On 09/12/15 12:46, ankitprasad.r.sharma@xxxxxxxxx wrote:
From: Ankitprasad Sharma <ankitprasad.r.sharma@xxxxxxxxx>
This patch adds support for clearing buffer objects via CPU/GTT. This
is particularly useful for clearing out the non shmem backed objects.
Currently intend to use this only for buffers allocated from stolen
region.
v2: Added kernel doc for i915_gem_clear_object(), corrected/removed
variable assignments (Tvrtko)
v3: Map object page by page to the gtt if the pinning of the whole object
to the ggtt fails, Corrected function name (Chris)
Testcase: igt/gem_stolen
Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@xxxxxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.h | 1 +
drivers/gpu/drm/i915/i915_gem.c | 79 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 80 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 548a0eb..8e554d3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2856,6 +2856,7 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj,
int *needs_clflush);
int __must_check i915_gem_object_get_pages(struct drm_i915_gem_object *obj);
+int i915_gem_object_clear(struct drm_i915_gem_object *obj);
static inline int __sg_page_count(struct scatterlist *sg)
{
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9d2e6e3..d57e850 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5244,3 +5244,82 @@ fail:
drm_gem_object_unreference(&obj->base);
return ERR_PTR(ret);
}
+
+/**
+ * i915_gem_clear_object() - Clear buffer object via CPU/GTT
+ * @obj: Buffer object to be cleared
+ *
+ * Return: 0 - success, non-zero - failure
+ */
+int i915_gem_object_clear(struct drm_i915_gem_object *obj)
+{
+ int ret, i;
+ char __iomem *base;
+ size_t size = obj->base.size;
+ struct drm_i915_private *i915 = to_i915(obj->base.dev);
+ struct drm_mm_node node;
+
+ WARN_ON(!mutex_is_locked(&obj->base.dev->struct_mutex));
+ ret = i915_gem_obj_ggtt_pin(obj, 0, PIN_MAPPABLE | PIN_NONBLOCK);
Hm, I thought Chrises suggestion was not to even try mapping all of it
into GTT but just go page by page?
If I misunderstood that then I agree with Dave's comment that it should
be split in two helper functions.
+ if (ret) {
+ memset(&node, 0, sizeof(node));
+ ret = drm_mm_insert_node_in_range_generic(&i915->gtt.base.mm,
+ &node, 4096, 0,
+ I915_CACHE_NONE, 0,
+ i915->gtt.mappable_end,
+ DRM_MM_SEARCH_DEFAULT,
+ DRM_MM_CREATE_DEFAULT);
+ if (ret)
+ goto out;
+
+ i915_gem_object_pin_pages(obj);
+ } else {
+ node.start = i915_gem_obj_ggtt_offset(obj);
+ node.allocated = false;
This looks very hacky anyway and I would not recommend it.
+ }
+
+ ret = i915_gem_object_put_fence(obj);
+ if (ret)
+ goto unpin;
+
+ if (node.allocated) {
+ for (i = 0; i < size/PAGE_SIZE; i++) {
+ wmb();
What is this barreier for? Shouldn't the one after writting out the PTEs
and before remapping be enough?
+ i915->gtt.base.insert_page(&i915->gtt.base,
+ i915_gem_object_get_dma_address(obj, i),
+ node.start,
+ I915_CACHE_NONE,
+ 0);
+ wmb();
+ base = ioremap_wc(i915->gtt.mappable_base + node.start, 4096);
+ memset_io(base, 0, 4096);
+ iounmap(base);
+ }
+ } else {
+ /* Get the CPU virtual address of the buffer */
+ base = ioremap_wc(i915->gtt.mappable_base +
+ node.start, size);
+ if (base == NULL) {
+ DRM_ERROR("Mapping of gem object to CPU failed!\n");
+ ret = -ENOSPC;
+ goto unpin;
+ }
+
+ memset_io(base, 0, size);
+ iounmap(base);
+ }
+unpin:
+ if (node.allocated) {
+ wmb();
I don't understand this one either?
+ i915->gtt.base.clear_range(&i915->gtt.base,
+ node.start, node.size,
+ true);
+ drm_mm_remove_node(&node);
+ i915_gem_object_unpin_pages(obj);
+ }
+ else {
+ i915_gem_object_ggtt_unpin(obj);
+ }
+out:
+ return ret;
+}
Regards,
Tvrtko
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