drm/i915: Introduce struct intel_wakeref

[Chris Wilson <chris@chris-wilson.co.uk>]

For controlling runtime pm of the GT and engines, we would like to have
a callback to do extra work the first time we wake up and the last time
we drop the wakeref. This first/last access needs serialisation and so
we encompass a mutex with the regular intel_wakeref_t tracker.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/Makefile             |  1 +
 drivers/gpu/drm/i915/Makefile.header-test |  3 +-
 drivers/gpu/drm/i915/i915_drv.h           |  3 +-
 drivers/gpu/drm/i915/intel_wakeref.c      | 51 +++++++++++++++
 drivers/gpu/drm/i915/intel_wakeref.h      | 77 +++++++++++++++++++++++
 5 files changed, 132 insertions(+), 3 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/intel_wakeref.c
 create mode 100644 drivers/gpu/drm/i915/intel_wakeref.h

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 40130cf5c003..233bad5e361f 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -50,6 +50,7 @@ i915-y += i915_drv.o \
 	  intel_device_info.o \
 	  intel_pm.o \
 	  intel_runtime_pm.o \
+	  intel_wakeref.o \
 	  intel_uncore.o
 
 # core library code
diff --git a/drivers/gpu/drm/i915/Makefile.header-test b/drivers/gpu/drm/i915/Makefile.header-test
index 96a5d90629ec..e6b3e7588860 100644
--- a/drivers/gpu/drm/i915/Makefile.header-test
+++ b/drivers/gpu/drm/i915/Makefile.header-test
@@ -31,7 +31,8 @@ header_test := \
 	intel_psr.h \
 	intel_sdvo.h \
 	intel_sprite.h \
-	intel_tv.h
+	intel_tv.h \
+	intel_wakeref.h
 
 quiet_cmd_header_test = HDRTEST $@
       cmd_header_test = echo "\#include \"$(<F)\"" > $@
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index fad5306f07da..62a7e91acd7f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -74,6 +74,7 @@
 #include "intel_opregion.h"
 #include "intel_uc.h"
 #include "intel_uncore.h"
+#include "intel_wakeref.h"
 #include "intel_wopcm.h"
 
 #include "i915_gem.h"
@@ -134,8 +135,6 @@ bool i915_error_injected(void);
 	__i915_printk(i915, i915_error_injected() ? KERN_DEBUG : KERN_ERR, \
 		      fmt, ##__VA_ARGS__)
 
-typedef depot_stack_handle_t intel_wakeref_t;
-
 enum hpd_pin {
 	HPD_NONE = 0,
 	HPD_TV = HPD_NONE,     /* TV is known to be unreliable */
diff --git a/drivers/gpu/drm/i915/intel_wakeref.c b/drivers/gpu/drm/i915/intel_wakeref.c
new file mode 100644
index 000000000000..c133c91cf277
--- /dev/null
+++ b/drivers/gpu/drm/i915/intel_wakeref.c
@@ -0,0 +1,51 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include "intel_drv.h"
+#include "intel_wakeref.h"
+
+void __intel_wakeref_get_once(struct drm_i915_private *i915,
+			      struct intel_wakeref_count *wc,
+			      bool (*fn)(struct intel_wakeref_count *wc))
+{
+	/*
+	 * Treat get/put as different subclasses, as we may need to run
+	 * the put callback from under the shrinker and do not want to
+	 * cross-contanimate that callback with any extra work performed
+	 * upon acquiring the wakeref.
+	 */
+	mutex_lock_nested(&wc->mutex, SINGLE_DEPTH_NESTING);
+	if (!atomic_read(&wc->count)) {
+		wc->wakeref = intel_runtime_pm_get(i915);
+		if (unlikely(!fn(wc))) {
+			intel_runtime_pm_put(i915, wc->wakeref);
+			mutex_unlock(&wc->mutex);
+			return;
+		}
+
+		smp_mb__before_atomic(); /* release wc->count */
+	}
+	atomic_inc(&wc->count);
+	mutex_unlock(&wc->mutex);
+}
+
+void __intel_wakeref_put_once(struct drm_i915_private *i915,
+			      struct intel_wakeref_count *wc,
+			      bool (*fn)(struct intel_wakeref_count *wc))
+{
+	if (likely(fn(wc)))
+		intel_runtime_pm_put(i915, wc->wakeref);
+	else
+		atomic_inc(&wc->count);
+	mutex_unlock(&wc->mutex);
+}
+
+void __intel_wakeref_init(struct intel_wakeref_count *wc,
+			  struct lock_class_key *key)
+{
+	__mutex_init(&wc->mutex, "wakeref", key);
+	atomic_set(&wc->count, 0);
+}
diff --git a/drivers/gpu/drm/i915/intel_wakeref.h b/drivers/gpu/drm/i915/intel_wakeref.h
new file mode 100644
index 000000000000..cd4d8f57e502
--- /dev/null
+++ b/drivers/gpu/drm/i915/intel_wakeref.h
@@ -0,0 +1,77 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2019 Intel Corporation
+ */
+
+#ifndef INTEL_WAKEREF_H
+#define INTEL_WAKEREF_H
+
+#include <linux/atomic.h>
+#include <linux/mutex.h>
+#include <linux/stackdepot.h>
+
+struct drm_i915_private;
+
+typedef depot_stack_handle_t intel_wakeref_t;
+
+struct intel_wakeref_count {
+	atomic_t count;
+	struct mutex mutex;
+	intel_wakeref_t wakeref;
+};
+
+void __intel_wakeref_init(struct intel_wakeref_count *wc,
+			  struct lock_class_key *key);
+#define intel_wakeref_init(wc) do {					\
+	static struct lock_class_key __key;				\
+									\
+	__intel_wakeref_init((wc), &__key);				\
+} while (0)
+
+void __intel_wakeref_get_once(struct drm_i915_private *i915,
+			      struct intel_wakeref_count *wc,
+			      bool (*fn)(struct intel_wakeref_count *wc));
+void __intel_wakeref_put_once(struct drm_i915_private *i915,
+			      struct intel_wakeref_count *wc,
+			      bool (*fn)(struct intel_wakeref_count *wc));
+
+static inline void
+intel_wakeref_get_once(struct drm_i915_private *i915,
+		       struct intel_wakeref_count *wc,
+		       bool (*fn)(struct intel_wakeref_count *wc))
+{
+	if (unlikely(!atomic_inc_not_zero(&wc->count)))
+		__intel_wakeref_get_once(i915, wc, fn);
+}
+
+static inline void
+intel_wakeref_put_once(struct drm_i915_private *i915,
+		       struct intel_wakeref_count *wc,
+		       bool (*fn)(struct intel_wakeref_count *wc))
+{
+	if (atomic_dec_and_mutex_lock(&wc->count, &wc->mutex))
+		__intel_wakeref_put_once(i915, wc, fn);
+}
+
+static inline void
+intel_wakeref_lock(struct intel_wakeref_count *wc)
+	__acquires(wc->mutex)
+{
+	mutex_lock(&wc->mutex);
+}
+
+static inline void
+intel_wakeref_unlock(struct intel_wakeref_count *wc)
+	__releases(wc->mutex)
+{
+	mutex_unlock(&wc->mutex);
+}
+
+static inline bool
+intel_wakeref_active(struct intel_wakeref_count *wc)
+{
+	return atomic_read(&wc->count);
+}
+
+#endif /* INTEL_WAKEREF_H */
-- 
2.20.1

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