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 <20220901012519.7167-3-j@jannau.net>
Date:   Fri, 02 Sep 2022 18:00:16 +0200
From:   "Sven Peter" <sven@svenpeter.dev>
To:     "Janne Grunau" <j@jannau.net>, iommu@lists.linux.dev
Cc:     "Konrad Dybcio" <konrad.dybcio@somainline.org>,
        asahi@lists.linux.dev, "Robin Murphy" <robin.murphy@arm.com>,
        "Alyssa Rosenzweig" <alyssa@rosenzweig.io>,
        "Hector Martin" <marcan@marcan.st>,
        "Joerg Roedel" <joro@8bytes.org>, "Will Deacon" <will@kernel.org>,
        "Sven Peter" <iommu@lists.linux-foundation.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 2/5] iommu/io-pgtable: Move Apple DART support to its own file
Content-Type: text/plain
Precedence: bulk


On Thu, Sep 1, 2022, at 03:25, Janne Grunau wrote:
> 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@jannau.net>
> Acked-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Sven Peter <sven@svenpeter.dev>

>
> ---
>
> Changes in v4:
> - split dart and io-pgtable-dart build to allow building dart as module
> - add missing "SELECT IOMMU_IO_PGTABLE"
> - made map/unmap_pages/iova_to_phys inon-recursive
> - replace pgd concatenation with multiple table handling
> - simplified config and page size checks
> - collected Robin's Ack
>
> 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           |  13 +-
>  drivers/iommu/Makefile          |   1 +
>  drivers/iommu/io-pgtable-arm.c  |  63 -----
>  drivers/iommu/io-pgtable-dart.c | 428 ++++++++++++++++++++++++++++++++
>  drivers/iommu/io-pgtable.c      |   2 +
>  6 files changed, 444 insertions(+), 64 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..026921c1df53 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -67,6 +67,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
> 
>  	  If unsure, say N here.
> 
> +config IOMMU_IO_PGTABLE_DART
> +	bool "Apple DART Formats"
> +	select IOMMU_IO_PGTABLE
> +	depends on ARM64 || (COMPILE_TEST && !GENERIC_ATOMIC64)
> +	help
> +	  Enable support for the Apple DART pagetable formats. These include
> +	  the t8020 and t6000/t8110 DART formats used in Apple M1/M2 family
> +	  SoCs.
> +
> +	  If unsure, say N here.
> +
>  endmenu
> 
>  config IOMMU_DEBUGFS
> @@ -294,7 +305,7 @@ config APPLE_DART
>  	tristate "Apple DART IOMMU Support"
>  	depends on ARCH_APPLE || (COMPILE_TEST && !GENERIC_ATOMIC64)
>  	select IOMMU_API
> -	select IOMMU_IO_PGTABLE_LPAE
> +	select IOMMU_IO_PGTABLE_DART
>  	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..cc9f381013c3 100644
> --- a/drivers/iommu/Makefile
> +++ b/drivers/iommu/Makefile
> @@ -8,6 +8,7 @@ obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
>  obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
>  obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
>  obj-$(CONFIG_IOMMU_IO_PGTABLE_LPAE) += io-pgtable-arm.o
> +obj-$(CONFIG_IOMMU_IO_PGTABLE_DART) += io-pgtable-dart.o
>  obj-$(CONFIG_IOASID) += ioasid.o
>  obj-$(CONFIG_IOMMU_IOVA) += iova.o
>  obj-$(CONFIG_OF_IOMMU)	+= of_iommu.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..43ef375812e6
> --- /dev/null
> +++ b/drivers/iommu/io-pgtable-dart.c
> @@ -0,0 +1,428 @@
> +// 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@arm.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 DART1_MAX_ADDR_BITS	36
> +
> +#define DART_MAX_TABLES		4
> +#define DART_LEVELS		2
> +
> +/* 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))
> +
> +#define DART_GRANULE(d)						\
> +	(sizeof(dart_iopte) << (d)->bits_per_level)
> +#define DART_PTES_PER_TABLE(d)					\
> +	(DART_GRANULE(d) >> ilog2(sizeof(dart_iopte)))
> +
> +#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			tbl_bits;
> +	int			bits_per_level;
> +
> +	void			*pgd[DART_MAX_TABLES];
> +};
> +
> +typedef u64 dart_iopte;
> +
> +
> +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);

no need to change this but Apple Silicon doesn't have NUMA so that
you could just use alloc_pages here.

> +	if (!p)
> +		return NULL;
> +
> +	return page_address(p);
> +}
> +
> +static int dart_init_pte(struct dart_io_pgtable *data,
> +			     unsigned long iova, phys_addr_t paddr,
> +			     dart_iopte prot, int num_entries,
> +			     dart_iopte *ptep)
> +{
> +	int i;
> +	dart_iopte pte = prot;
> +	size_t sz = data->iop.cfg.pgsize_bitmap;
> +
> +	for (i = 0; i < num_entries; i++)
> +		if (ptep[i] & APPLE_DART_PTE_VALID) {
> +			/* We require an unmap first */
> +			WARN_ON(ptep[i] & APPLE_DART_PTE_VALID);
> +			return -EEXIST;
> +		}
> +
> +	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);
> +
> +	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_get_table(struct dart_io_pgtable *data, unsigned long 
> iova)
> +{
> +	return (iova >> (3 * data->bits_per_level + 
> ilog2(sizeof(dart_iopte)))) &
> +		((1 << data->tbl_bits) - 1);
> +}
> +
> +static int dart_get_l1_index(struct dart_io_pgtable *data, unsigned 
> long iova)
> +{
> +
> +	return (iova >> (2 * data->bits_per_level + 
> ilog2(sizeof(dart_iopte)))) &
> +		 ((1 << data->bits_per_level) - 1);
> +}
> +
> +static int dart_get_l2_index(struct dart_io_pgtable *data, unsigned 
> long iova)
> +{
> +
> +	return (iova >> (data->bits_per_level + ilog2(sizeof(dart_iopte)))) &
> +		 ((1 << data->bits_per_level) - 1);
> +}
> +
> +static  dart_iopte *dart_get_l2(struct dart_io_pgtable *data, unsigned 
> long iova)
> +{
> +	dart_iopte pte, *ptep;
> +	int tbl = dart_get_table(data, iova);
> +
> +	ptep = data->pgd[tbl];
> +	if (!ptep)
> +		return NULL;
> +
> +	ptep += dart_get_l1_index(data, iova);
> +	pte = READ_ONCE(*ptep);
> +
> +	/* Valid entry? */
> +	if (!pte)
> +		return 0;
> +
> +	/* Deref to get level 2 table */
> +	return iopte_deref(pte, data);
> +}
> +
> +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;
> +	size_t tblsz = DART_GRANULE(data);
> +	int ret = 0, tbl, num_entries, max_entries, map_idx_start;
> +	dart_iopte pte, *cptep, *ptep;
> +	dart_iopte prot;
> +
> +	if (WARN_ON(pgsize != cfg->pgsize_bitmap))
> +		return -EINVAL;
> +
> +	if (WARN_ON(paddr >> cfg->oas))
> +		return -ERANGE;
> +
> +	/* If no access, then nothing to do */
> +	if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
> +		return 0;
> +
> +	tbl = dart_get_table(data, iova);
> +
> +	ptep = data->pgd[tbl];
> +	ptep += dart_get_l1_index(data, iova);
> +	pte = READ_ONCE(*ptep);
> +
> +	/* no L2 table present */
> +	if (!pte) {
> +		cptep = __dart_alloc_pages(tblsz, gfp, cfg);
> +		if (!cptep)
> +			return -ENOMEM;
> +
> +		pte = dart_install_table(cptep, ptep, 0, data);
> +		if (pte)
> +			free_pages((unsigned long)cptep, get_order(tblsz));
> +
> +		/* L2 table is present (now) */
> +		pte = READ_ONCE(*ptep);
> +	}
> +
> +	ptep = iopte_deref(pte, data);
> +
> +	/* install a leaf entries into L2 table */
> +	prot = dart_prot_to_pte(data, iommu_prot);
> +	map_idx_start = dart_get_l2_index(data, iova);
> +	max_entries = DART_PTES_PER_TABLE(data) - map_idx_start;
> +	num_entries = min_t(int, pgcount, max_entries);
> +	ptep += map_idx_start;
> +	ret = dart_init_pte(data, iova, paddr, prot, num_entries, ptep);
> +	if (!ret && mapped)
> +		*mapped += num_entries * pgsize;
> +
> +	/*
> +	 * 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 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;
> +	int i = 0, num_entries, max_entries, unmap_idx_start;
> +	dart_iopte pte, *ptep;
> +
> +	if (WARN_ON(pgsize != cfg->pgsize_bitmap || !pgcount))
> +		return 0;
> +
> +	ptep = dart_get_l2(data, iova);
> +
> +	/* Valid L2 IOPTE pointer? */
> +	if (WARN_ON(!ptep))
> +		return 0;
> +
> +	unmap_idx_start = dart_get_l2_index(data, iova);
> +	ptep += unmap_idx_start;
> +
> +	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 (!iommu_iotlb_gather_queued(gather))
> +			io_pgtable_tlb_add_page(&data->iop, gather,
> +						iova + i * pgsize, pgsize);
> +
> +		ptep++;
> +		i++;
> +	}
> +
> +	return i * pgsize;
> +}
> +
> +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;
> +
> +	ptep = dart_get_l2(data, iova);
> +
> +	/* Valid L2 IOPTE pointer? */
> +	if (!ptep)
> +		return 0;
> +
> +	ptep += dart_get_l2_index(data, iova);
> +
> +	pte = READ_ONCE(*ptep);
> +	/* Found translation */
> +	if (pte) {
> +		iova &= (data->iop.cfg.pgsize_bitmap - 1);
> +		return iopte_to_paddr(pte, data) | iova;
> +	}
> +
> +	/* Ran out of page tables to walk */
> +	return 0;
> +}
> +
> +static struct dart_io_pgtable *
> +dart_alloc_pgtable(struct io_pgtable_cfg *cfg)
> +{
> +	struct dart_io_pgtable *data;
> +	int tbl_bits, bits_per_level, va_bits, pg_shift;
> +
> +	pg_shift = __ffs(cfg->pgsize_bitmap);
> +	bits_per_level = pg_shift - ilog2(sizeof(dart_iopte));
> +
> +	va_bits = cfg->ias - pg_shift;
> +
> +	tbl_bits = max_t(int, 0, va_bits - (bits_per_level * DART_LEVELS));
> +	if ((1 << tbl_bits) > DART_MAX_TABLES)
> +		return NULL;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return NULL;
> +
> +	data->tbl_bits = tbl_bits;
> +	data->bits_per_level = bits_per_level;
> +
> +	data->iop.ops = (struct io_pgtable_ops) {
> +		.map_pages	= dart_map_pages,
> +		.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 > DART1_MAX_ADDR_BITS)
> +		return NULL;
> +
> +	if (cfg->ias > cfg->oas)
> +		return NULL;
> +
> +	if (!(cfg->pgsize_bitmap == SZ_4K || cfg->pgsize_bitmap == SZ_16K))
> +		return NULL;
> +
> +	data = dart_alloc_pgtable(cfg);
> +	if (!data)
> +		return NULL;
> +
> +	cfg->apple_dart_cfg.n_ttbrs = 1 << data->tbl_bits;
> +
> +	for (i = 0; i < cfg->apple_dart_cfg.n_ttbrs; ++i) {
> +		data->pgd[i] = __dart_alloc_pages(DART_GRANULE(data), GFP_KERNEL,
> +					   cfg);
> +		if (!data->pgd[i])
> +			goto out_free_data;
> +		cfg->apple_dart_cfg.ttbr[i] = virt_to_phys(data->pgd[i]);
> +	}
> +
> +	return &data->iop;
> +
> +out_free_data:
> +	while (--i >= 0)
> +		free_pages((unsigned long)data->pgd[i],
> +			   get_order(DART_GRANULE(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_iopte *ptep, *end;
> +	int i;
> +
> +	for (i = 0; i < (1 << data->tbl_bits) && data->pgd[i]; ++i) {
> +		ptep = data->pgd[i];
> +		end = (void *)ptep + DART_GRANULE(data);
> +
> +		while (ptep != end) {
> +			dart_iopte pte = *ptep++;
> +
> +			if (pte) {
> +				unsigned long page =
> +					(unsigned long)iopte_deref(pte, data);
> +
> +				free_pages(page, get_order(DART_GRANULE(data)));
> +			}
> +		}
> +		free_pages((unsigned long)data->pgd[i],
> +			   get_order(DART_GRANULE(data)));
> +	}
> +
> +	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..16205ea9272c 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_IOMMU_IO_PGTABLE_DART
>  	[APPLE_DART] = &io_pgtable_apple_dart_init_fns,
>  #endif
>  #ifdef CONFIG_IOMMU_IO_PGTABLE_ARMV7S
> -- 
> 2.35.1