[Intel-gfx] [RFC 1/1] drm/i915/dgfx: Handling of pin_map against rpm

[Anshuman Gupta <anshuman.gupta@intel.com>]

If i915 gem obj lies in lmem, then i915_gem_object_pin_map
need to grab a rpm wakeref to make sure gfx PCIe endpoint
function stays in D0 state during any access to mapping
returned by i915_gem_object_pin_map().
Subsequently i915_gem_object_upin_map will put the wakref as well.

Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_object.c       |  2 ++
 drivers/gpu/drm/i915/gem/i915_gem_object.h       |  5 +++++
 drivers/gpu/drm/i915/gem/i915_gem_object_types.h | 14 ++++++++++++++
 drivers/gpu/drm/i915/gem/i915_gem_pages.c        |  8 ++++++++
 4 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
index 85482a04d158..f291f990838d 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
@@ -95,6 +95,7 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
 	mutex_init(&obj->mm.get_page.lock);
 	INIT_RADIX_TREE(&obj->mm.get_dma_page.radix, GFP_KERNEL | __GFP_NOWARN);
 	mutex_init(&obj->mm.get_dma_page.lock);
+	mutex_init(&obj->wakeref_lock);
 }
 
 /**
@@ -110,6 +111,7 @@ void __i915_gem_object_fini(struct drm_i915_gem_object *obj)
 {
 	mutex_destroy(&obj->mm.get_page.lock);
 	mutex_destroy(&obj->mm.get_dma_page.lock);
+	mutex_destroy(&obj->wakeref_lock);
 	dma_resv_fini(&obj->base._resv);
 }
 
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index 7317d4102955..b31ac6e4c272 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -501,6 +501,11 @@ static inline void i915_gem_object_flush_map(struct drm_i915_gem_object *obj)
  */
 static inline void i915_gem_object_unpin_map(struct drm_i915_gem_object *obj)
 {
+	mutext_lock(obj->wakeref_lock);
+	if (!--obj->wakeref_count)
+		intel_runtime_pm_put(&to_i915(obj->base.dev)->runtime_pm, obj->wakeref);
+	mutext_unlock(obj->wakeref_lock);
+
 	i915_gem_object_unpin_pages(obj);
 }
 
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 9f6b14ec189a..34aff95a1984 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -657,6 +657,20 @@ struct drm_i915_gem_object {
 
 		void *gvt_info;
 	};
+
+	/**
+	 * wakeref to protect the i915 lmem iomem mappings.
+	 * We don't pin_map an object partially that makes easy
+	 * to track the wakeref cookie, if wakeref is already held
+	 * then we don't need to grab it again for other pin_map.
+	 * first pin_map will grab the wakeref and last unpin_map
+	 * will put the wakeref.
+	 */
+	intel_wakeref_t wakeref;
+	unsigned int wakeref_count;
+
+	/** protects the wakeref_count wakeref cookie against multiple pin_map and unpin_map */
+	struct mutex wakeref_lock;
 };
 
 static inline struct drm_i915_gem_object *
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index 4df50b049cea..b638b5413280 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -370,6 +370,14 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 
 	assert_object_held(obj);
 
+	if (i915_gem_object_is_lmem(obj)) {
+		mutex_lock(&obj->wakeref_lock);
+		if (!obj->wakeref_count++)
+			obj->wakeref =
+				intel_runtime_pm_get(&to_i915(obj->base.dev)->runtime_pm);
+		mutex_unlock(&obj->wakeref_lock);
+	}
+
 	pinned = !(type & I915_MAP_OVERRIDE);
 	type &= ~I915_MAP_OVERRIDE;
 
-- 
2.26.2