[PATCH v3 5/8] drm/i915/dg1: Reserve first 1MB of local memory

[Matthew Auld <matthew.auld@xxxxxxxxx>]

From: Imre Deak <imre.deak@xxxxxxxxx>

On DG1 A0/B0 steppings the first 1MB of local memory must be reserved.
One reason for this is that the 0xA0000-0xB0000 range is not accessible
by the display, probably since this region is redirected to another
memory location for legacy VGA compatibility.

BSpec: 50586
Testcase: igt/kms_big_fb/linear-64bpp-rotate-0

v2:
- Reserve the memory on B0 as well.

v3: replace DRM_DEBUG/DRM_ERROR with drm_dbg/drm_err

Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/intel_region_lmem.c | 56 +++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
index 71bb38706dbf..f5c12cbbaa86 100644
--- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c
+++ b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
@@ -143,6 +143,52 @@ intel_gt_setup_fake_lmem(struct intel_gt *gt)
 	return mem;
 }
 
+static bool get_legacy_lowmem_region(struct intel_uncore *uncore,
+				     u64 *start, u32 *size)
+{
+	*start = 0;
+	*size = 0;
+
+	if (!IS_DG1_REVID(uncore->i915, DG1_REVID_A0, DG1_REVID_B0))
+		return false;
+
+	*size = SZ_1M;
+
+	drm_dbg(&uncore->i915->drm, "LMEM: reserved legacy low-memory [0x%llx-0x%llx]\n",
+		*start, *start + *size);
+
+	return true;
+}
+
+static int reserve_lowmem_region(struct intel_uncore *uncore,
+				 struct intel_memory_region *mem)
+{
+	u64 reserve_start;
+	u64 reserve_end;
+	u64 region_start;
+	u32 region_size;
+	int ret;
+
+	if (!get_legacy_lowmem_region(uncore, &region_start, &region_size))
+		return 0;
+
+	reserve_start = region_start;
+	reserve_end = region_start + region_size;
+
+	if (!reserve_end)
+		return 0;
+
+	drm_dbg(&uncore->i915->drm, "LMEM: reserving low-memory region [0x%llx-0x%llx]\n",
+		reserve_start, reserve_end);
+	ret = intel_memory_region_reserve(mem,
+					  reserve_start,
+					  reserve_end - reserve_start);
+	if (ret)
+		drm_err(&uncore->i915->drm, "LMEM: reserving low memory region failed\n");
+
+	return ret;
+}
+
 static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
 {
 	struct drm_i915_private *i915 = gt->i915;
@@ -167,6 +213,16 @@ static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
 					 I915_GTT_PAGE_SIZE_4K,
 					 io_start,
 					 &intel_region_lmem_ops);
+	if (!IS_ERR(mem)) {
+		int err;
+
+		err = reserve_lowmem_region(uncore, mem);
+		if (err) {
+			intel_memory_region_put(mem);
+			return ERR_PTR(err);
+		}
+	}
+
 	if (!IS_ERR(mem)) {
 		drm_dbg(&i915->drm, "Local memory: %pR\n", &mem->region);
 		drm_dbg(&i915->drm, "Local memory IO start: %pa\n",
-- 
2.26.2

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