We need to add support for pread'ing an LMEM object.

Signed-off-by: Matthew Auld <matthew.a...@intel.com>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
Cc: Abdiel Janulgue <abdiel.janul...@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_region_lmem.c | 73 ++++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_region_lmem.c 
b/drivers/gpu/drm/i915/intel_region_lmem.c
index c8bee0c18c88..67dc50be2e6b 100644
--- a/drivers/gpu/drm/i915/intel_region_lmem.c
+++ b/drivers/gpu/drm/i915/intel_region_lmem.c
@@ -26,10 +26,83 @@
 #include "intel_memory_region.h"
 #include "intel_region_lmem.h"
 
+static int region_lmem_pread(struct drm_i915_gem_object *obj,
+                            const struct drm_i915_gem_pread *args)
+{
+       struct drm_i915_private *i915 = to_i915(obj->base.dev);
+       intel_wakeref_t wakeref;
+       char __user *user_data;
+       unsigned int offset;
+       unsigned long idx;
+       u64 remain;
+       int ret;
+
+       ret = i915_gem_object_wait(obj,
+                                  I915_WAIT_INTERRUPTIBLE,
+                                  MAX_SCHEDULE_TIMEOUT);
+       if (ret)
+               return ret;
+
+       ret = i915_gem_object_pin_pages(obj);
+       if (ret)
+               return ret;
+
+       ret = mutex_lock_interruptible(&i915->drm.struct_mutex);
+       if (ret)
+               goto out_unpin;
+
+       wakeref = intel_runtime_pm_get(i915);
+
+       ret = i915_gem_object_set_to_wc_domain(obj, false);
+       mutex_unlock(&i915->drm.struct_mutex);
+       if (ret)
+               goto out_put;
+
+       remain = args->size;
+       user_data = u64_to_user_ptr(args->data_ptr);
+       offset = offset_in_page(args->offset);
+       for (idx = args->offset >> PAGE_SHIFT; remain; idx++) {
+               unsigned long unwritten;
+               void __iomem *vaddr;
+               int length;
+
+               length = remain;
+               if (offset + length > PAGE_SIZE)
+                       length = PAGE_SIZE - offset;
+
+               vaddr = i915_gem_object_lmem_io_map_page(obj, idx);
+               if (!vaddr) {
+                       ret = -ENOMEM;
+                       goto out_put;
+               }
+
+               unwritten = copy_to_user(user_data,
+                                        (void __force *)vaddr + offset,
+                                        length);
+               io_mapping_unmap_atomic(vaddr);
+               if (unwritten) {
+                       ret = -EFAULT;
+                       goto out_put;
+               }
+
+               remain -= length;
+               user_data += length;
+               offset = 0;
+       }
+
+out_put:
+       intel_runtime_pm_put(i915, wakeref);
+out_unpin:
+       i915_gem_object_unpin_pages(obj);
+
+       return ret;
+}
+
 static const struct drm_i915_gem_object_ops region_lmem_obj_ops = {
        .get_pages = i915_memory_region_get_pages_buddy,
        .put_pages = i915_memory_region_put_pages_buddy,
        .release = i915_gem_object_release_memory_region,
+       .pread = region_lmem_pread,
 };
 
 static struct drm_i915_gem_object *
-- 
2.20.1

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