iommu/ipmmu-vmsa: Set the PTE contiguous hint bit when possible

The contiguous hint bit signals to the IOMMU that a range of 16 PTEs
refer to physically contiguous memory. It improves performances by
dividing the number of TLB lookups by 16, effectively implementing 64kB
page sizes.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 40 insertions, 3 deletions

diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
index f8f5b194a360..e64c616208e2 100644
--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c
@@ -209,6 +209,9 @@ static LIST_HEAD(ipmmu_devices);
 #define ARM_VMSA_PTE_MEMATTR_NC         (((pteval_t)0x5) << 2)
 #define ARM_VMSA_PTE_MEMATTR_DEV        (((pteval_t)0x1) << 2)
 
+#define ARM_VMSA_PTE_CONT_ENTRIES       16
+#define ARM_VMSA_PTE_CONT_SIZE          (PAGE_SIZE * ARM_VMSA_PTE_CONT_ENTRIES)
+
 #define IPMMU_PTRS_PER_PTE              512
 #define IPMMU_PTRS_PER_PMD              512
 #define IPMMU_PTRS_PER_PGD              4
@@ -569,10 +572,44 @@ static int ipmmu_alloc_init_pte(struct ipmmu_vmsa_device *mmu, pmd_t *pmd,
         pteval |= ARM_VMSA_PTE_SH_IS;
         start = pte;
 
-        /* Install the page table entries. */
+        /*
+         * Install the page table entries.
+         *
+         * Set the contiguous hint in the PTEs where possible. The hint
+         * indicates a series of ARM_VMSA_PTE_CONT_ENTRIES PTEs mapping a
+         * physically contiguous region with the following constraints:
+         *
+         * - The region start is aligned to ARM_VMSA_PTE_CONT_SIZE
+         * - Each PTE in the region has the contiguous hint bit set
+         *
+         * We don't support partial unmapping so there's no need to care about
+         * clearing the contiguous hint from neighbour PTEs.
+         */
         do {
-                *pte++ = pfn_pte(pfn++, __pgprot(pteval));
-                addr += PAGE_SIZE;
+                unsigned long chunk_end;
+
+                /*
+                 * If the address is aligned to a contiguous region size and the
+                 * mapping size is large enough, process the largest possible
+                 * number of PTEs multiple of ARM_VMSA_PTE_CONT_ENTRIES.
+                 * Otherwise process the smallest number of PTEs to align the
+                 * address to a contiguous region size or to complete the
+                 * mapping.
+                 */
+                if (IS_ALIGNED(addr, ARM_VMSA_PTE_CONT_SIZE) &&
+                    end - addr >= ARM_VMSA_PTE_CONT_SIZE) {
+                        chunk_end = round_down(end, ARM_VMSA_PTE_CONT_SIZE);
+                        pteval |= ARM_VMSA_PTE_CONT;
+                } else {
+                        chunk_end = min(ALIGN(addr, ARM_VMSA_PTE_CONT_SIZE),
+                                        end);
+                        pteval &= ~ARM_VMSA_PTE_CONT;
+                }
+
+                do {
+                        *pte++ = pfn_pte(pfn++, __pgprot(pteval));
+                        addr += PAGE_SIZE;
+                } while (addr != chunk_end);
         } while (addr != end);
 
         ipmmu_flush_pgtable(mmu, start, sizeof(*pte) * (pte - start));