iommu/io-pgtable-arm: Support non-coherent stage-2 page tables

Commit 9e6ea59f ("iommu/io-pgtable: Support non-coherent page tables")
added support for non-coherent page-table walks to the Arm IOMMU page-table
backends. Unfortunately, it left the stage-2 allocator unchanged, so let's
hook that up in the same way.

Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/io-pgtable-arm.c

@@ -910,10 +910,16 @@ arm_64_lpae_alloc_pgtable_s2(struct io_pgtable_cfg *cfg, void *cookie)
 	}
 
 	/* VTCR */
-	reg = ARM_64_LPAE_S2_TCR_RES1 |
-	     (ARM_LPAE_TCR_SH_IS << ARM_LPAE_TCR_SH0_SHIFT) |
+	reg = ARM_64_LPAE_S2_TCR_RES1;
+	if (cfg->coherent_walk) {
+		reg |= (ARM_LPAE_TCR_SH_IS << ARM_LPAE_TCR_SH0_SHIFT) |
 		       (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_IRGN0_SHIFT) |
 		       (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_ORGN0_SHIFT);
+	} else {
+		reg |= (ARM_LPAE_TCR_SH_OS << ARM_LPAE_TCR_SH0_SHIFT) |
+		       (ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_IRGN0_SHIFT) |
+		       (ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_ORGN0_SHIFT);
+	}
 
 	sl = data->start_level;