Add a simple helper to read data with the CPU from the page of a GEM
object. Do the read either via a kmap if the object has struct pages
or an iomap otherwise. This is needed by the next patch, reading a u64
value from the object (w/o requiring the obj to be mapped to the GPU).
Suggested by Chris.
v2 (Chris):
- Sanitize the type and order of func params.
- Avoid consts requiring too many casts.
- Use BUG_ON instead of WARN_ON, simplify the conditions.
- Fix __iomem sparse errors.
- Leave locking/syncing/pinning up to the caller, require only that the
caller has pinned the object pages.
- Check for iomem backing store before reading via an iomap.
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_object.c | 64 ++++++++++++++++++++++
drivers/gpu/drm/i915/gem/i915_gem_object.h | 8 +++
2 files changed, 72 insertions(+)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
index 00d24000b5e8..67956a5f5fe3 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
@@ -32,6 +32,7 @@
#include "i915_gem_mman.h"
#include "i915_gem_object.h"
#include "i915_globals.h"
+#include "i915_memcpy.h"
#include "i915_trace.h"
static struct i915_global_object {
@@ -383,6 +384,69 @@ void __i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj,
}
}
+static void
+i915_gem_object_read_from_page_kmap(struct drm_i915_gem_object *obj, u64 offset, void *dst, int size)
+{
+ void *src_map;
+ void *src_ptr;
+
+ src_map = kmap_atomic(i915_gem_object_get_page(obj, offset >> PAGE_SHIFT));
+
+ src_ptr = src_map + offset_in_page(offset);
+ if (!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ))
+ drm_clflush_virt_range(src_ptr, size);
+ memcpy(dst, src_ptr, size);
+
+ kunmap_atomic(src_map);
+}
+
+static void
+i915_gem_object_read_from_page_iomap(struct drm_i915_gem_object *obj, u64 offset, void *dst, int size)
+{
+ void __iomem *src_map;
+ void __iomem *src_ptr;
+
+ src_map = io_mapping_map_wc(&obj->mm.region->iomap,
+ i915_gem_object_get_dma_address(obj, offset >> PAGE_SHIFT),
+ PAGE_SIZE);
+
+ src_ptr = src_map + offset_in_page(offset);
+ if (!i915_memcpy_from_wc(dst, (void __force *)src_ptr, size))
+ memcpy_fromio(dst, src_ptr, size);
+
+ io_mapping_unmap(src_map);
+}
+
+/**
+ * i915_gem_object_read_from_page - read data from the page of a GEM object
+ * @obj: GEM object to read from
+ * @offset: offset within the object
+ * @dst: buffer to store the read data
+ * @size: size to read
+ *
+ * Reads data from @obj at the specified offset. The requested region to read
+ * from can't cross a page boundary. The caller must ensure that @obj pages
+ * are pinned and that @obj is synced wrt. any related writes.
+ *
+ * Returns 0 on sucess or -ENODEV if the type of @obj's backing store is
+ * unsupported.
+ */
+int i915_gem_object_read_from_page(struct drm_i915_gem_object *obj, u64 offset, void *dst, int size)
+{
+ GEM_BUG_ON(offset >= obj->base.size);
+ GEM_BUG_ON(offset_in_page(offset) > PAGE_SIZE - size);
+ GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
+
+ if (i915_gem_object_has_struct_page(obj))
+ i915_gem_object_read_from_page_kmap(obj, offset, dst, size);
+ else if (i915_gem_object_has_iomem(obj))
+ i915_gem_object_read_from_page_iomap(obj, offset, dst, size);
+ else
+ return -ENODEV;
+
+ return 0;
+}
+
void i915_gem_init__objects(struct drm_i915_private *i915)
{
INIT_WORK(&i915->mm.free_work, __i915_gem_free_work);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index be14486f63a7..ae83737f1d48 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -200,6 +200,12 @@ i915_gem_object_has_struct_page(const struct drm_i915_gem_object *obj)
return i915_gem_object_type_has(obj, I915_GEM_OBJECT_HAS_STRUCT_PAGE);
}
+static inline bool
+i915_gem_object_has_iomem(const struct drm_i915_gem_object *obj)
+{
+ return i915_gem_object_type_has(obj, I915_GEM_OBJECT_HAS_IOMEM);
+}
+
static inline bool
i915_gem_object_is_shrinkable(const struct drm_i915_gem_object *obj)
{
@@ -540,4 +546,6 @@ i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj,
__i915_gem_object_invalidate_frontbuffer(obj, origin);
}
+int i915_gem_object_read_from_page(struct drm_i915_gem_object *obj, u64 offset, void *dst, int size);
+
#endif
--
2.25.1
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