[Intel-gfx] [RFC 1/2] drm/i915: Move ioremap_wc tracking onto VMA

[Tvrtko Ursulin]

From: Chris Wilson <chris at chris-wilson.co.uk>

By tracking the iomapping on the VMA itself, we can share that area
between multiple users. Also by only revoking the iomapping upon
unbinding from the mappable portion of the GGTT, we can keep that iomap
across multiple invocations (e.g. execlists context pinning).

v2:
  * Rebase on nightly;
  * added kerneldoc. (Tvrtko Ursulin)

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c     |  2 ++
 drivers/gpu/drm/i915/i915_gem_gtt.c | 38 +++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem_gtt.h | 38 +++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_fbdev.c  |  8 +++-----
 4 files changed, 81 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b37ffea8b458..6a485630595e 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3393,6 +3393,8 @@ static int __i915_vma_unbind(struct i915_vma *vma, bool wait)
 		ret = i915_gem_object_put_fence(obj);
 		if (ret)
 			return ret;
+
+		i915_vma_iounmap(vma);
 	}
 
 	trace_i915_vma_unbind(vma);
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index c5cb04907525..b2a8a14e8dcb 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3626,3 +3626,41 @@ i915_ggtt_view_size(struct drm_i915_gem_object *obj,
 		return obj->base.size;
 	}
 }
+
+void *i915_vma_iomap(struct drm_i915_private *dev_priv,
+		     struct i915_vma *vma)
+{
+	struct drm_i915_gem_object *obj = vma->obj;
+	struct i915_ggtt *ggtt = &dev_priv->ggtt;
+
+	if (WARN_ON(!obj->map_and_fenceable))
+		return ERR_PTR(-ENODEV);
+
+	BUG_ON(!vma->is_ggtt);
+	BUG_ON(vma->ggtt_view.type != I915_GGTT_VIEW_NORMAL);
+	BUG_ON((vma->bound & GLOBAL_BIND) == 0);
+
+	if (vma->iomap == NULL) {
+		void *ptr;
+
+		ptr = ioremap_wc(ggtt->mappable_base + vma->node.start,
+				 obj->base.size);
+		if (ptr == NULL) {
+			int ret;
+
+			/* Too many areas already allocated? */
+			ret = i915_gem_evict_vm(vma->vm, true);
+			if (ret)
+				return ERR_PTR(ret);
+
+			ptr = ioremap_wc(ggtt->mappable_base + vma->node.start,
+					 obj->base.size);
+			if (ptr == NULL)
+				return ERR_PTR(-ENOMEM);
+		}
+
+		vma->iomap = ptr;
+	}
+
+	return vma->iomap;
+}
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index d7dd3d8a8758..526fdbc71ace 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -175,6 +175,7 @@ struct i915_vma {
 	struct drm_mm_node node;
 	struct drm_i915_gem_object *obj;
 	struct i915_address_space *vm;
+	void *iomap;
 
 	/** Flags and address space this VMA is bound to */
 #define GLOBAL_BIND	(1<<0)
@@ -559,4 +560,41 @@ size_t
 i915_ggtt_view_size(struct drm_i915_gem_object *obj,
 		    const struct i915_ggtt_view *view);
 
+/**
+ * i915_vma_iomap - calls ioremap_wc to map the GGTT VMA via the aperture
+ * @dev_priv: i915 private pointer
+ * @vma: VMA to iomap
+ *
+ * The passed in VMA has to be pinned in the global GTT mappable region. Or in
+ * other words callers are responsible for managing the VMA pinned lifetime and
+ * ensuring it covers the use of the returned mapping.
+ *
+ * Callers must hold the struct_mutex.
+ *
+ * Returns a valid iomapped pointer or ERR_PTR.
+ */
+void *i915_vma_iomap(struct drm_i915_private *dev_priv,
+		     struct i915_vma *vma);
+
+/**
+ * i915_vma_iounmap - unmaps the mapping returned from i915_vma_iomap
+ * @dev_priv: i915 private pointer
+ * @vma: VMA to unmap
+ *
+ * Unmaps the previously iomapped VMA using iounmap.
+ *
+ * Users of i915_vma_iomap should not manually unmap by calling this function
+ * if they want to take advantage of the mapping getting cached in the VMA.
+ *
+ * Callers must hold the struct_mutex.
+ */
+static inline void i915_vma_iounmap(struct i915_vma *vma)
+{
+	if (vma->iomap == NULL)
+		return;
+
+	iounmap(vma->iomap);
+	vma->iomap = NULL;
+}
+
 #endif
diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
index 79ac202f3870..515a2214827e 100644
--- a/drivers/gpu/drm/i915/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/intel_fbdev.c
@@ -251,12 +251,10 @@ static int intelfb_create(struct drm_fb_helper *helper,
 	info->fix.smem_start = dev->mode_config.fb_base + i915_gem_obj_ggtt_offset(obj);
 	info->fix.smem_len = size;
 
-	info->screen_base =
-		ioremap_wc(ggtt->mappable_base + i915_gem_obj_ggtt_offset(obj),
-			   size);
-	if (!info->screen_base) {
+	info->screen_base = i915_vma_iomap(dev_priv, i915_gem_obj_to_ggtt(obj));
+	if (IS_ERR(info->screen_base)) {
 		DRM_ERROR("Failed to remap framebuffer into virtual memory\n");
-		ret = -ENOSPC;
+		ret = PTR_ERR(info->screen_base);
 		goto out_destroy_fbi;
 	}
 	info->screen_size = size;
-- 
1.9.1