In principle, Midgard GPUs supporting smaller VA sizes should only
require 3-level pagetables, since level 0 only resolves bits 48:40 of
the address. However, the kbase driver does not appear to have any
notion of a variable start level, and empirically T720 and T820 rapidly
blow up with translation faults unless given a full 4-level table,
despite only supporting a 33-bit VA size.

The 'real' IAS value is still valuable in terms of validating addresses
on map/unmap, so tweak the allocator to allow smaller values while still
forcing the resultant tables to the full 4 levels. As far as I can test,
this should make all known Midgard variants happy.

Fixes: d08d42de6432 ("iommu: io-pgtable: Add ARM Mali midgard MMU page table format")
Tested-by: Neil Armstrong <redacted>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/iommu/io-pgtable-arm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 90cb37af761c..ca51036aa53c 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c

@@ -1024,7 +1024,7 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
 	if (cfg->quirks)
 		return NULL;
 
-	if (cfg->ias != 48 || cfg->oas > 40)
+	if (cfg->ias > 48 || cfg->oas > 40)
 		return NULL;
 
 	cfg->pgsize_bitmap &= (SZ_4K | SZ_2M | SZ_1G);

@@ -1033,6 +1033,11 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
 	if (!data)
 		return NULL;
 
+	/* Mali seems to need a full 4-level table regardless of IAS */
+	if (data->levels < ARM_LPAE_MAX_LEVELS) {
+		data->levels = ARM_LPAE_MAX_LEVELS;
+		data->pgd_size = sizeof(arm_lpae_iopte);
+	}
 	/*
 	 * MEMATTR: Mali has no actual notion of a non-cacheable type, so the
 	 * best we can do is mimic the out-of-tree driver and hope that the

-- 
2.21.0.dirty


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