On Thu, Mar 05, 2020 at 02:29:08PM +0100, Nirmoy Das wrote:

Calculate GEM VRAM bo's offset within vram-helper without depending on
bo->offset.

Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/drm_gem_vram_helper.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
index 92a11bb42365..2749c2d25ac4 100644
--- a/drivers/gpu/drm/drm_gem_vram_helper.c
+++ b/drivers/gpu/drm/drm_gem_vram_helper.c
@@ -198,6 +198,13 @@ u64 drm_gem_vram_mmap_offset(struct drm_gem_vram_object *gbo)
 }
 EXPORT_SYMBOL(drm_gem_vram_mmap_offset);

+static s64 drm_gem_vram_pg_offset(struct drm_gem_vram_object *gbo)
+{
+	if (WARN_ON_ONCE(!gbo->bo.mem.mm_node))
+		return 0;

returns 0 on error.

I am not sure if we should call this an error. This patch series removes below offset calculation from ttm_bo.c.

-	if (bo->mem.mm_node)
-		bo->offset = (bo->mem.start << PAGE_SHIFT) +
-		    bdev->man[bo->mem.mem_type].gpu_offset;
-	else
-		bo->offset = 0;
-

Most of the driver sets "bo->mem.mm_node". Thomas suggested to use this "return 0" in case some driver depends on bo->offset = 0.

+	return gbo->bo.mem.start;
+}
+
 /**
  * drm_gem_vram_offset() - \
 	Returns a GEM VRAM object's offset in video memory
@@ -214,7 +221,7 @@ s64 drm_gem_vram_offset(struct drm_gem_vram_object *gbo)
 {
 	if (WARN_ON_ONCE(!gbo->pin_count))
 		return (s64)-ENODEV;

returns -errno on error.

-	return gbo->bo.offset;
+	return drm_gem_vram_pg_offset(gbo) << PAGE_SHIFT;

And given that one calls the other behavior on error should better be
consistent ...

cheers,
  Gerd

Regards,

Nirmoy