[PATCH 3/4] iommu/io-pgtable: Add DART PTE support for t6000

[Sven Peter]

The DARTs present in the M1 Pro/Max SoC support a 42bit physical address
space by shifting the paddr and extending its mask inside the PTE.

Signed-off-by: Sven Peter <sven at svenpeter.dev>
---
 drivers/iommu/io-pgtable-arm.c | 30 +++++++++++++++++++++++++++++-
 include/linux/io-pgtable.h     |  2 ++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index a8c660b8b3e9..be66774aaf70 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -137,6 +137,11 @@
 #define APPLE_DART_PTE_SUBPAGE_START	GENMASK_ULL(63, 52)
 #define APPLE_DART_PTE_SUBPAGE_END	GENMASK_ULL(51, 40)
 
+#define APPLE_DART_PADDR_MASK_PS_36BIT	GENMASK_ULL(35, 12)
+#define APPLE_DART_PADDR_SHIFT_PS_36BIT	(0)
+#define APPLE_DART_PADDR_MASK_PS_42BIT	GENMASK_ULL(37, 10)
+#define APPLE_DART_PADDR_SHIFT_PS_42BIT	(4)
+
 /* IOPTE accessors */
 #define iopte_deref(pte,d) __va(iopte_to_paddr(pte, d))
 
@@ -171,6 +176,13 @@ static arm_lpae_iopte paddr_to_iopte(phys_addr_t paddr,
 {
 	arm_lpae_iopte pte = paddr;
 
+	if (data->iop.fmt == APPLE_DART) {
+		pte = paddr >> data->iop.cfg.apple_dart_cfg.paddr_shift;
+		pte &= data->iop.cfg.apple_dart_cfg.paddr_mask;
+
+		return pte;
+	}
+
 	/* Of the bits which overlap, either 51:48 or 15:12 are always RES0 */
 	return (pte | (pte >> (48 - 12))) & ARM_LPAE_PTE_ADDR_MASK;
 }
@@ -180,6 +192,12 @@ static phys_addr_t iopte_to_paddr(arm_lpae_iopte pte,
 {
 	u64 paddr = pte & ARM_LPAE_PTE_ADDR_MASK;
 
+	if (data->iop.fmt == APPLE_DART) {
+		paddr = pte & data->iop.cfg.apple_dart_cfg.paddr_mask;
+		paddr <<= data->iop.cfg.apple_dart_cfg.paddr_shift;
+		return paddr;
+	}
+
 	if (ARM_LPAE_GRANULE(data) < SZ_64K)
 		return paddr;
 
@@ -1122,8 +1140,18 @@ apple_dart_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
 	struct arm_lpae_io_pgtable *data;
 	int i;
 
-	if (cfg->oas > 36)
+	switch (cfg->oas) {
+	case 36:
+		cfg->apple_dart_cfg.paddr_shift = APPLE_DART_PADDR_SHIFT_PS_36BIT;
+		cfg->apple_dart_cfg.paddr_mask = APPLE_DART_PADDR_MASK_PS_36BIT;
+		break;
+	case 42:
+		cfg->apple_dart_cfg.paddr_shift = APPLE_DART_PADDR_SHIFT_PS_42BIT;
+		cfg->apple_dart_cfg.paddr_mask = APPLE_DART_PADDR_MASK_PS_42BIT;
+		break;
+	default:
 		return NULL;
+	}
 
 	data = arm_lpae_alloc_pgtable(cfg);
 	if (!data)
diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
index 86af6f0a00a2..4e26ebb0be93 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -136,6 +136,8 @@ struct io_pgtable_cfg {
 		struct {
 			u64 ttbr[4];
 			u32 n_ttbrs;
+			u32 paddr_shift;
+			u64 paddr_mask;
 		} apple_dart_cfg;
 	};
 };
-- 
2.25.1