Apple's DART iommu uses a pagetable format that shares some
similarities with the ones already implemented by io-pgtable.c.
Add a new format variant to support the required differences
so that we don't have to duplicate the pagetable handling code.

Signed-off-by: Sven Peter <redacted>
---
  drivers/iommu/io-pgtable-arm.c | 62 ++++++++++++++++++++++++++++++++++
  drivers/iommu/io-pgtable.c     |  1 +
  include/linux/io-pgtable.h     |  7 ++++
  3 files changed, 70 insertions(+)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 87def58e79b5..1dd5c45b4b5b 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c

@@ -127,6 +127,9 @@
  #define ARM_MALI_LPAE_MEMATTR_IMP_DEF  0x88ULL
  #define ARM_MALI_LPAE_MEMATTR_WRITE_ALLOC 0x8DULL

+#define APPLE_DART_PTE_PROT_NO_WRITE (1<<7)
+#define APPLE_DART_PTE_PROT_NO_READ (1<<8)
+
  /* IOPTE accessors */
  #define iopte_deref(pte,d) __va(iopte_to_paddr(pte, d))

@@ -381,6 +384,15 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data,
  {
         arm_lpae_iopte pte;

+       if (data->iop.fmt == ARM_APPLE_DART) {
+               pte = 0;
+               if (!(prot & IOMMU_WRITE))
+                       pte |= APPLE_DART_PTE_PROT_NO_WRITE;
+               if (!(prot & IOMMU_READ))
+                       pte |= APPLE_DART_PTE_PROT_NO_READ;
+               return pte;

+       }
+
         if (data->iop.fmt == ARM_64_LPAE_S1 ||
             data->iop.fmt == ARM_32_LPAE_S1) {
                 pte = ARM_LPAE_PTE_nG;

@@ -1043,6 +1055,51 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
         return NULL;
  }

+static struct io_pgtable *
+apple_dart_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
+{
+       struct arm_lpae_io_pgtable *data;
+       int i;
+
+       if (cfg->oas > 36)
+               return NULL;
+
+       data = arm_lpae_alloc_pgtable(cfg);
+       if (!data)
+               return NULL;
+
+       /*
+        * Apple's DART always requires three levels with the first level being
+        * stored in four MMIO registers. We always concatenate the first and
+        * second level so that we only have to setup the MMIO registers once.
+        * This results in an effective two level pagetable.
+        */
+       if (data->start_level < 1)
+               return NULL;
+       if (data->start_level == 1 && data->pgd_bits > 2)
+               return NULL;
+       if (data->start_level > 1)
+               data->pgd_bits = 0;
+       data->start_level = 2;
+       cfg->apple_dart_cfg.n_ttbrs = 1 << data->pgd_bits;