[PATCH 1/3] iommu: io-pgtable: add DART pagetable format

[Sven Peter <sven@svenpeter.dev>]

Apple's DART iommu uses a pagetable format that's very similar to the ones
already implemented by io-pgtable.c.
Add a new format variant to support the required differences.

Signed-off-by: Sven Peter <sven@svenpeter.dev>
---
 drivers/iommu/Kconfig          | 13 +++++++
 drivers/iommu/io-pgtable-arm.c | 70 ++++++++++++++++++++++++++++++++++
 drivers/iommu/io-pgtable.c     |  3 ++
 include/linux/io-pgtable.h     |  6 +++
 4 files changed, 92 insertions(+)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 192ef8f61310..3c95c8524abe 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -39,6 +39,19 @@ config IOMMU_IO_PGTABLE_LPAE
 	  sizes at both stage-1 and stage-2, as well as address spaces
 	  up to 48-bits in size.

+config IOMMU_IO_PGTABLE_APPLE_DART
+	bool "Apple DART Descriptor Format"
+	select IOMMU_IO_PGTABLE
+	select IOMMU_IO_PGTABLE_LPAE
+	depends on ARM64 || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	help
+	  Enable support for the Apple DART iommu pagetable format.
+	  This format is a variant of the ARMv7/v8 Long Descriptor
+	  Format specific to Apple's iommu found in their SoCs.
+
+	  Say Y here if you have a Apple SoC like the M1 which
+	  contains DART iommus.
+
 config IOMMU_IO_PGTABLE_LPAE_SELFTEST
 	bool "LPAE selftests"
 	depends on IOMMU_IO_PGTABLE_LPAE
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 87def58e79b5..18674469313d 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -127,6 +127,10 @@
 #define ARM_MALI_LPAE_MEMATTR_IMP_DEF	0x88ULL
 #define ARM_MALI_LPAE_MEMATTR_WRITE_ALLOC 0x8DULL

+/* APPLE_DART_PTE_PROT_NO_WRITE actually maps to ARM_LPAE_PTE_AP_RDONLY  */
+#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))

@@ -381,6 +385,17 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data,
 {
 	arm_lpae_iopte pte;

+#ifdef CONFIG_IOMMU_IO_PGTABLE_APPLE_DART
+	if (data->iop.fmt == ARM_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;
+	}
+#endif
+
 	if (data->iop.fmt == ARM_64_LPAE_S1 ||
 	    data->iop.fmt == ARM_32_LPAE_S1) {
 		pte = ARM_LPAE_PTE_nG;
@@ -1043,6 +1058,54 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
 	return NULL;
 }

+#ifdef CONFIG_IOMMU_IO_PGTABLE_APPLE_DART
+static struct io_pgtable *
+apple_dart_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
+{
+	struct arm_lpae_io_pgtable *data;
+
+	if (cfg->ias > 38)
+		return NULL;
+	if (cfg->oas > 36)
+		return NULL;
+
+	if (!cfg->coherent_walk)
+		return NULL;
+
+	cfg->pgsize_bitmap &= SZ_16K;
+	if (!cfg->pgsize_bitmap)
+		return NULL;
+
+	data = arm_lpae_alloc_pgtable(cfg);
+	if (!data)
+		return NULL;
+
+	/*
+	 * the hardware only supports this specific three level pagetable layout with
+	 * the first level being encoded into four hardware registers
+	 */
+	data->start_level = ARM_LPAE_MAX_LEVELS - 2;
+	data->pgd_bits = 13;
+	data->bits_per_level = 11;
+
+	data->pgd = __arm_lpae_alloc_pages(ARM_LPAE_PGD_SIZE(data), GFP_KERNEL,
+					   cfg);
+	if (!data->pgd)
+		goto out_free_data;
+
+	cfg->apple_dart_cfg.pgd[0] = virt_to_phys(data->pgd);
+	cfg->apple_dart_cfg.pgd[1] = virt_to_phys(data->pgd + 0x4000);
+	cfg->apple_dart_cfg.pgd[2] = virt_to_phys(data->pgd + 0x8000);
+	cfg->apple_dart_cfg.pgd[3] = virt_to_phys(data->pgd + 0xc000);
+
+	return &data->iop;
+
+out_free_data:
+	kfree(data);
+	return NULL;
+}
+#endif
+
 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,
@@ -1068,6 +1131,13 @@ struct io_pgtable_init_fns io_pgtable_arm_mali_lpae_init_fns = {
 	.free	= arm_lpae_free_pgtable,
 };

+#ifdef CONFIG_IOMMU_IO_PGTABLE_APPLE_DART
+struct io_pgtable_init_fns io_pgtable_apple_dart_init_fns = {
+	.alloc	= apple_dart_alloc_pgtable,
+	.free	= arm_lpae_free_pgtable,
+};
+#endif
+
 #ifdef CONFIG_IOMMU_IO_PGTABLE_LPAE_SELFTEST

 static struct io_pgtable_cfg *cfg_cookie __initdata;
diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c
index 6e9917ce980f..d86590b0673a 100644
--- a/drivers/iommu/io-pgtable.c
+++ b/drivers/iommu/io-pgtable.c
@@ -27,6 +27,9 @@ io_pgtable_init_table[IO_PGTABLE_NUM_FMTS] = {
 #ifdef CONFIG_AMD_IOMMU
 	[AMD_IOMMU_V1] = &io_pgtable_amd_iommu_v1_init_fns,
 #endif
+#ifdef CONFIG_IOMMU_IO_PGTABLE_APPLE_DART
+	[ARM_APPLE_DART] = &io_pgtable_apple_dart_init_fns,
+#endif
 };

 struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt,
diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
index a4c9ca2c31f1..19d9b631d319 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -16,6 +16,7 @@ enum io_pgtable_fmt {
 	ARM_V7S,
 	ARM_MALI_LPAE,
 	AMD_IOMMU_V1,
+	ARM_APPLE_DART,
 	IO_PGTABLE_NUM_FMTS,
 };

@@ -136,6 +137,10 @@ struct io_pgtable_cfg {
 			u64	transtab;
 			u64	memattr;
 		} arm_mali_lpae_cfg;
+
+		struct {
+			u64 pgd[4];
+		} apple_dart_cfg;
 	};
 };

@@ -250,5 +255,6 @@ extern struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s2_init_fns;
 extern struct io_pgtable_init_fns io_pgtable_arm_v7s_init_fns;
 extern struct io_pgtable_init_fns io_pgtable_arm_mali_lpae_init_fns;
 extern struct io_pgtable_init_fns io_pgtable_amd_iommu_v1_init_fns;
+extern struct io_pgtable_init_fns io_pgtable_apple_dart_init_fns;

 #endif /* __IO_PGTABLE_H */
--
2.25.1