[Intel-gfx] [PATCH 7/8] drm/i915: fixup the initial fb base on DG1

[Matthew Auld]

The offset we get looks to be the exact start of DSM, but the
inital_plane_vma expects the address to be relative.

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
---
 .../drm/i915/display/intel_plane_initial.c    | 22 +++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_plane_initial.c b/drivers/gpu/drm/i915/display/intel_plane_initial.c
index f797fcef18fc..b39d3a8dfe45 100644
--- a/drivers/gpu/drm/i915/display/intel_plane_initial.c
+++ b/drivers/gpu/drm/i915/display/intel_plane_initial.c
@@ -56,10 +56,24 @@ initial_plane_vma(struct drm_i915_private *i915,
 	if (!mem || plane_config->size == 0)
 		return NULL;
 
-	base = round_down(plane_config->base,
-			  I915_GTT_MIN_ALIGNMENT);
-	size = round_up(plane_config->base + plane_config->size,
-			mem->min_page_size);
+	base = plane_config->base;
+	if (IS_DGFX(i915)) {
+		/*
+		 * On discrete the base address should be somewhere in LMEM, but
+		 * depending on the size of LMEM the base address might
+		 * intersect with the start of DSM, like on DG1, in which case
+		 * we need the relative address. In such cases we might also
+		 * need to choose between inital fb vs fbc, if space is limited.
+		 *
+		 * On future discrete HW, like DG2, we should be able to just
+		 * allocate directly from LMEM, due to larger LMEM size.
+		 */
+		if (base >= i915->dsm.start)
+			base -= i915->dsm.start;
+	}
+
+	size = roundup(base + plane_config->size, mem->min_page_size);
+	base = round_down(base, I915_GTT_MIN_ALIGNMENT);
 	size -= base;
 
 	/*
-- 
2.34.1