[PATCH v3 31/37] drm/i915/lmem: add helper to get CPU accessible offset

[Matthew Auld <matthew.auld@intel.com>]

From: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>

LMEM can be accessed by the CPU through a BAR. The mapping itself should
be 1:1.

Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_lmem.c | 16 ++++++++++++++++
 drivers/gpu/drm/i915/gem/i915_gem_lmem.h |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_lmem.c b/drivers/gpu/drm/i915/gem/i915_gem_lmem.c
index f00078ac331e..8d0251af5dfc 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_lmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_lmem.c
@@ -225,6 +225,22 @@ void __iomem *i915_gem_object_lmem_io_map(struct drm_i915_gem_object *obj,
 	return io_mapping_map_wc(&obj->mm.region->iomap, offset, size);
 }
 
+resource_size_t i915_gem_object_lmem_io_offset(struct drm_i915_gem_object *obj,
+					       unsigned long n)
+{
+	struct intel_memory_region *mem = obj->mm.region;
+	dma_addr_t daddr;
+
+	/*
+	 * XXX: It's not a dma address, more a device address or physical
+	 * offset, so we are clearly abusing the semantics of the sg_table
+	 * here, and elsewhere like in the gtt paths.
+	 */
+	daddr = i915_gem_object_get_dma_address(obj, n);
+
+	return mem->io_start + daddr;
+}
+
 bool i915_gem_object_is_lmem(struct drm_i915_gem_object *obj)
 {
 	struct intel_memory_region *region = obj->mm.region;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_lmem.h b/drivers/gpu/drm/i915/gem/i915_gem_lmem.h
index 31a6462bdbb6..43e6e715eeed 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_lmem.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_lmem.h
@@ -21,6 +21,9 @@ void __iomem *
 i915_gem_object_lmem_io_map_page_atomic(struct drm_i915_gem_object *obj,
 					unsigned long n);
 
+resource_size_t i915_gem_object_lmem_io_offset(struct drm_i915_gem_object *obj,
+					       unsigned long n);
+
 bool i915_gem_object_is_lmem(struct drm_i915_gem_object *obj);
 
 struct drm_i915_gem_object *
-- 
2.20.1

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