Re: [PATCH v3 3/3] iommu: dart: Add DART iommu driver

[Rouven Czerwinski]

Hi Sven,

just a small comment, see inline.

On Thu, 2021-06-03 at 10:50 +0200, Sven Peter wrote:
> Apple's new SoCs use iommus for almost all peripherals. These Device
> Address Resolution Tables must be setup before these peripherals can
> act as DMA masters.
> 
> Signed-off-by: Sven Peter <sven@xxxxxxxxxxxxx>
> ---
>  MAINTAINERS                      |   1 +
>  drivers/iommu/Kconfig            |  15 +
>  drivers/iommu/Makefile           |   1 +
>  drivers/iommu/apple-dart-iommu.c | 966 +++++++++++++++++++++++++++++++
>  4 files changed, 983 insertions(+)
>  create mode 100644 drivers/iommu/apple-dart-iommu.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 4373d63f9ccf..cb9200ad05fe 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1245,6 +1245,7 @@ M:	Sven Peter <sven@xxxxxxxxxxxxx>
>  L:	iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
>  S:	Maintained
>  F:	Documentation/devicetree/bindings/iommu/apple,dart.yaml
> +F:	drivers/iommu/apple-dart-iommu.c
>  
>  APPLE SMC DRIVER
>  M:	Henrik Rydberg <rydberg@xxxxxxxxxxx>
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index 1f111b399bca..87882c628b46 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -249,6 +249,21 @@ config SPAPR_TCE_IOMMU
>  	  Enables bits of IOMMU API required by VFIO. The iommu_ops
>  	  is not implemented as it is not necessary for VFIO.
>  
> +config IOMMU_APPLE_DART
> +	tristate "Apple DART IOMMU Support"
> +	depends on ARM64 || (COMPILE_TEST && !GENERIC_ATOMIC64)
> +	select IOMMU_API
> +	select IOMMU_IO_PGTABLE
> +	select IOMMU_IO_PGTABLE_LPAE
> +	default ARCH_APPLE
> +	help
> +	  Support for Apple DART (Device Address Resolution Table) IOMMUs
> +	  found in Apple ARM SoCs like the M1.
> +	  This IOMMU is required for most peripherals using DMA to access
> +	  the main memory.
> +
> +	  Say Y here if you are using an Apple SoC with a DART IOMMU.
> +
>  # ARM IOMMU support
>  config ARM_SMMU
>  	tristate "ARM Ltd. System MMU (SMMU) Support"
> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
> index c0fb0ba88143..8c813f0ebc54 100644
> --- a/drivers/iommu/Makefile
> +++ b/drivers/iommu/Makefile
> @@ -29,3 +29,4 @@ obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
>  obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
>  obj-$(CONFIG_IOMMU_SVA_LIB) += iommu-sva-lib.o io-pgfault.o
>  obj-$(CONFIG_SPRD_IOMMU) += sprd-iommu.o
> +obj-$(CONFIG_IOMMU_APPLE_DART) += apple-dart-iommu.o
> diff --git a/drivers/iommu/apple-dart-iommu.c b/drivers/iommu/apple-dart-iommu.c
> new file mode 100644
> index 000000000000..2777852498de
> --- /dev/null
> +++ b/drivers/iommu/apple-dart-iommu.c
> @@ -0,0 +1,966 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Apple DART (Device Address Resolution Table) IOMMU driver
> + *
> + * Copyright (C) 2021 The Asahi Linux Contributors
> + *
> + * Based on arm/arm-smmu/arm-ssmu.c and arm/arm-smmu-v3/arm-smmu-v3.c
> + *  Copyright (C) 2013 ARM Limited
> + *  Copyright (C) 2015 ARM Limited
> + * and on exynos-iommu.c
> + *  Copyright (c) 2011,2016 Samsung Electronics Co., Ltd.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/dma-iommu.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/err.h>
> +#include <linux/interrupt.h>
> +#include <linux/io-pgtable.h>
> +#include <linux/iopoll.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_iommu.h>
> +#include <linux/of_platform.h>
> +#include <linux/pci.h>
> +#include <linux/platform_device.h>
> +#include <linux/ratelimit.h>
> +#include <linux/slab.h>
> +#include <linux/pci.h>
> +
> +#define DART_MAX_STREAMS 16
> +#define DART_MAX_TTBR 4
> +
> +#define DART_STREAM_ALL 0xffff
> +
> +#define DART_PARAMS1 0x00
> +#define DART_PARAMS_PAGE_SHIFT GENMASK(27, 24)
> +
> +#define DART_PARAMS2 0x04
> +#define DART_PARAMS_BYPASS_SUPPORT BIT(0)
> +
> +#define DART_STREAM_COMMAND 0x20
> +#define DART_STREAM_COMMAND_BUSY BIT(2)
> +#define DART_STREAM_COMMAND_INVALIDATE BIT(20)
> +
> +#define DART_STREAM_SELECT 0x34
> +
> +#define DART_ERROR 0x40
> +#define DART_ERROR_STREAM GENMASK(27, 24)
> +#define DART_ERROR_CODE GENMASK(23, 0)
> +#define DART_ERROR_FLAG BIT(31)
> +#define DART_ERROR_READ_FAULT BIT(4)
> +#define DART_ERROR_WRITE_FAULT BIT(3)
> +#define DART_ERROR_NO_PTE BIT(2)
> +#define DART_ERROR_NO_PMD BIT(1)
> +#define DART_ERROR_NO_TTBR BIT(0)
> +
> +#define DART_CONFIG 0x60
> +#define DART_CONFIG_LOCK BIT(15)
> +
> +#define DART_STREAM_COMMAND_BUSY_TIMEOUT 100
> +
> +#define DART_STREAM_REMAP 0x80
> +
> +#define DART_ERROR_ADDR_HI 0x54
> +#define DART_ERROR_ADDR_LO 0x50
> +
> +#define DART_TCR(sid) (0x100 + 4 * (sid))
> +#define DART_TCR_TRANSLATE_ENABLE BIT(7)
> +#define DART_TCR_BYPASS0_ENABLE BIT(8)
> +#define DART_TCR_BYPASS1_ENABLE BIT(12)
> +
> +#define DART_TTBR(sid, idx) (0x200 + 16 * (sid) + 4 * (idx))
> +#define DART_TTBR_VALID BIT(31)
> +#define DART_TTBR_SHIFT 12
> +
> +/*
> + * Private structure associated with each DART device.
> + *
> + * @dev: device struct
> + * @regs: mapped MMIO region
> + * @irq: interrupt number, can be shared with other DARTs
> + * @clks: clocks associated with this DART
> + * @num_clks: number of @clks
> + * @lock: lock for @used_sids and hardware operations involving this dart
> + * @used_sids: bitmap of streams attached to a domain
> + * @pgsize: pagesize supported by this DART
> + * @supports_bypass: indicates if this DART supports bypass mode
> + * @force_bypass: force bypass mode due to pagesize mismatch?
> + * @iommu: iommu core device
> + */
> +struct apple_dart {
> +	struct device *dev;
> +
> +	void __iomem *regs;
> +
> +	int irq;
> +	struct clk_bulk_data *clks;
> +	int num_clks;
> +
> +	spinlock_t lock;
> +
> +	u32 used_sids;
> +	u32 pgsize;
> +
> +	u32 supports_bypass : 1;
> +	u32 force_bypass : 1;
> +	u64 force_bypass_offset;
> +	u64 force_bypass_len;
> +
> +	struct iommu_device iommu;
> +};
> +
> +/*
> + * This structure is used to identify a single stream attached to a domain.
> + * It's used as a list inside that domain to be able to attach multiple
> + * streams to a single domain. Since multiple devices can use a single stream
> + * it additionally keeps track of how many devices are represented by this
> + * stream. Once that number reaches zero it is detached from the IOMMU domain
> + * and all translations from this stream are disabled.
> + *
> + * @dart: DART instance to which this stream belongs
> + * @sid: stream id within the DART instance
> + * @num_devices: count of devices attached to this stream
> + * @stream_head: list head for the next stream
> + */
> +struct apple_dart_stream {
> +	struct apple_dart *dart;
> +	u32 sid;
> +
> +	u32 num_devices;
> +
> +	struct list_head stream_head;
> +};
> +
> +/*
> + * This structure is attached to each iommu domain handled by a DART.
> + * A single domain is used to represent a single virtual address spaces.
> + * It is always allocated together with a page table.
> + *
> + * Streams are the smallest units the DART hardware can differentiate.
> + * These are pointed to the page table of a domain whenever a device is
> + * attached to it. A single stream can only be assigned to a single domain.
> + *
> + * Devices are assigned to at least a single and sometimes multiple individual
> + * streams (using the iommus property in the device tree). Multiple devices
> + * can theoretically be represented by the same stream, though this is usually
> + * not the case.
> + *
> + * We only keep track of streams here and just count how many devices are
> + * represented by each stream. When the last device is removed the whole stream
> + * is removed from the domain.
> + *
> + * @dart: pointer to the DART instance
> + * @pgtbl_ops: pagetable ops allocated by io-pgtable
> + * @type: domain type IOMMU_DOMAIN_IDENTITY_{IDENTITY,DMA,UNMANAGED,BLOCKED}
> + * @streams: list of streams attached to this domain
> + * @lock: spinlock for operations involving the list of streams
> + * @domain: core iommu domain pointer
> + */
> +struct apple_dart_domain {
> +	struct apple_dart *dart;
> +	struct io_pgtable_ops *pgtbl_ops;
> +
> +	unsigned int type;
> +
> +	struct list_head streams;
> +
> +	spinlock_t lock;
> +
> +	struct iommu_domain domain;
> +};
> +
> +/*
> + * This structure is attached to devices with dev_iommu_priv_set() on of_xlate
> + * and contains a list of streams bound to this device as defined in the
> + * device tree. Multiple DART instances can be attached to a single device
> + * and each stream is identified by its stream id.
> + * It's usually reference by a pointer called *cfg.
> + *
> + * A dynamic array instead of a linked list is used here since in almost
> + * all cases a device will just be attached to a single stream and streams
> + * are never removed after they have been added.
> + *
> + * @num_streams: number of streams attached
> + * @streams: array of structs to identify attached streams and the device link
> + *           to the iommu
> + */
> +struct apple_dart_master_cfg {
> +	int num_streams;
> +	struct {
> +		struct apple_dart *dart;
> +		u32 sid;
> +
> +		struct device_link *link;
> +	} streams[];
> +};
> +
> +static struct platform_driver apple_dart_driver;
> +static const struct iommu_ops apple_dart_iommu_ops;
> +static const struct iommu_flush_ops apple_dart_tlb_ops;
> +
> +static struct apple_dart_domain *to_dart_domain(struct iommu_domain *dom)
> +{
> +	return container_of(dom, struct apple_dart_domain, domain);
> +}
> +
> +static void apple_dart_hw_enable_translation(struct apple_dart *dart, u16 sid)
> +{
> +	writel(DART_TCR_TRANSLATE_ENABLE, dart->regs + DART_TCR(sid));
> +}
> +
> +static void apple_dart_hw_disable_dma(struct apple_dart *dart, u16 sid)
> +{
> +	writel(0, dart->regs + DART_TCR(sid));
> +}
> +
> +static void apple_dart_hw_enable_bypass(struct apple_dart *dart, u16 sid)
> +{
> +	WARN_ON(!dart->supports_bypass);
> +	writel(DART_TCR_BYPASS0_ENABLE | DART_TCR_BYPASS1_ENABLE,
> +	       dart->regs + DART_TCR(sid));
> +}
> +
> +static void apple_dart_hw_set_ttbr(struct apple_dart *dart, u16 sid, u16 idx,
> +				   phys_addr_t paddr)
> +{
> +	writel(DART_TTBR_VALID | (paddr >> DART_TTBR_SHIFT),
> +	       dart->regs + DART_TTBR(sid, idx));
> +}
> +
> +static void apple_dart_hw_clear_ttbr(struct apple_dart *dart, u16 sid, u16 idx)
> +{
> +	writel(0, dart->regs + DART_TTBR(sid, idx));
> +}
> +
> +static void apple_dart_hw_clear_all_ttbrs(struct apple_dart *dart, u16 sid)
> +{
> +	int i;
> +
> +	for (i = 0; i < 4; ++i)
> +		apple_dart_hw_clear_ttbr(dart, sid, i);
> +}
> +
> +static int apple_dart_hw_stream_command(struct apple_dart *dart, u16 sid_bitmap,
> +					u32 command)
> +{
> +	unsigned long flags;
> +	int ret;
> +	u32 command_reg;
> +
> +	spin_lock_irqsave(&dart->lock, flags);
> +
> +	writel(sid_bitmap, dart->regs + DART_STREAM_SELECT);
> +	writel(command, dart->regs + DART_STREAM_COMMAND);
> +
> +	ret = readl_poll_timeout_atomic(
> +		dart->regs + DART_STREAM_COMMAND, command_reg,
> +		!(command_reg & DART_STREAM_COMMAND_BUSY), 1,
> +		DART_STREAM_COMMAND_BUSY_TIMEOUT);
> +
> +	spin_unlock_irqrestore(&dart->lock, flags);
> +
> +	if (ret) {
> +		dev_err(dart->dev,
> +			"busy bit did not clear after command %x for streams %x\n",
> +			command, sid_bitmap);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int apple_dart_hw_invalidate_tlb_global(struct apple_dart *dart)
> +{
> +	return apple_dart_hw_stream_command(dart, DART_STREAM_ALL,
> +					    DART_STREAM_COMMAND_INVALIDATE);
> +}
> +
> +static int apple_dart_hw_invalidate_tlb_stream(struct apple_dart *dart, u16 sid)
> +{
> +	return apple_dart_hw_stream_command(dart, 1 << sid,
> +					    DART_STREAM_COMMAND_INVALIDATE);
> +}
> +
> +static int apple_dart_hw_reset(struct apple_dart *dart)
> +{
> +	int sid;
> +	u32 config;
> +
> +	config = readl(dart->regs + DART_CONFIG);
> +	if (config & DART_CONFIG_LOCK) {
> +		dev_err(dart->dev, "DART is locked down until reboot: %08x\n",
> +			config);
> +		return -EINVAL;
> +	}
> +
> +	for (sid = 0; sid < DART_MAX_STREAMS; ++sid) {
> +		apple_dart_hw_disable_dma(dart, sid);
> +		apple_dart_hw_clear_all_ttbrs(dart, sid);
> +		apple_dart_hw_enable_translation(dart, sid);
> +	}
> +
> +	/* restore stream identity map */
> +	writel(0x03020100, dart->regs + DART_STREAM_REMAP);
> +	writel(0x07060504, dart->regs + DART_STREAM_REMAP + 4);
> +	writel(0x0b0a0908, dart->regs + DART_STREAM_REMAP + 8);
> +	writel(0x0f0e0d0c, dart->regs + DART_STREAM_REMAP + 12);
> +
> +	/* clear any pending errors before the interrupt is unmasked */
> +	writel(readl(dart->regs + DART_ERROR), dart->regs + DART_ERROR);
> +
> +	return apple_dart_hw_invalidate_tlb_global(dart);
> +}
> +
> +static void apple_dart_domain_flush_tlb(struct apple_dart_domain *domain)
> +{
> +	unsigned long flags;
> +	struct apple_dart_stream *stream;
> +	struct apple_dart *dart = domain->dart;
> +
> +	if (!dart)
> +		return;
> +
> +	spin_lock_irqsave(&domain->lock, flags);
> +	list_for_each_entry(stream, &domain->streams, stream_head) {
> +		apple_dart_hw_invalidate_tlb_stream(stream->dart, stream->sid);
> +	}
> +	spin_unlock_irqrestore(&domain->lock, flags);
> +}
> +
> +static void apple_dart_flush_iotlb_all(struct iommu_domain *domain)
> +{
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +
> +	apple_dart_domain_flush_tlb(dart_domain);
> +}
> +
> +static void apple_dart_iotlb_sync(struct iommu_domain *domain,
> +				  struct iommu_iotlb_gather *gather)
> +{
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +
> +	apple_dart_domain_flush_tlb(dart_domain);
> +}
> +
> +static void apple_dart_iotlb_sync_map(struct iommu_domain *domain,
> +				      unsigned long iova, size_t size)
> +{
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +
> +	apple_dart_domain_flush_tlb(dart_domain);
> +}
> +
> +static void apple_dart_tlb_flush_all(void *cookie)
> +{
> +	struct apple_dart_domain *domain = cookie;
> +
> +	apple_dart_domain_flush_tlb(domain);
> +}
> +
> +static void apple_dart_tlb_flush_walk(unsigned long iova, size_t size,
> +				      size_t granule, void *cookie)
> +{
> +	struct apple_dart_domain *domain = cookie;
> +
> +	apple_dart_domain_flush_tlb(domain);
> +}
> +
> +static const struct iommu_flush_ops apple_dart_tlb_ops = {
> +	.tlb_flush_all = apple_dart_tlb_flush_all,
> +	.tlb_flush_walk = apple_dart_tlb_flush_walk,
> +	.tlb_add_page = NULL,
> +};
> +
> +static phys_addr_t apple_dart_iova_to_phys(struct iommu_domain *domain,
> +					   dma_addr_t iova)
> +{
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +	struct io_pgtable_ops *ops = dart_domain->pgtbl_ops;
> +
> +	if (domain->type == IOMMU_DOMAIN_IDENTITY)
> +		return iova;
> +	if (!ops)
> +		return -ENODEV;
> +
> +	return ops->iova_to_phys(ops, iova);
> +}
> +
> +static int apple_dart_map(struct iommu_domain *domain, unsigned long iova,
> +			  phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
> +{
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +	struct io_pgtable_ops *ops = dart_domain->pgtbl_ops;
> +
> +	if (!ops)
> +		return -ENODEV;
> +	if (prot & IOMMU_MMIO)
> +		return -EINVAL;
> +	if (prot & IOMMU_NOEXEC)
> +		return -EINVAL;
> +
> +	return ops->map(ops, iova, paddr, size, prot, gfp);
> +}
> +
> +static size_t apple_dart_unmap(struct iommu_domain *domain, unsigned long iova,
> +			       size_t size, struct iommu_iotlb_gather *gather)
> +{
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +	struct io_pgtable_ops *ops = dart_domain->pgtbl_ops;
> +
> +	if (!ops)
> +		return 0;
> +
> +	return ops->unmap(ops, iova, size, gather);
> +}
> +
> +static int apple_dart_domain_needs_pgtbl_ops(struct apple_dart *dart,
> +					     struct iommu_domain *domain)
> +{
> +	if (domain->type == IOMMU_DOMAIN_DMA)
> +		return 1;
> +	if (domain->type == IOMMU_DOMAIN_UNMANAGED)
> +		return 1;
> +	if (!dart->supports_bypass && domain->type == IOMMU_DOMAIN_IDENTITY)
> +		return 1;
> +	return 0;
> +}
> +
> +/* must be called with held dart_domain->lock */

You can remove this comment, include lockdep.h and…

> +static int apple_dart_finalize_domain(struct iommu_domain *domain)
> +{
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +	struct apple_dart *dart = dart_domain->dart;
> +	struct io_pgtable_cfg pgtbl_cfg;
> +

	lockdep_assert_held(&dart_domain->lock);

A lockdep enabled kernel will warn if this function is called without
the lock held, otherwise this gets optimized out. Same for the similar
comments below.

> +	if (dart_domain->pgtbl_ops)
> +		return 0;
> +	if (!apple_dart_domain_needs_pgtbl_ops(dart, domain))
> +		return 0;
> +
> +	pgtbl_cfg = (struct io_pgtable_cfg){
> +		.pgsize_bitmap = dart->pgsize,
> +		.ias = 32,
> +		.oas = 36,
> +		.coherent_walk = 1,
> +		.tlb = &apple_dart_tlb_ops,
> +		.iommu_dev = dart->dev,
> +	};
> +
> +	dart_domain->pgtbl_ops =
> +		alloc_io_pgtable_ops(ARM_APPLE_DART, &pgtbl_cfg, domain);
> +	if (!dart_domain->pgtbl_ops)
> +		return -ENOMEM;
> +
> +	domain->pgsize_bitmap = pgtbl_cfg.pgsize_bitmap;
> +	domain->geometry.aperture_start = 0;
> +	domain->geometry.aperture_end = DMA_BIT_MASK(32);
> +	domain->geometry.force_aperture = true;
> +
> +	// HACK: create a static pagetable to fake bypass mode
> +	if (domain->type == IOMMU_DOMAIN_IDENTITY) {
> +		u64 addr;
> +
> +		for (addr = 0; addr < dart->force_bypass_len;
> +		     addr += dart->pgsize)
> +			dart_domain->pgtbl_ops->map(
> +				dart_domain->pgtbl_ops, addr,
> +				dart->force_bypass_offset + addr, dart->pgsize,
> +				IOMMU_READ | IOMMU_WRITE, GFP_ATOMIC);
> +	}
> +
> +	return 0;
> +}
> +
> +static void apple_dart_stream_setup_ttbrs(struct apple_dart_domain *domain,
> +					  struct apple_dart *dart, u32 sid)
> +{
> +	int i;
> +	struct io_pgtable_cfg *pgtbl_cfg =
> +		&io_pgtable_ops_to_pgtable(domain->pgtbl_ops)->cfg;
> +
> +	for (i = 0; i < pgtbl_cfg->apple_dart_cfg.n_ttbrs; ++i)
> +		apple_dart_hw_set_ttbr(dart, sid, i,
> +				       pgtbl_cfg->apple_dart_cfg.ttbr[i]);
> +	for (; i < DART_MAX_TTBR; ++i)
> +		apple_dart_hw_clear_ttbr(dart, sid, i);
> +}
> +
> +/* must be called with held domain->lock */
> +static int apple_dart_attach_stream(struct apple_dart_domain *domain,
> +				    struct apple_dart *dart, u32 sid)
> +{
> +	unsigned long flags;
> +	struct apple_dart_stream *stream;
> +	int ret;
> +
> +	if (WARN_ON(dart->force_bypass &&
> +		    domain->type != IOMMU_DOMAIN_IDENTITY))
> +		return -EINVAL;
> +
> +	/*
> +	 * we can't mix and match DARTs that support bypass mode with those who don't
> +	 * because the iova space in fake bypass mode generally has an offset
> +	 */
> +	if (WARN_ON(domain->type == IOMMU_DOMAIN_IDENTITY &&
> +		    (domain->dart->supports_bypass != dart->supports_bypass)))
> +		return -EINVAL;
> +
> +	list_for_each_entry(stream, &domain->streams, stream_head) {
> +		if (stream->dart == dart && stream->sid == sid) {
> +			stream->num_devices++;
> +			return 0;
> +		}
> +	}
> +
> +	spin_lock_irqsave(&dart->lock, flags);
> +
> +	if (WARN_ON(dart->used_sids & BIT(sid))) {
> +		ret = -EINVAL;
> +		goto error;
> +	}
> +
> +	stream = kzalloc(sizeof(*stream), GFP_ATOMIC);
> +	if (!stream) {
> +		ret = -ENOMEM;
> +		goto error;
> +	}
> +
> +	stream->dart = dart;
> +	stream->sid = sid;
> +	stream->num_devices = 1;
> +	list_add(&stream->stream_head, &domain->streams);
> +
> +	dart->used_sids |= BIT(sid);
> +	spin_unlock_irqrestore(&dart->lock, flags);
> +
> +	apple_dart_hw_clear_all_ttbrs(stream->dart, stream->sid);
> +
> +	switch (domain->type) {
> +	case IOMMU_DOMAIN_IDENTITY:
> +		if (stream->dart->supports_bypass) {
> +			apple_dart_hw_enable_bypass(stream->dart, stream->sid);
> +		} else {
> +			apple_dart_stream_setup_ttbrs(domain, stream->dart,
> +						      stream->sid);
> +			apple_dart_hw_enable_translation(stream->dart,
> +							 stream->sid);
> +			apple_dart_hw_invalidate_tlb_stream(stream->dart,
> +							    stream->sid);
> +		}
> +		break;
> +	case IOMMU_DOMAIN_BLOCKED:
> +		apple_dart_hw_disable_dma(stream->dart, stream->sid);
> +		break;
> +	case IOMMU_DOMAIN_UNMANAGED:
> +	case IOMMU_DOMAIN_DMA:
> +		apple_dart_stream_setup_ttbrs(domain, stream->dart,
> +					      stream->sid);
> +		apple_dart_hw_enable_translation(stream->dart, stream->sid);
> +		apple_dart_hw_invalidate_tlb_stream(stream->dart, stream->sid);
> +		break;
> +	}
> +
> +	return 0;
> +
> +error:
> +	spin_unlock_irqrestore(&dart->lock, flags);
> +	return ret;
> +}
> +
> +static void apple_dart_disable_stream(struct apple_dart *dart, u32 sid)
> +{
> +	unsigned long flags;
> +
> +	apple_dart_hw_disable_dma(dart, sid);
> +	apple_dart_hw_clear_all_ttbrs(dart, sid);
> +	apple_dart_hw_invalidate_tlb_stream(dart, sid);
> +
> +	spin_lock_irqsave(&dart->lock, flags);
> +	dart->used_sids &= ~BIT(sid);
> +	spin_unlock_irqrestore(&dart->lock, flags);
> +}
> +
> +/* must be called with held domain->lock */
> +static void apple_dart_detach_stream(struct apple_dart_domain *domain,
> +				     struct apple_dart *dart, u32 sid)
> +{
> +	struct apple_dart_stream *stream;
> +
> +	list_for_each_entry(stream, &domain->streams, stream_head) {
> +		if (stream->dart == dart && stream->sid == sid) {
> +			stream->num_devices--;
> +
> +			if (stream->num_devices == 0) {
> +				apple_dart_disable_stream(dart, sid);
> +				list_del(&stream->stream_head);
> +				kfree(stream);
> +			}
> +			return;
> +		}
> +	}
> +}
> +
> +static int apple_dart_attach_dev(struct iommu_domain *domain,
> +				 struct device *dev)
> +{
> +	int ret;
> +	int i, j;
> +	unsigned long flags;
> +	struct apple_dart_master_cfg *cfg = dev_iommu_priv_get(dev);
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +	struct apple_dart *dart = cfg->streams[0].dart;
> +
> +	spin_lock_irqsave(&dart_domain->lock, flags);
> +
> +	if (!dart_domain->dart)
> +		dart_domain->dart = dart;
> +
> +	if (WARN_ON(dart->force_bypass &&
> +		    dart_domain->type != IOMMU_DOMAIN_IDENTITY)) {
> +		dev_warn(
> +			dev,
> +			"IOMMU must be in bypass mode but trying to attach to translated domain.\n");
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	ret = apple_dart_finalize_domain(domain);
> +	if (ret)
> +		goto out;
> +
> +	for (i = 0; i < cfg->num_streams; ++i) {
> +		ret = apple_dart_attach_stream(
> +			dart_domain, cfg->streams[i].dart, cfg->streams[i].sid);
> +		if (ret) {
> +			/* try to undo what we did before returning */
> +			for (j = 0; j < i; ++j)
> +				apple_dart_detach_stream(dart_domain,
> +							 cfg->streams[j].dart,
> +							 cfg->streams[j].sid);
> +
> +			goto out;
> +		}
> +	}
> +
> +	ret = 0;
> +
> +out:
> +	spin_unlock_irqrestore(&dart_domain->lock, flags);
> +	return ret;
> +}
> +
> +static void apple_dart_detach_dev(struct iommu_domain *domain,
> +				  struct device *dev)
> +{
> +	int i;
> +	unsigned long flags;
> +	struct apple_dart_master_cfg *cfg = dev_iommu_priv_get(dev);
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +
> +	spin_lock_irqsave(&dart_domain->lock, flags);
> +
> +	for (i = 0; i < cfg->num_streams; ++i)
> +		apple_dart_detach_stream(dart_domain, cfg->streams[i].dart,
> +					 cfg->streams[i].sid);
> +
> +	spin_unlock_irqrestore(&dart_domain->lock, flags);
> +}
> +
> +static struct iommu_device *apple_dart_probe_device(struct device *dev)
> +{
> +	struct apple_dart_master_cfg *cfg = dev_iommu_priv_get(dev);
> +	int i;
> +
> +	if (!cfg)
> +		return ERR_PTR(-ENODEV);
> +
> +	for (i = 0; i < cfg->num_streams; ++i) {
> +		cfg->streams[i].link =
> +			device_link_add(dev, cfg->streams[i].dart->dev,
> +					DL_FLAG_PM_RUNTIME | DL_FLAG_STATELESS);
> +	}
> +
> +	return &cfg->streams[0].dart->iommu;
> +}
> +
> +static void apple_dart_release_device(struct device *dev)
> +{
> +	struct apple_dart_master_cfg *cfg = dev_iommu_priv_get(dev);
> +	int i;
> +
> +	if (!cfg)
> +		return;
> +
> +	for (i = 0; i < cfg->num_streams; ++i)
> +		device_link_del(cfg->streams[i].link);
> +
> +	dev_iommu_priv_set(dev, NULL);
> +	kfree(cfg);
> +}
> +
> +static struct iommu_domain *apple_dart_domain_alloc(unsigned int type)
> +{
> +	struct apple_dart_domain *dart_domain;
> +
> +	if (type != IOMMU_DOMAIN_DMA && type != IOMMU_DOMAIN_UNMANAGED &&
> +	    type != IOMMU_DOMAIN_IDENTITY && type != IOMMU_DOMAIN_BLOCKED)
> +		return NULL;
> +
> +	dart_domain = kzalloc(sizeof(*dart_domain), GFP_KERNEL);
> +	if (!dart_domain)
> +		return NULL;
> +
> +	INIT_LIST_HEAD(&dart_domain->streams);
> +	spin_lock_init(&dart_domain->lock);
> +	iommu_get_dma_cookie(&dart_domain->domain);
> +	dart_domain->type = type;
> +
> +	return &dart_domain->domain;
> +}
> +
> +static void apple_dart_domain_free(struct iommu_domain *domain)
> +{
> +	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
> +
> +	WARN_ON(!list_empty(&dart_domain->streams));
> +
> +	kfree(dart_domain);
> +}
> +
> +static int apple_dart_of_xlate(struct device *dev, struct of_phandle_args *args)
> +{
> +	struct platform_device *iommu_pdev = of_find_device_by_node(args->np);
> +	struct apple_dart_master_cfg *cfg = dev_iommu_priv_get(dev);
> +	unsigned int num_streams = cfg ? cfg->num_streams : 0;
> +	struct apple_dart_master_cfg *cfg_new;
> +	struct apple_dart *dart = platform_get_drvdata(iommu_pdev);
> +
> +	if (args->args_count != 1)
> +		return -EINVAL;
> +
> +	cfg_new = krealloc(cfg, struct_size(cfg, streams, num_streams + 1),
> +			   GFP_KERNEL);
> +	if (!cfg_new)
> +		return -ENOMEM;
> +
> +	cfg = cfg_new;
> +	dev_iommu_priv_set(dev, cfg);
> +
> +	cfg->num_streams = num_streams;
> +	cfg->streams[cfg->num_streams].dart = dart;
> +	cfg->streams[cfg->num_streams].sid = args->args[0];
> +	cfg->num_streams++;
> +
> +	return 0;
> +}
> +
> +static struct iommu_group *apple_dart_device_group(struct device *dev)
> +{
> +#ifdef CONFIG_PCI
> +	struct iommu_group *group;
> +
> +	if (dev_is_pci(dev))
> +		group = pci_device_group(dev);
> +	else
> +		group = generic_device_group(dev);
> +
> +	return group;
> +#else
> +	return generic_device_group(dev);
> +#endif
> +}
> +
> +static const struct iommu_ops apple_dart_iommu_ops = {
> +	.domain_alloc = apple_dart_domain_alloc,
> +	.domain_free = apple_dart_domain_free,
> +	.attach_dev = apple_dart_attach_dev,
> +	.detach_dev = apple_dart_detach_dev,
> +	.map = apple_dart_map,
> +	.unmap = apple_dart_unmap,
> +	.flush_iotlb_all = apple_dart_flush_iotlb_all,
> +	.iotlb_sync = apple_dart_iotlb_sync,
> +	.iotlb_sync_map = apple_dart_iotlb_sync_map,
> +	.iova_to_phys = apple_dart_iova_to_phys,
> +	.probe_device = apple_dart_probe_device,
> +	.release_device = apple_dart_release_device,
> +	.device_group = apple_dart_device_group,
> +	.of_xlate = apple_dart_of_xlate,
> +	.pgsize_bitmap = -1UL, /* Restricted during dart probe */
> +};
> +
> +static irqreturn_t apple_dart_irq(int irq, void *dev)
> +{
> +	struct apple_dart *dart = dev;
> +	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
> +				      DEFAULT_RATELIMIT_BURST);
> +	const char *fault_name = NULL;
> +	u32 error = readl(dart->regs + DART_ERROR);
> +	u32 error_code = FIELD_GET(DART_ERROR_CODE, error);
> +	u32 addr_lo = readl(dart->regs + DART_ERROR_ADDR_LO);
> +	u32 addr_hi = readl(dart->regs + DART_ERROR_ADDR_HI);
> +	u64 addr = addr_lo | (((u64)addr_hi) << 32);
> +	u8 stream_idx = FIELD_GET(DART_ERROR_STREAM, error);
> +
> +	if (!(error & DART_ERROR_FLAG))
> +		return IRQ_NONE;
> +
> +	if (error_code & DART_ERROR_READ_FAULT)
> +		fault_name = "READ FAULT";
> +	else if (error_code & DART_ERROR_WRITE_FAULT)
> +		fault_name = "WRITE FAULT";
> +	else if (error_code & DART_ERROR_NO_PTE)
> +		fault_name = "NO PTE FOR IOVA";
> +	else if (error_code & DART_ERROR_NO_PMD)
> +		fault_name = "NO PMD FOR IOVA";
> +	else if (error_code & DART_ERROR_NO_TTBR)
> +		fault_name = "NO TTBR FOR IOVA";
> +
> +	if (WARN_ON(fault_name == NULL))
> +		fault_name = "unknown";
> +
> +	if (__ratelimit(&rs)) {
> +		dev_err(dart->dev,
> +			"translation fault: status:0x%x stream:%d code:0x%x (%s) at 0x%llx",
> +			error, stream_idx, error_code, fault_name, addr);
> +	}
> +
> +	writel(error, dart->regs + DART_ERROR);
> +	return IRQ_HANDLED;
> +}
> +
> +static int apple_dart_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	u32 dart_params[2];
> +	struct resource *res;
> +	struct apple_dart *dart;
> +	struct device *dev = &pdev->dev;
> +
> +	dart = devm_kzalloc(dev, sizeof(*dart), GFP_KERNEL);
> +	if (!dart)
> +		return -ENOMEM;
> +
> +	dart->dev = dev;
> +	spin_lock_init(&dart->lock);
> +
> +	if (pdev->num_resources < 1)
> +		return -ENODEV;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (resource_size(res) < 0x4000) {
> +		dev_err(dev, "MMIO region too small (%pr)\n", res);
> +		return -EINVAL;
> +	}
> +
> +	dart->regs = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(dart->regs))
> +		return PTR_ERR(dart->regs);
> +
> +	ret = devm_clk_bulk_get_all(dev, &dart->clks);
> +	if (ret < 0)
> +		return ret;
> +	dart->num_clks = ret;
> +
> +	ret = clk_bulk_prepare_enable(dart->num_clks, dart->clks);
> +	if (ret)
> +		return ret;
> +
> +	ret = apple_dart_hw_reset(dart);
> +	if (ret)
> +		return ret;
> +
> +	dart_params[0] = readl(dart->regs + DART_PARAMS1);
> +	dart_params[1] = readl(dart->regs + DART_PARAMS2);
> +	dart->pgsize = 1 << FIELD_GET(DART_PARAMS_PAGE_SHIFT, dart_params[0]);
> +	dart->supports_bypass = dart_params[1] & DART_PARAMS_BYPASS_SUPPORT;
> +	dart->force_bypass = dart->pgsize > PAGE_SIZE;
> +
> +	// HACK: these shouldn't be hardcoded here but come from the device tree
> +	dart->force_bypass_offset = 0x0800000000;
> +	dart->force_bypass_len = 0x0100000000;
> +
> +	dart->irq = platform_get_irq(pdev, 0);
> +	if (dart->irq < 0)
> +		return -ENODEV;
> +
> +	ret = devm_request_irq(dart->dev, dart->irq, apple_dart_irq,
> +			       IRQF_SHARED, "apple-dart fault handler", dart);
> +	if (ret)
> +		return ret;
> +
> +	platform_set_drvdata(pdev, dart);
> +
> +	ret = iommu_device_sysfs_add(&dart->iommu, dev, NULL, "apple-dart.%s",
> +				     dev_name(&pdev->dev));
> +	if (ret)
> +		return ret;
> +
> +	ret = iommu_device_register(&dart->iommu, &apple_dart_iommu_ops, dev);
> +	if (ret)
> +		return ret;
> +
> +	if (dev->bus->iommu_ops != &apple_dart_iommu_ops) {
> +		ret = bus_set_iommu(dev->bus, &apple_dart_iommu_ops);
> +		if (ret)
> +			return ret;
> +	}
> +#ifdef CONFIG_PCI
> +	if (dev->bus->iommu_ops != pci_bus_type.iommu_ops) {
> +		ret = bus_set_iommu(&pci_bus_type, &apple_dart_iommu_ops);
> +		if (ret)
> +			return ret;
> +	}
> +#endif
> +
> +	dev_info(
> +		&pdev->dev,
> +		"DART [pagesize %x, bypass support: %d, bypass forced: %d] initialized\n",
> +		dart->pgsize, dart->supports_bypass, dart->force_bypass);
> +	return 0;
> +}
> +
> +static int apple_dart_remove(struct platform_device *pdev)
> +{
> +	struct apple_dart *dart = platform_get_drvdata(pdev);
> +
> +	devm_free_irq(dart->dev, dart->irq, dart);
> +
> +	iommu_device_unregister(&dart->iommu);
> +	iommu_device_sysfs_remove(&dart->iommu);
> +
> +	clk_bulk_disable(dart->num_clks, dart->clks);
> +	clk_bulk_unprepare(dart->num_clks, dart->clks);
> +
> +	return 0;
> +}
> +
> +static void apple_dart_shutdown(struct platform_device *pdev)
> +{
> +	apple_dart_remove(pdev);
> +}
> +
> +static const struct of_device_id apple_dart_of_match[] = {
> +	{ .compatible = "apple,t8103-dart", .data = NULL },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, apple_dart_of_match);
> +
> +static struct platform_driver apple_dart_driver = {
> +	.driver	= {
> +		.name			= "apple-dart",
> +		.of_match_table		= apple_dart_of_match,
> +	},
> +	.probe	= apple_dart_probe,
> +	.remove	= apple_dart_remove,
> +	.shutdown = apple_dart_shutdown,
> +};
> +module_platform_driver(apple_dart_driver);
> +
> +MODULE_DESCRIPTION("IOMMU API for Apple's DART");
> +MODULE_AUTHOR("Sven Peter <sven@xxxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");

Regards,
Rouven