[PATCH v2 1/3] iommu/io-pgtable-arm: Support coherency for Mali LPAE

[Robin Murphy]

Midgard GPUs have ACE-Lite master interfaces which allows systems to
integrate them in an I/O-coherent manner. It seems that from the GPU's
viewpoint, the rest of the system is its outer shareable domain, and so
even when snoop signals are wired up, they are only emitted for outer
shareable accesses. As such, setting the TTBR_SHARE_OUTER bit does
indeed get coherent pagetable walks working nicely for the coherent
T620 in the Arm Juno SoC.

Reviewed-by: Steven Price <steven.price at arm.com>
Tested-by: Neil Armstrong <narmstrong at baylibre.com>
Signed-off-by: Robin Murphy <robin.murphy at arm.com>
---
 drivers/iommu/io-pgtable-arm.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index dc7bcf858b6d..b4072a18e45d 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -440,7 +440,13 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data,
 				<< ARM_LPAE_PTE_ATTRINDX_SHIFT);
 	}
 
-	if (prot & IOMMU_CACHE)
+	/*
+	 * Also Mali has its own notions of shareability wherein its Inner
+	 * domain covers the cores within the GPU, and its Outer domain is
+	 * "outside the GPU" (i.e. either the Inner or System domain in CPU
+	 * terms, depending on coherency).
+	 */
+	if (prot & IOMMU_CACHE && data->iop.fmt != ARM_MALI_LPAE)
 		pte |= ARM_LPAE_PTE_SH_IS;
 	else
 		pte |= ARM_LPAE_PTE_SH_OS;
@@ -1049,6 +1055,9 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
 	cfg->arm_mali_lpae_cfg.transtab = virt_to_phys(data->pgd) |
 					  ARM_MALI_LPAE_TTBR_READ_INNER |
 					  ARM_MALI_LPAE_TTBR_ADRMODE_TABLE;
+	if (cfg->coherent_walk)
+		cfg->arm_mali_lpae_cfg.transtab |= ARM_MALI_LPAE_TTBR_SHARE_OUTER;
+
 	return &data->iop;
 
 out_free_data:
-- 
2.28.0.dirty