Message-Id: <20220621071848.14834-3-j@jannau.net>
Date:   Tue, 21 Jun 2022 09:18:45 +0200
From:   Janne Grunau <j@...nau.net>
To:     iommu@...ts.linux-foundation.org
Cc:     Konrad Dybcio <konrad.dybcio@...ainline.org>,
        asahi@...ts.linux.dev, Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Hector Martin <marcan@...can.st>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        Sven Peter <sven@...npeter.dev>, Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 2/5] iommu/io-pgtable: Move Apple DART support to its own file

The pte format used by the DARTs found in the Apple M1 (t8103) is not
fully compatible with io-pgtable-arm. The 24 MSB are used for subpage
protection (mapping only parts of page) and conflict with the address
mask. In addition bit 1 is not available for tagging entries but disables
subpage protection. Subpage protection could be useful to support a CPU
granule of 4k with the fixed IOMMU page size of 16k.

The DARTs found on Apple M1 Pro/Max/Ultra use another different pte
format which is even less compatible. To support an output address size
of 42 bit the address is shifted down by 4. Subpage protection is
mandatory and bit 1 signifies uncached mappings used by the display
controller.

It would be advantageous to share code for all known Apple DART
variants to support common features. The page table allocator for DARTs
is less complex since it uses a two levels of translation table without
support for huge pages.

Signed-off-by: Janne Grunau <j@...nau.net>

---

Changes in v3:
- move APPLE_DART to its own io-pgtable implementation, copied from
  io-pgtable-arm and simplified

Changes in v2:
- add APPLE_DART2 io-pgtable format

 MAINTAINERS                     |   1 +
 drivers/iommu/Kconfig           |   1 -
 drivers/iommu/Makefile          |   2 +-
 drivers/iommu/io-pgtable-arm.c  |  63 ----
 drivers/iommu/io-pgtable-dart.c | 580 ++++++++++++++++++++++++++++++++
 drivers/iommu/io-pgtable.c      |   2 +
 6 files changed, 584 insertions(+), 65 deletions(-)
 create mode 100644 drivers/iommu/io-pgtable-dart.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 1fc9ead83d2a..028b7e31e589 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1848,6 +1848,7 @@ F:	drivers/clk/clk-apple-nco.c
 F:	drivers/i2c/busses/i2c-pasemi-core.c
 F:	drivers/i2c/busses/i2c-pasemi-platform.c
 F:	drivers/iommu/apple-dart.c
+F:	drivers/iommu/io-pgtable-dart.c
 F:	drivers/irqchip/irq-apple-aic.c
 F:	drivers/mailbox/apple-mailbox.c
 F:	drivers/nvme/host/apple.c
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index c79a0df090c0..ed6d8260f330 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -294,7 +294,6 @@ config APPLE_DART
 	tristate "Apple DART IOMMU Support"
 	depends on ARCH_APPLE || (COMPILE_TEST && !GENERIC_ATOMIC64)
 	select IOMMU_API
-	select IOMMU_IO_PGTABLE_LPAE
 	default ARCH_APPLE
 	help
 	  Support for Apple DART (Device Address Resolution Table) IOMMUs
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 44475a9b3eea..bd68c93bbd62 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -29,4 +29,4 @@ obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
 obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
 obj-$(CONFIG_IOMMU_SVA) += iommu-sva-lib.o io-pgfault.o
 obj-$(CONFIG_SPRD_IOMMU) += sprd-iommu.o
-obj-$(CONFIG_APPLE_DART) += apple-dart.o
+obj-$(CONFIG_APPLE_DART) += apple-dart.o io-pgtable-dart.o
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 94ff319ae8ac..d7f5e23da643 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -130,9 +130,6 @@
 #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))
 
@@ -406,15 +403,6 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data,
 {
 	arm_lpae_iopte pte;
 
-	if (data->iop.fmt == 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;
@@ -1107,52 +1095,6 @@ 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;
-
-	/*
-	 * The table format itself always uses two levels, but the total VA
-	 * space is mapped by four separate tables, making the MMIO registers
-	 * an effective "level 1". For simplicity, though, we treat this
-	 * equivalently to LPAE stage 2 concatenation at level 2, with the
-	 * additional TTBRs each just pointing at consecutive pages.
-	 */
-	if (data->start_level < 1)
-		goto out_free_data;
-	if (data->start_level == 1 && data->pgd_bits > 2)
-		goto out_free_data;
-	if (data->start_level > 1)
-		data->pgd_bits = 0;
-	data->start_level = 2;
-	cfg->apple_dart_cfg.n_ttbrs = 1 << data->pgd_bits;
-	data->pgd_bits += data->bits_per_level;
-
-	data->pgd = __arm_lpae_alloc_pages(ARM_LPAE_PGD_SIZE(data), GFP_KERNEL,
-					   cfg);
-	if (!data->pgd)
-		goto out_free_data;
-
-	for (i = 0; i < cfg->apple_dart_cfg.n_ttbrs; ++i)
-		cfg->apple_dart_cfg.ttbr[i] =
-			virt_to_phys(data->pgd + i * ARM_LPAE_GRANULE(data));
-
-	return &data->iop;
-
-out_free_data:
-	kfree(data);
-	return NULL;
-}
-
 struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s1_init_fns = {
 	.alloc	= arm_64_lpae_alloc_pgtable_s1,
 	.free	= arm_lpae_free_pgtable,
@@ -1178,11 +1120,6 @@ struct io_pgtable_init_fns io_pgtable_arm_mali_lpae_init_fns = {
 	.free	= arm_lpae_free_pgtable,
 };
 
-struct io_pgtable_init_fns io_pgtable_apple_dart_init_fns = {
-	.alloc	= apple_dart_alloc_pgtable,
-	.free	= arm_lpae_free_pgtable,
-};
-
 #ifdef CONFIG_IOMMU_IO_PGTABLE_LPAE_SELFTEST
 
 static struct io_pgtable_cfg *cfg_cookie __initdata;
diff --git a/drivers/iommu/io-pgtable-dart.c b/drivers/iommu/io-pgtable-dart.c
new file mode 100644
index 000000000000..0c5222942c65
--- /dev/null
+++ b/drivers/iommu/io-pgtable-dart.c
@@ -0,0 +1,580 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Apple DART page table allocator.
+ *
+ * Copyright (C) 2022 The Asahi Linux Contributors
+ *
+ * Based on io-pgtable-arm.
+ *
+ * Copyright (C) 2014 ARM Limited
+ *
+ * Author: Will Deacon <will.deacon@....com>
+ */
+
+#define pr_fmt(fmt)	"dart io-pgtable: " fmt
+
+#include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/io-pgtable.h>
+#include <linux/kernel.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <asm/barrier.h>
+
+#define DART_MAX_ADDR_BITS		52
+#define DART_MAX_LEVELS		3
+
+/* Struct accessors */
+#define io_pgtable_to_data(x)						\
+	container_of((x), struct dart_io_pgtable, iop)
+
+#define io_pgtable_ops_to_data(x)					\
+	io_pgtable_to_data(io_pgtable_ops_to_pgtable(x))
+
+/*
+ * Calculate the right shift amount to get to the portion describing level l
+ * in a virtual address mapped by the pagetable in d.
+ */
+#define DART_LVL_SHIFT(l, d)						\
+	(((DART_MAX_LEVELS - (l)) * (d)->bits_per_level) +		\
+	ilog2(sizeof(dart_iopte)))
+
+#define DART_GRANULE(d)						\
+	(sizeof(dart_iopte) << (d)->bits_per_level)
+#define DART_PGD_SIZE(d)					\
+	(sizeof(dart_iopte) << (d)->pgd_bits)
+
+#define DART_PTES_PER_TABLE(d)					\
+	(DART_GRANULE(d) >> ilog2(sizeof(dart_iopte)))
+
+/*
+ * Calculate the index at level l used to map virtual address a using the
+ * pagetable in d.
+ */
+#define DART_PGD_IDX(l, d)						\
+	((l) == (d)->start_level ? (d)->pgd_bits - (d)->bits_per_level : 0)
+
+#define DART_LVL_IDX(a, l, d)						\
+	(((u64)(a) >> DART_LVL_SHIFT(l, d)) &				\
+	 ((1 << ((d)->bits_per_level + DART_PGD_IDX(l, d))) - 1))
+
+/* Calculate the block/page mapping size at level l for pagetable in d. */
+#define DART_BLOCK_SIZE(l, d)	(1ULL << DART_LVL_SHIFT(l, d))
+
+#define APPLE_DART1_PADDR_MASK	GENMASK_ULL(35, 12)
+
+/* Apple DART1 protection bits */
+#define APPLE_DART1_PTE_PROT_NO_READ	BIT(8)
+#define APPLE_DART1_PTE_PROT_NO_WRITE	BIT(7)
+#define APPLE_DART1_PTE_PROT_SP_DIS	BIT(1)
+
+/* marks PTE as valid */
+#define APPLE_DART_PTE_VALID		BIT(0)
+
+/* IOPTE accessors */
+#define iopte_deref(pte, d) __va(iopte_to_paddr(pte, d))
+
+struct dart_io_pgtable {
+	struct io_pgtable	iop;
+
+	int			pgd_bits;
+	int			start_level;
+	int			bits_per_level;
+
+	void			*pgd;
+};
+
+typedef u64 dart_iopte;
+
+static inline bool iopte_leaf(dart_iopte pte, int lvl,
+			      enum io_pgtable_fmt fmt)
+{
+	return (lvl == (DART_MAX_LEVELS - 1)) && (pte & APPLE_DART_PTE_VALID);
+}
+
+static dart_iopte paddr_to_iopte(phys_addr_t paddr,
+				     struct dart_io_pgtable *data)
+{
+	return paddr & APPLE_DART1_PADDR_MASK;
+}
+
+static phys_addr_t iopte_to_paddr(dart_iopte pte,
+				  struct dart_io_pgtable *data)
+{
+	return pte & APPLE_DART1_PADDR_MASK;
+}
+
+static void *__dart_alloc_pages(size_t size, gfp_t gfp,
+				    struct io_pgtable_cfg *cfg)
+{
+	struct device *dev = cfg->iommu_dev;
+	int order = get_order(size);
+	struct page *p;
+
+	VM_BUG_ON((gfp & __GFP_HIGHMEM));
+	p = alloc_pages_node(dev ? dev_to_node(dev) : NUMA_NO_NODE,
+			     gfp | __GFP_ZERO, order);
+	if (!p)
+		return NULL;
+
+	return page_address(p);
+}
+
+static void __dart_free_pages(void *pages, size_t size)
+{
+	free_pages((unsigned long)pages, get_order(size));
+}
+
+static void __dart_init_pte(struct dart_io_pgtable *data,
+				phys_addr_t paddr, dart_iopte prot,
+				int lvl, int num_entries, dart_iopte *ptep)
+{
+	dart_iopte pte = prot;
+	size_t sz = DART_BLOCK_SIZE(lvl, data);
+	int i;
+
+	if (lvl == DART_MAX_LEVELS - 1)
+		pte |= APPLE_DART1_PTE_PROT_SP_DIS;
+
+	pte |= APPLE_DART_PTE_VALID;
+
+	for (i = 0; i < num_entries; i++)
+		ptep[i] = pte | paddr_to_iopte(paddr + i * sz, data);
+}
+
+static int dart_init_pte(struct dart_io_pgtable *data,
+			     unsigned long iova, phys_addr_t paddr,
+			     dart_iopte prot, int lvl, int num_entries,
+			     dart_iopte *ptep)
+{
+	int i;
+
+	for (i = 0; i < num_entries; i++)
+		if (iopte_leaf(ptep[i], lvl, data->iop.fmt)) {
+			/* We require an unmap first */
+			WARN_ON(iopte_leaf(ptep[i], lvl, data->iop.fmt));
+			return -EEXIST;
+		}
+
+	__dart_init_pte(data, paddr, prot, lvl, num_entries, ptep);
+	return 0;
+}
+
+static dart_iopte dart_install_table(dart_iopte *table,
+					     dart_iopte *ptep,
+					     dart_iopte curr,
+					     struct dart_io_pgtable *data)
+{
+	dart_iopte old, new;
+
+	new = paddr_to_iopte(__pa(table), data) | APPLE_DART_PTE_VALID;
+
+	/*
+	 * Ensure the table itself is visible before its PTE can be.
+	 * Whilst we could get away with cmpxchg64_release below, this
+	 * doesn't have any ordering semantics when !CONFIG_SMP.
+	 */
+	dma_wmb();
+
+	old = cmpxchg64_relaxed(ptep, curr, new);
+
+	return old;
+}
+
+static int __dart_map(struct dart_io_pgtable *data, unsigned long iova,
+			  phys_addr_t paddr, size_t size, size_t pgcount,
+			  dart_iopte prot, int lvl, dart_iopte *ptep,
+			  gfp_t gfp, size_t *mapped)
+{
+	dart_iopte *cptep, pte;
+	size_t block_size = DART_BLOCK_SIZE(lvl, data);
+	size_t tblsz = DART_GRANULE(data);
+	struct io_pgtable_cfg *cfg = &data->iop.cfg;
+	int ret = 0, num_entries, max_entries, map_idx_start;
+
+	/* Find our entry at the current level */
+	map_idx_start = DART_LVL_IDX(iova, lvl, data);
+	ptep += map_idx_start;
+
+	/* If we can install a leaf entry at this level, then do so */
+	if (size == block_size) {
+		max_entries = DART_PTES_PER_TABLE(data) - map_idx_start;
+		num_entries = min_t(int, pgcount, max_entries);
+		ret = dart_init_pte(data, iova, paddr, prot, lvl, num_entries, ptep);
+		if (!ret && mapped)
+			*mapped += num_entries * size;
+
+		return ret;
+	}
+
+	/* We can't allocate tables at the final level */
+	if (WARN_ON(lvl >= DART_MAX_LEVELS - 1))
+		return -EINVAL;
+
+	/* Grab a pointer to the next level */
+	pte = READ_ONCE(*ptep);
+	if (!pte) {
+		cptep = __dart_alloc_pages(tblsz, gfp, cfg);
+		if (!cptep)
+			return -ENOMEM;
+
+		pte = dart_install_table(cptep, ptep, 0, data);
+		if (pte)
+			__dart_free_pages(cptep, tblsz);
+	}
+
+	if (pte && !iopte_leaf(pte, lvl, data->iop.fmt)) {
+		cptep = iopte_deref(pte, data);
+	} else if (pte) {
+		/* We require an unmap first */
+		WARN_ON(pte);
+		return -EEXIST;
+	}
+
+	/* Rinse, repeat */
+	return __dart_map(data, iova, paddr, size, pgcount, prot, lvl + 1,
+			      cptep, gfp, mapped);
+}
+
+static dart_iopte dart_prot_to_pte(struct dart_io_pgtable *data,
+					   int prot)
+{
+	dart_iopte pte = 0;
+
+	if (!(prot & IOMMU_WRITE))
+		pte |= APPLE_DART1_PTE_PROT_NO_WRITE;
+	if (!(prot & IOMMU_READ))
+		pte |= APPLE_DART1_PTE_PROT_NO_READ;
+
+	return pte;
+}
+
+static int dart_map_pages(struct io_pgtable_ops *ops, unsigned long iova,
+			      phys_addr_t paddr, size_t pgsize, size_t pgcount,
+			      int iommu_prot, gfp_t gfp, size_t *mapped)
+{
+	struct dart_io_pgtable *data = io_pgtable_ops_to_data(ops);
+	struct io_pgtable_cfg *cfg = &data->iop.cfg;
+	dart_iopte *ptep = data->pgd;
+	int ret, lvl = data->start_level;
+	dart_iopte prot;
+	long iaext = (s64)iova >> cfg->ias;
+
+	if (WARN_ON(!pgsize || (pgsize & cfg->pgsize_bitmap) != pgsize))
+		return -EINVAL;
+
+	if (WARN_ON(iaext || paddr >> cfg->oas))
+		return -ERANGE;
+
+	/* If no access, then nothing to do */
+	if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
+		return 0;
+
+	prot = dart_prot_to_pte(data, iommu_prot);
+	ret = __dart_map(data, iova, paddr, pgsize, pgcount, prot, lvl,
+			     ptep, gfp, mapped);
+	/*
+	 * Synchronise all PTE updates for the new mapping before there's
+	 * a chance for anything to kick off a table walk for the new iova.
+	 */
+	wmb();
+
+	return ret;
+}
+
+static int dart_map(struct io_pgtable_ops *ops, unsigned long iova,
+			phys_addr_t paddr, size_t size, int iommu_prot, gfp_t gfp)
+{
+	return dart_map_pages(ops, iova, paddr, size, 1, iommu_prot, gfp,
+				  NULL);
+}
+
+static void __dart_free_pgtable(struct dart_io_pgtable *data, int lvl,
+				    dart_iopte *ptep)
+{
+	dart_iopte *start, *end;
+	unsigned long table_size;
+
+	if (lvl == data->start_level)
+		table_size = DART_PGD_SIZE(data);
+	else
+		table_size = DART_GRANULE(data);
+
+	start = ptep;
+
+	/* Only leaf entries at the last level */
+	if (lvl == DART_MAX_LEVELS - 1)
+		end = ptep;
+	else
+		end = (void *)ptep + table_size;
+
+	while (ptep != end) {
+		dart_iopte pte = *ptep++;
+
+		if (!pte || iopte_leaf(pte, lvl, data->iop.fmt))
+			continue;
+
+		__dart_free_pgtable(data, lvl + 1, iopte_deref(pte, data));
+	}
+
+	__dart_free_pages(start, table_size);
+}
+
+static size_t __dart_unmap(struct dart_io_pgtable *data,
+			       struct iommu_iotlb_gather *gather,
+			       unsigned long iova, size_t size, size_t pgcount,
+			       int lvl, dart_iopte *ptep)
+{
+	dart_iopte pte;
+	struct io_pgtable *iop = &data->iop;
+	int i = 0, num_entries, max_entries, unmap_idx_start;
+
+	/* Something went horribly wrong and we ran out of page table */
+	if (WARN_ON(lvl == DART_MAX_LEVELS))
+		return 0;
+
+	unmap_idx_start = DART_LVL_IDX(iova, lvl, data);
+	ptep += unmap_idx_start;
+	pte = READ_ONCE(*ptep);
+	if (WARN_ON(!pte))
+		return 0;
+
+	/* If the size matches this level, we're in the right place */
+	if (size == DART_BLOCK_SIZE(lvl, data)) {
+		max_entries = DART_PTES_PER_TABLE(data) - unmap_idx_start;
+		num_entries = min_t(int, pgcount, max_entries);
+
+		while (i < num_entries) {
+			pte = READ_ONCE(*ptep);
+			if (WARN_ON(!pte))
+				break;
+
+			/* clear pte */
+			*ptep = 0;
+
+			if (!iopte_leaf(pte, lvl, iop->fmt)) {
+				/* Also flush any partial walks */
+				io_pgtable_tlb_flush_walk(iop, iova + i * size, size,
+							  DART_GRANULE(data));
+				__dart_free_pgtable(data, lvl + 1, iopte_deref(pte, data));
+			} else if (!iommu_iotlb_gather_queued(gather)) {
+				io_pgtable_tlb_add_page(iop, gather, iova + i * size, size);
+			}
+
+			ptep++;
+			i++;
+		}
+
+		return i * size;
+	}
+
+	/* Keep on walkin' */
+	ptep = iopte_deref(pte, data);
+	return __dart_unmap(data, gather, iova, size, pgcount, lvl + 1, ptep);
+}
+
+static size_t dart_unmap_pages(struct io_pgtable_ops *ops, unsigned long iova,
+				   size_t pgsize, size_t pgcount,
+				   struct iommu_iotlb_gather *gather)
+{
+	struct dart_io_pgtable *data = io_pgtable_ops_to_data(ops);
+	struct io_pgtable_cfg *cfg = &data->iop.cfg;
+	dart_iopte *ptep = data->pgd;
+	long iaext = (s64)iova >> cfg->ias;
+
+	if (WARN_ON(!pgsize || (pgsize & cfg->pgsize_bitmap) != pgsize || !pgcount))
+		return 0;
+
+	if (WARN_ON(iaext))
+		return 0;
+
+	return __dart_unmap(data, gather, iova, pgsize, pgcount,
+				data->start_level, ptep);
+}
+
+static size_t dart_unmap(struct io_pgtable_ops *ops, unsigned long iova,
+			     size_t size, struct iommu_iotlb_gather *gather)
+{
+	return dart_unmap_pages(ops, iova, size, 1, gather);
+}
+
+static phys_addr_t dart_iova_to_phys(struct io_pgtable_ops *ops,
+					 unsigned long iova)
+{
+	struct dart_io_pgtable *data = io_pgtable_ops_to_data(ops);
+	dart_iopte pte, *ptep = data->pgd;
+	int lvl = data->start_level;
+
+	do {
+		/* Valid IOPTE pointer? */
+		if (!ptep)
+			return 0;
+
+		/* Grab the IOPTE we're interested in */
+		ptep += DART_LVL_IDX(iova, lvl, data);
+		pte = READ_ONCE(*ptep);
+
+		/* Valid entry? */
+		if (!pte)
+			return 0;
+
+		/* Leaf entry? */
+		if (iopte_leaf(pte, lvl, data->iop.fmt))
+			goto found_translation;
+
+		/* Take it to the next level */
+		ptep = iopte_deref(pte, data);
+	} while (++lvl < DART_MAX_LEVELS);
+
+	/* Ran out of page tables to walk */
+	return 0;
+
+found_translation:
+	iova &= (DART_BLOCK_SIZE(lvl, data) - 1);
+	return iopte_to_paddr(pte, data) | iova;
+}
+
+static void dart_restrict_pgsizes(struct io_pgtable_cfg *cfg)
+{
+	unsigned long granule, page_sizes;
+	unsigned int max_addr_bits = 48;
+
+	/*
+	 * We need to restrict the supported page sizes to match the
+	 * translation regime for a particular granule. Aim to match
+	 * the CPU page size if possible, otherwise prefer smaller sizes.
+	 * While we're at it, restrict the block sizes to match the
+	 * chosen granule.
+	 */
+	if (cfg->pgsize_bitmap & PAGE_SIZE)
+		granule = PAGE_SIZE;
+	else if (cfg->pgsize_bitmap & ~PAGE_MASK)
+		granule = 1UL << __fls(cfg->pgsize_bitmap & ~PAGE_MASK);
+	else if (cfg->pgsize_bitmap & PAGE_MASK)
+		granule = 1UL << __ffs(cfg->pgsize_bitmap & PAGE_MASK);
+	else
+		granule = 0;
+
+	switch (granule) {
+	case SZ_4K:
+		page_sizes = (SZ_4K | SZ_2M | SZ_1G);
+		break;
+	case SZ_16K:
+		page_sizes = (SZ_16K | SZ_32M);
+		break;
+	default:
+		page_sizes = 0;
+	}
+
+	cfg->pgsize_bitmap &= page_sizes;
+	cfg->ias = min(cfg->ias, max_addr_bits);
+	cfg->oas = min(cfg->oas, max_addr_bits);
+}
+
+static struct dart_io_pgtable *
+dart_alloc_pgtable(struct io_pgtable_cfg *cfg)
+{
+	struct dart_io_pgtable *data;
+	int bits_per_level, levels, va_bits, pg_shift;
+
+	dart_restrict_pgsizes(cfg);
+
+	if (!(cfg->pgsize_bitmap & (SZ_4K | SZ_16K)))
+		return NULL;
+
+	if (cfg->ias > DART_MAX_ADDR_BITS)
+		return NULL;
+
+	if (cfg->oas > DART_MAX_ADDR_BITS)
+		return NULL;
+
+	pg_shift = __ffs(cfg->pgsize_bitmap);
+	bits_per_level = pg_shift - ilog2(sizeof(dart_iopte));
+
+	va_bits = cfg->ias - pg_shift;
+	levels = DIV_ROUND_UP(va_bits, bits_per_level);
+	if (levels > DART_MAX_LEVELS)
+		return NULL;
+
+	data = kmalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return NULL;
+
+	data->bits_per_level = bits_per_level;
+	data->start_level = DART_MAX_LEVELS - levels;
+
+	/* Calculate the actual size of our pgd (without concatenation) */
+	data->pgd_bits = va_bits - (data->bits_per_level * (levels - 1));
+
+	data->iop.ops = (struct io_pgtable_ops) {
+		.map		= dart_map,
+		.map_pages	= dart_map_pages,
+		.unmap		= dart_unmap,
+		.unmap_pages	= dart_unmap_pages,
+		.iova_to_phys	= dart_iova_to_phys,
+	};
+
+	return data;
+}
+
+static struct io_pgtable *
+apple_dart_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
+{
+	struct dart_io_pgtable *data;
+	int i;
+
+	if (!cfg->coherent_walk)
+		return NULL;
+
+	if (cfg->oas > 36)
+		return NULL;
+
+	data = dart_alloc_pgtable(cfg);
+	if (!data)
+		return NULL;
+
+	/*
+	 * The table format itself always uses two levels, but the total VA
+	 * space is mapped by four separate tables, making the MMIO registers
+	 * an effective "level 1". For simplicity, though, we treat this
+	 * equivalently to LPAE stage 2 concatenation at level 2, with the
+	 * additional TTBRs each just pointing at consecutive pages.
+	 */
+	if (data->start_level == 0 && data->pgd_bits > 2)
+		goto out_free_data;
+	if (data->start_level > 0)
+		data->pgd_bits = 0;
+	data->start_level = 1;
+	cfg->apple_dart_cfg.n_ttbrs = 1 << data->pgd_bits;
+	data->pgd_bits += data->bits_per_level;
+
+	data->pgd = __dart_alloc_pages(DART_PGD_SIZE(data), GFP_KERNEL,
+					   cfg);
+	if (!data->pgd)
+		goto out_free_data;
+
+	for (i = 0; i < cfg->apple_dart_cfg.n_ttbrs; ++i)
+		cfg->apple_dart_cfg.ttbr[i] =
+			virt_to_phys(data->pgd + i * DART_GRANULE(data));
+
+	return &data->iop;
+
+out_free_data:
+	kfree(data);
+	return NULL;
+}
+
+static void apple_dart_free_pgtable(struct io_pgtable *iop)
+{
+	struct dart_io_pgtable *data = io_pgtable_to_data(iop);
+
+	__dart_free_pgtable(data, data->start_level, data->pgd);
+	kfree(data);
+}
+
+struct io_pgtable_init_fns io_pgtable_apple_dart_init_fns = {
+	.alloc	= apple_dart_alloc_pgtable,
+	.free	= apple_dart_free_pgtable,
+};
diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c
index f4bfcef98297..e6edc6686859 100644
--- a/drivers/iommu/io-pgtable.c
+++ b/drivers/iommu/io-pgtable.c
@@ -20,6 +20,8 @@ io_pgtable_init_table[IO_PGTABLE_NUM_FMTS] = {
 	[ARM_64_LPAE_S1] = &io_pgtable_arm_64_lpae_s1_init_fns,
 	[ARM_64_LPAE_S2] = &io_pgtable_arm_64_lpae_s2_init_fns,
 	[ARM_MALI_LPAE] = &io_pgtable_arm_mali_lpae_init_fns,
+#endif
+#ifdef CONFIG_APPLE_DART
 	[APPLE_DART] = &io_pgtable_apple_dart_init_fns,
 #endif
 #ifdef CONFIG_IOMMU_IO_PGTABLE_ARMV7S
-- 
2.35.1

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