[PATCH 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU

[PATCH 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU

[Vladimir Murzin]

Hi,

It seem that addition of cache support for M-class CPUs uncovered
latent bug in DMA usage. NOMMU memory model has been treated as being
always consistent; however, for R/M CPU classes memory can be covered
by MPU which in turn might configure RAM as Normal i.e. bufferable and
cacheable. It breaks dma_alloc_coherent() and friends, since data can
stuck in caches now or be buffered.

This patch set is trying to address the issue by providing region of
memory suitable for consistent DMA operations. It is supposed that
such region is marked by MPU as non-cacheable. Robin suggested to
advertise such memory as reserved shared-dma-pool, rather then using
homebrew command line option, and extend dma-coherent to provide
default DMA area in the similar way as it is done for CMA (PATCH
4/7). It allows us to offload all bookkeeping on generic coherent DMA
framework, and it seems that it might be reused by other architectures
like c6x and blackfin.

While reviewing/testing previous vesrions of the patch set it turned
out that dma-coherent does not take into account "dma-ranges" device
tree property, so it is addressed in PATCH 3/7.

For ARM, dedicated DMA region is required for cases other than:
 - MMU/MPU is off
 - cpu is v7m w/o cache support
 - device is coherent

In case one of the above conditions is true dma operations are forced
to be coherent and wired with dma_noop_ops.

To make life easier NOMMU dma operations are kept in separate
compilation unit.

Since the issue was reported in the same time as Benjamin sent his
patch [1] to allow mmap for NOMMU, his case is also addressed in this
series (PATCH 1/7 and PATCH 2/7).

Thanks!

[1] http://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8633/1

Changelog:
	RFC v6 -> v1
	       - dropped RFC tag
	       - added Alexandre's Tested-by

Vladimir Murzin (7):
  dma: Take into account dma_pfn_offset
  dma: Add simple dma_noop_mmap
  drivers: dma-coherent: Account dma_pfn_offset when used with device
    tree
  drivers: dma-coherent: Introduce default DMA pool
  ARM: NOMMU: Introduce dma operations for noMMU
  ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus
  ARM: dma-mapping: Remove traces of NOMMU code

 .../bindings/reserved-memory/reserved-memory.txt   |   3 +
 arch/arm/include/asm/dma-mapping.h                 |   3 +-
 arch/arm/mm/Kconfig                                |   2 +-
 arch/arm/mm/Makefile                               |   5 +-
 arch/arm/mm/dma-mapping-nommu.c                    | 253 +++++++++++++++++++++
 arch/arm/mm/dma-mapping.c                          |  26 +--
 drivers/base/dma-coherent.c                        |  76 ++++++-
 lib/dma-noop.c                                     |  29 ++-
 8 files changed, 356 insertions(+), 41 deletions(-)
 create mode 100644 arch/arm/mm/dma-mapping-nommu.c

-- 
2.0.0

[PATCH 1/7] dma: Take into account dma_pfn_offset

[Vladimir Murzin]

Even though dma-noop-ops assumes 1:1 memory mapping DMA memory range
can be different to RAM. For example, ARM STM32F4 MCU offers the
possibility to remap SDRAM from 0xc000_0000 to 0x0 to get CPU
performance boost, but DMA continue to see SDRAM at 0xc000_0000. This
difference in mapping is handled via device-tree "dma-range" property
which leads to dev->dma_pfn_offset is set nonzero. To handle such
cases take dma_pfn_offset into account.

Cc: Joerg Roedel <jroedel@suse.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Reported-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Andras Szemzo <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 lib/dma-noop.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/lib/dma-noop.c b/lib/dma-noop.c
index 3d766e7..a14eee5 100644
--- a/lib/dma-noop.c
+++ b/lib/dma-noop.c
@@ -7,6 +7,7 @@
 #include <linux/mm.h>
 #include <linux/dma-mapping.h>
 #include <linux/scatterlist.h>
+#include <linux/pfn.h>
 
 static void *dma_noop_alloc(struct device *dev, size_t size,
 			    dma_addr_t *dma_handle, gfp_t gfp,
@@ -16,7 +17,8 @@ static void *dma_noop_alloc(struct device *dev, size_t size,
 
 	ret = (void *)__get_free_pages(gfp, get_order(size));
 	if (ret)
-		*dma_handle = virt_to_phys(ret);
+		*dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);
+
 	return ret;
 }
 
@@ -32,7 +34,7 @@ static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
 				      enum dma_data_direction dir,
 				      unsigned long attrs)
 {
-	return page_to_phys(page) + offset;
+	return page_to_phys(page) + offset - PFN_PHYS(dev->dma_pfn_offset);
 }
 
 static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
@@ -47,7 +49,7 @@ static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nent
 
 		BUG_ON(!sg_page(sg));
 		va = sg_virt(sg);
-		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
+		sg_dma_address(sg) = (dma_addr_t)(virt_to_phys(va) - PFN_PHYS(dev->dma_pfn_offset));
 		sg_dma_len(sg) = sg->length;
 	}
 
-- 
2.0.0

[PATCH 2/7] dma: Add simple dma_noop_mmap

[Vladimir Murzin]

This patch adds a simple implementation of mmap to dma_noop_ops.

Cc: Joerg Roedel <jroedel@suse.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Reported-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Andras Szemzo <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 lib/dma-noop.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/lib/dma-noop.c b/lib/dma-noop.c
index a14eee5..70504eb 100644
--- a/lib/dma-noop.c
+++ b/lib/dma-noop.c
@@ -66,6 +66,26 @@ static int dma_noop_supported(struct device *dev, u64 mask)
 	return 1;
 }
 
+static int dma_noop_mmap(struct device *dev, struct vm_area_struct *vma,
+			 void *cpu_addr, dma_addr_t dma_addr, size_t size,
+			 unsigned long attrs)
+{
+	unsigned long user_count = vma_pages(vma);
+	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+	unsigned long pfn = page_to_pfn(virt_to_page(cpu_addr));
+	unsigned long off = vma->vm_pgoff;
+	int ret = -ENXIO;
+
+	if (off < count && user_count <= (count - off)) {
+		ret = remap_pfn_range(vma, vma->vm_start,
+				      pfn + off,
+				      user_count << PAGE_SHIFT,
+				      vma->vm_page_prot);
+	}
+
+	return ret;
+}
+
 struct dma_map_ops dma_noop_ops = {
 	.alloc			= dma_noop_alloc,
 	.free			= dma_noop_free,
@@ -73,6 +93,7 @@ struct dma_map_ops dma_noop_ops = {
 	.map_sg			= dma_noop_map_sg,
 	.mapping_error		= dma_noop_mapping_error,
 	.dma_supported		= dma_noop_supported,
+	.mmap			= dma_noop_mmap,
 };
 
 EXPORT_SYMBOL(dma_noop_ops);
-- 
2.0.0

[PATCH 3/7] drivers: dma-coherent: Account dma_pfn_offset when used with device tree

[Vladimir Murzin]

dma_declare_coherent_memory() and friends are designed to account
difference in CPU and device addresses. However, when it is used with
reserved memory regions there is assumption that CPU and device have
the same view on address space. This assumption gets invalid when
reserved memory for coherent DMA allocations is referenced by device
with non-empty "dma-range" property.

Simply feeding device address as rmem->base + dev->dma_pfn_offset
would not work due to reserved memory region can be shared, so this
patch turns device address to be expressed with help of CPU address
and device's dma_pfn_offset.

For the case where device tree is not used and device sees memory
different to CPU we explicitly set device's dma_pfn_offset to
accomplish such difference. The latter might look controversial, but
it seems only a few drivers set device address different to CPU's:
- drivers/usb/host/ohci-sm501.c
- arch/sh/drivers/pci/fixups-dreamcast.c
so they can be screwed only if dma_pfn_offset there is set and not in
sync with device address range - we try to catch such cases with
WARN_ON.

Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Roger Quadros <rogerq@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Andras Szemzo <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 drivers/base/dma-coherent.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index 640a7e6..c59708c 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -18,6 +18,12 @@ struct dma_coherent_mem {
 	spinlock_t	spinlock;
 };
 
+static inline dma_addr_t dma_get_device_base(struct device *dev,
+					     struct dma_coherent_mem * mem)
+{
+	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
+}
+
 static bool dma_init_coherent_memory(
 	phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags,
 	struct dma_coherent_mem **mem)
@@ -83,9 +89,16 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
 static int dma_assign_coherent_memory(struct device *dev,
 				      struct dma_coherent_mem *mem)
 {
+	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
+
 	if (dev->dma_mem)
 		return -EBUSY;
 
+	if (dev->dma_pfn_offset)
+		WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset != dma_pfn_offset));
+	else
+		dev->dma_pfn_offset = dma_pfn_offset;
+
 	dev->dma_mem = mem;
 	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
 
@@ -133,7 +146,7 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
 		return ERR_PTR(-EINVAL);
 
 	spin_lock_irqsave(&mem->spinlock, flags);
-	pos = (device_addr - mem->device_base) >> PAGE_SHIFT;
+	pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
 	err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
 	spin_unlock_irqrestore(&mem->spinlock, flags);
 
@@ -186,7 +199,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
 	/*
 	 * Memory was found in the per-device area.
 	 */
-	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
+	*dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
 	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
 	dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
 	spin_unlock_irqrestore(&mem->spinlock, flags);
-- 
2.0.0

[PATCH 4/7] drivers: dma-coherent: Introduce default DMA pool

[Vladimir Murzin]

This patch introduces default coherent DMA pool similar to default CMA
area concept. To keep other users safe code kept under CONFIG_ARM.

Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Andras Szemzo <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 .../bindings/reserved-memory/reserved-memory.txt   |  3 ++
 drivers/base/dma-coherent.c                        | 59 +++++++++++++++++++---
 2 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
index 3da0ebd..16291f2 100644
--- a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+++ b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
@@ -68,6 +68,9 @@ Linux implementation note:
 - If a "linux,cma-default" property is present, then Linux will use the
   region for the default pool of the contiguous memory allocator.
 
+- If a "linux,dma-default" property is present, then Linux will use the
+  region for the default pool of the consistent DMA allocator.
+
 Device node references to reserved memory
 -----------------------------------------
 Regions in the /reserved-memory node may be referenced by other device
diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index c59708c..0c577ea 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -18,6 +18,15 @@ struct dma_coherent_mem {
 	spinlock_t	spinlock;
 };
 
+static struct dma_coherent_mem *dma_coherent_default_memory __ro_after_init;
+
+static inline struct dma_coherent_mem *dev_get_coherent_memory(struct device *dev)
+{
+	if (dev && dev->dma_mem)
+		return dev->dma_mem;
+	return dma_coherent_default_memory;
+}
+
 static inline dma_addr_t dma_get_device_base(struct device *dev,
 					     struct dma_coherent_mem * mem)
 {
@@ -91,6 +100,9 @@ static int dma_assign_coherent_memory(struct device *dev,
 {
 	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
 
+	if (!dev)
+		return -ENODEV;
+
 	if (dev->dma_mem)
 		return -EBUSY;
 
@@ -174,15 +186,12 @@ EXPORT_SYMBOL(dma_mark_declared_memory_occupied);
 int dma_alloc_from_coherent(struct device *dev, ssize_t size,
 				       dma_addr_t *dma_handle, void **ret)
 {
-	struct dma_coherent_mem *mem;
+	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);
 	int order = get_order(size);
 	unsigned long flags;
 	int pageno;
 	int dma_memory_map;
 
-	if (!dev)
-		return 0;
-	mem = dev->dma_mem;
 	if (!mem)
 		return 0;
 
@@ -236,7 +245,7 @@ EXPORT_SYMBOL(dma_alloc_from_coherent);
  */
 int dma_release_from_coherent(struct device *dev, int order, void *vaddr)
 {
-	struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;
+	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);
 
 	if (mem && vaddr >= mem->virt_base && vaddr <
 		   (mem->virt_base + (mem->size << PAGE_SHIFT))) {
@@ -270,7 +279,7 @@ EXPORT_SYMBOL(dma_release_from_coherent);
 int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
 			   void *vaddr, size_t size, int *ret)
 {
-	struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;
+	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);
 
 	if (mem && vaddr >= mem->virt_base && vaddr + size <=
 		   (mem->virt_base + (mem->size << PAGE_SHIFT))) {
@@ -300,6 +309,8 @@ EXPORT_SYMBOL(dma_mmap_from_coherent);
 #include <linux/of_fdt.h>
 #include <linux/of_reserved_mem.h>
 
+static struct reserved_mem *dma_reserved_default_memory __initdata;
+
 static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev)
 {
 	struct dma_coherent_mem *mem = rmem->priv;
@@ -320,7 +331,8 @@ static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev)
 static void rmem_dma_device_release(struct reserved_mem *rmem,
 				    struct device *dev)
 {
-	dev->dma_mem = NULL;
+	if (dev)
+		dev->dma_mem = NULL;
 }
 
 static const struct reserved_mem_ops rmem_dma_ops = {
@@ -340,6 +352,12 @@ static int __init rmem_dma_setup(struct reserved_mem *rmem)
 		pr_err("Reserved memory: regions without no-map are not yet supported\n");
 		return -EINVAL;
 	}
+
+	if (of_get_flat_dt_prop(node, "linux,dma-default", NULL)) {
+		WARN(dma_reserved_default_memory,
+		     "Reserved memory: region for default DMA coherent area is redefined\n");
+		dma_reserved_default_memory = rmem;
+	}
 #endif
 
 	rmem->ops = &rmem_dma_ops;
@@ -347,5 +365,32 @@ static int __init rmem_dma_setup(struct reserved_mem *rmem)
 		&rmem->base, (unsigned long)rmem->size / SZ_1M);
 	return 0;
 }
+
+static int __init dma_init_reserved_memory(void)
+{
+	const struct reserved_mem_ops *ops;
+	int ret;
+
+	if (!dma_reserved_default_memory)
+		return -ENOMEM;
+
+	ops = dma_reserved_default_memory->ops;
+
+	/*
+	 * We rely on rmem_dma_device_init() does not propagate error of
+	 * dma_assign_coherent_memory() for "NULL" device.
+	 */
+	ret = ops->device_init(dma_reserved_default_memory, NULL);
+
+	if (!ret) {
+		dma_coherent_default_memory = dma_reserved_default_memory->priv;
+		pr_info("DMA: default coherent area is set\n");
+	}
+
+	return ret;
+}
+
+core_initcall(dma_init_reserved_memory);
+
 RESERVEDMEM_OF_DECLARE(dma, "shared-dma-pool", rmem_dma_setup);
 #endif
-- 
2.0.0

[PATCH 5/7] ARM: NOMMU: Introduce dma operations for noMMU

[Vladimir Murzin]

R/M classes of cpus can have memory covered by MPU which in turn might
configure RAM as Normal i.e. bufferable and cacheable. It breaks
dma_alloc_coherent() and friends, since data can stuck in caches now
or be buffered.

This patch factors out DMA support for NOMMU configuration into
separate entity which provides dedicated dma_ops. We have to handle
there several cases:
- configurations with MMU/MPU setup
- configurations without MMU/MPU setup
- special case for M-class, since caches and MPU there are optional

In general we rely on default DMA area for coherent allocations or/and
per-device memory reserves suitable for coherent DMA, so if such
regions are set coherent allocations go from there.

In case MPU/MPU was not setup we fallback to normal page allocator for
DMA memory allocation.

In case we run M-class cpus, for configuration without cache support
(like Cortex-M3/M4) dma operations are forced to be coherent and wired
with dma-noop (such decision is made based on cacheid global
variable); however, if caches are detected there and no DMA coherent
region is given (either default or per-device), dma is disallowed even
MPU is not set - it is because M-class implement system memory map
which defines part of address space as Normal memory.

Reported-by: Alexandre Torgue <alexandre.torgue@st.com>
Reported-by: Andras Szemzo <sza@esh.hu>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Andras Szemzo <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/arm/include/asm/dma-mapping.h |   3 +-
 arch/arm/mm/Makefile               |   5 +-
 arch/arm/mm/dma-mapping-nommu.c    | 253 +++++++++++++++++++++++++++++++++++++
 3 files changed, 257 insertions(+), 4 deletions(-)
 create mode 100644 arch/arm/mm/dma-mapping-nommu.c

diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index bf02dbd..559faad 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -20,7 +20,8 @@ static inline struct dma_map_ops *__generic_dma_ops(struct device *dev)
 {
 	if (dev && dev->archdata.dma_ops)
 		return dev->archdata.dma_ops;
-	return &arm_dma_ops;
+
+	return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : &dma_noop_ops;
 }
 
 static inline struct dma_map_ops *get_dma_ops(struct device *dev)
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index 2ac7988..5796357 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -2,9 +2,8 @@
 # Makefile for the linux arm-specific parts of the memory manager.
 #
 
-obj-y				:= dma-mapping.o extable.o fault.o init.o \
-				   iomap.o
-
+obj-y				:= extable.o fault.o init.o iomap.o
+obj-y				+= dma-mapping$(MMUEXT).o
 obj-$(CONFIG_MMU)		+= fault-armv.o flush.o idmap.o ioremap.o \
 				   mmap.o pgd.o mmu.o pageattr.o
 
diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
new file mode 100644
index 0000000..1f86580
--- /dev/null
+++ b/arch/arm/mm/dma-mapping-nommu.c
@@ -0,0 +1,253 @@
+/*
+ *  Based on linux/arch/arm/mm/dma-mapping.c
+ *
+ *  Copyright (C) 2000-2004 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+
+#include <asm/cachetype.h>
+#include <asm/cacheflush.h>
+#include <asm/outercache.h>
+#include <asm/cp15.h>
+
+#include "dma.h"
+
+/*
+ *  dma_noop_ops is used if
+ *   - MMU/MPU is off
+ *   - cpu is v7m w/o cache support
+ *   - device is coherent
+ *  otherwise arm_nommu_dma_ops is used.
+ *
+ *  arm_nommu_dma_ops rely on consistent DMA memory (please, refer to
+ *  [1] on how to declare such memory).
+ *
+ *  [1] Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+ */
+
+static void *arm_nommu_dma_alloc(struct device *dev, size_t size,
+				 dma_addr_t *dma_handle, gfp_t gfp,
+				 unsigned long attrs)
+
+{
+	struct dma_map_ops *ops = &dma_noop_ops;
+
+	/*
+	 * We are here because:
+	 * - no consistent DMA region has been defined, so we can't
+	 *   continue.
+	 * - there is no space left in consistent DMA region, so we
+	 *   only can fallback to generic allocator if we are
+	 *   advertised that consistency is not required.
+	 */
+
+	if (attrs & DMA_ATTR_NON_CONSISTENT)
+		return ops->alloc(dev, size, dma_handle, gfp, attrs);
+
+	WARN_ON_ONCE(1);
+	return NULL;
+}
+
+static void arm_nommu_dma_free(struct device *dev, size_t size,
+			       void *cpu_addr, dma_addr_t dma_addr,
+			       unsigned long attrs)
+{
+	struct dma_map_ops *ops = &dma_noop_ops;
+
+	if (attrs & DMA_ATTR_NON_CONSISTENT)
+		ops->free(dev, size, cpu_addr, dma_addr, attrs);
+	else
+		WARN_ON_ONCE(1);
+
+	return;
+}
+
+static int arm_nommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+			      void *cpu_addr, dma_addr_t dma_addr, size_t size,
+			      unsigned long attrs)
+{
+	struct dma_map_ops *ops = &dma_noop_ops;
+	int ret;
+
+	if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
+		return ret;
+
+	if (attrs & DMA_ATTR_NON_CONSISTENT)
+		return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
+
+	WARN_ON_ONCE(1);
+	return -ENXIO;
+}
+
+static void __dma_page_cpu_to_dev(phys_addr_t paddr, size_t size,
+				  enum dma_data_direction dir)
+{
+	dmac_map_area(__va(paddr), size, dir);
+
+	if (dir == DMA_FROM_DEVICE)
+		outer_inv_range(paddr, paddr + size);
+	else
+		outer_clean_range(paddr, paddr + size);
+}
+
+static void __dma_page_dev_to_cpu(phys_addr_t paddr, size_t size,
+				  enum dma_data_direction dir)
+{
+	if (dir != DMA_TO_DEVICE) {
+		outer_inv_range(paddr, paddr + size);
+		dmac_unmap_area(__va(paddr), size, dir);
+	}
+}
+
+static dma_addr_t arm_nommu_dma_map_page(struct device *dev, struct page *page,
+					 unsigned long offset, size_t size,
+					 enum dma_data_direction dir,
+					 unsigned long attrs)
+{
+	dma_addr_t handle = page_to_phys(page) + offset;
+
+	__dma_page_cpu_to_dev(handle, size, dir);
+
+	return handle;
+}
+
+static void arm_nommu_dma_unmap_page(struct device *dev, dma_addr_t handle,
+				     size_t size, enum dma_data_direction dir,
+				     unsigned long attrs)
+{
+	__dma_page_dev_to_cpu(handle, size, dir);
+}
+
+
+static int arm_nommu_dma_map_sg(struct device *dev, struct scatterlist *sgl,
+				int nents, enum dma_data_direction dir,
+				unsigned long attrs)
+{
+	int i;
+	struct scatterlist *sg;
+
+	for_each_sg(sgl, sg, nents, i) {
+		sg_dma_address(sg) = sg_phys(sg);
+		sg_dma_len(sg) = sg->length;
+		__dma_page_cpu_to_dev(sg_dma_address(sg), sg_dma_len(sg), dir);
+	}
+
+	return nents;
+}
+
+static void arm_nommu_dma_unmap_sg(struct device *dev, struct scatterlist *sgl,
+				   int nents, enum dma_data_direction dir,
+				   unsigned long attrs)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nents, i)
+		__dma_page_dev_to_cpu(sg_dma_address(sg), sg_dma_len(sg), dir);
+}
+
+static void arm_nommu_dma_sync_single_for_device(struct device *dev,
+		dma_addr_t handle, size_t size, enum dma_data_direction dir)
+{
+	__dma_page_cpu_to_dev(handle, size, dir);
+}
+
+static void arm_nommu_dma_sync_single_for_cpu(struct device *dev,
+		dma_addr_t handle, size_t size, enum dma_data_direction dir)
+{
+	__dma_page_cpu_to_dev(handle, size, dir);
+}
+
+static void arm_nommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
+					     int nents, enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nents, i)
+		__dma_page_cpu_to_dev(sg_dma_address(sg), sg_dma_len(sg), dir);
+}
+
+static void arm_nommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
+					  int nents, enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nents, i)
+		__dma_page_dev_to_cpu(sg_dma_address(sg), sg_dma_len(sg), dir);
+}
+
+struct dma_map_ops arm_nommu_dma_ops = {
+	.alloc			= arm_nommu_dma_alloc,
+	.free			= arm_nommu_dma_free,
+	.mmap			= arm_nommu_dma_mmap,
+	.map_page		= arm_nommu_dma_map_page,
+	.unmap_page		= arm_nommu_dma_unmap_page,
+	.map_sg			= arm_nommu_dma_map_sg,
+	.unmap_sg		= arm_nommu_dma_unmap_sg,
+	.sync_single_for_device	= arm_nommu_dma_sync_single_for_device,
+	.sync_single_for_cpu	= arm_nommu_dma_sync_single_for_cpu,
+	.sync_sg_for_device	= arm_nommu_dma_sync_sg_for_device,
+	.sync_sg_for_cpu	= arm_nommu_dma_sync_sg_for_cpu,
+};
+EXPORT_SYMBOL(arm_nommu_dma_ops);
+
+static struct dma_map_ops *arm_nommu_get_dma_map_ops(bool coherent)
+{
+	return coherent ? &dma_noop_ops : &arm_nommu_dma_ops;
+}
+
+void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+			const struct iommu_ops *iommu, bool coherent)
+{
+	struct dma_map_ops *dma_ops;
+
+	if (IS_ENABLED(CONFIG_CPU_V7M)) {
+		/*
+		 * Cache support for v7m is optional, so can be treated as
+		 * coherent if no cache has been detected. Note that it is not
+		 * enough to check if MPU is in use or not since in absense of
+		 * MPU system memory map is used.
+		 */
+		dev->archdata.dma_coherent = (cacheid) ? coherent : true;
+	} else {
+		/*
+		 * Assume coherent DMA in case MMU/MPU has not been set up.
+		 */
+		dev->archdata.dma_coherent = (get_cr() & CR_M) ? coherent : true;
+	}
+
+	dma_ops = arm_nommu_get_dma_map_ops(dev->archdata.dma_coherent);
+
+	set_dma_ops(dev, dma_ops);
+}
+
+void arch_teardown_dma_ops(struct device *dev)
+{
+}
+
+int dma_supported(struct device *dev, u64 mask)
+{
+	return 1;
+}
+
+EXPORT_SYMBOL(dma_supported);
+
+#define PREALLOC_DMA_DEBUG_ENTRIES	4096
+
+static int __init dma_debug_do_init(void)
+{
+	dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
+	return 0;
+}
+core_initcall(dma_debug_do_init);
-- 
2.0.0

[PATCH 6/7] ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus

[Vladimir Murzin]

Now, we have dedicated non-cacheable region for consistent DMA
operations. However, that region can still be marked as bufferable by
MPU, so it'd be safer to have barriers by default.

Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Andras Szemzo <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/arm/mm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 0b79f12..64a1465c 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1029,7 +1029,7 @@ config ARM_L1_CACHE_SHIFT
 
 config ARM_DMA_MEM_BUFFERABLE
 	bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
-	default y if CPU_V6 || CPU_V6K || CPU_V7
+	default y if CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M
 	help
 	  Historically, the kernel has used strongly ordered mappings to
 	  provide DMA coherent memory.  With the advent of ARMv7, mapping
-- 
2.0.0

[PATCH 7/7] ARM: dma-mapping: Remove traces of NOMMU code

[Vladimir Murzin]

DMA operations for NOMMU case have been just factored out into
separate compilation unit, so don't keep dead code.

Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Andras Szemzo <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/arm/mm/dma-mapping.c | 26 ++------------------------
 1 file changed, 2 insertions(+), 24 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index ab77100..d8a755b 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -344,8 +344,6 @@ static void __dma_free_buffer(struct page *page, size_t size)
 	}
 }
 
-#ifdef CONFIG_MMU
-
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
 				     pgprot_t prot, struct page **ret_page,
 				     const void *caller, bool want_vaddr,
@@ -646,22 +644,6 @@ static inline pgprot_t __get_dma_pgprot(unsigned long attrs, pgprot_t prot)
 	return prot;
 }
 
-#define nommu() 0
-
-#else	/* !CONFIG_MMU */
-
-#define nommu() 1
-
-#define __get_dma_pgprot(attrs, prot)				__pgprot(0)
-#define __alloc_remap_buffer(dev, size, gfp, prot, ret, c, wv)	NULL
-#define __alloc_from_pool(size, ret_page)			NULL
-#define __alloc_from_contiguous(dev, size, prot, ret, c, wv, coherent_flag)	NULL
-#define __free_from_pool(cpu_addr, size)			do { } while (0)
-#define __free_from_contiguous(dev, page, cpu_addr, size, wv)	do { } while (0)
-#define __dma_free_remap(cpu_addr, size)			do { } while (0)
-
-#endif	/* CONFIG_MMU */
-
 static void *__alloc_simple_buffer(struct device *dev, size_t size, gfp_t gfp,
 				   struct page **ret_page)
 {
@@ -803,7 +785,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 
 	if (cma)
 		buf->allocator = &cma_allocator;
-	else if (nommu() || is_coherent)
+	else if (is_coherent)
 		buf->allocator = &simple_allocator;
 	else if (allowblock)
 		buf->allocator = &remap_allocator;
@@ -852,8 +834,7 @@ static int __arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 		 void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		 unsigned long attrs)
 {
-	int ret = -ENXIO;
-#ifdef CONFIG_MMU
+	int ret;
 	unsigned long nr_vma_pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	unsigned long pfn = dma_to_pfn(dev, dma_addr);
@@ -868,7 +849,6 @@ static int __arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 				      vma->vm_end - vma->vm_start,
 				      vma->vm_page_prot);
 	}
-#endif	/* CONFIG_MMU */
 
 	return ret;
 }
@@ -887,9 +867,7 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 		 void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		 unsigned long attrs)
 {
-#ifdef CONFIG_MMU
 	vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
-#endif	/* CONFIG_MMU */
 	return __arm_dma_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
 }
 
-- 
2.0.0

[PATCH 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU

[Vladimir Murzin]

Gentle ping!

Cc: Joerg Roedel <jroedel@suse.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Roger Quadros <rogerq@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>

On 15/02/17 09:59, Vladimir Murzin wrote:
> Hi,
> 
> It seem that addition of cache support for M-class CPUs uncovered
> latent bug in DMA usage. NOMMU memory model has been treated as being
> always consistent; however, for R/M CPU classes memory can be covered
> by MPU which in turn might configure RAM as Normal i.e. bufferable and
> cacheable. It breaks dma_alloc_coherent() and friends, since data can
> stuck in caches now or be buffered.
> 
> This patch set is trying to address the issue by providing region of
> memory suitable for consistent DMA operations. It is supposed that
> such region is marked by MPU as non-cacheable. Robin suggested to
> advertise such memory as reserved shared-dma-pool, rather then using
> homebrew command line option, and extend dma-coherent to provide
> default DMA area in the similar way as it is done for CMA (PATCH
> 4/7). It allows us to offload all bookkeeping on generic coherent DMA
> framework, and it seems that it might be reused by other architectures
> like c6x and blackfin.
> 
> While reviewing/testing previous vesrions of the patch set it turned
> out that dma-coherent does not take into account "dma-ranges" device
> tree property, so it is addressed in PATCH 3/7.
> 
> For ARM, dedicated DMA region is required for cases other than:
>  - MMU/MPU is off
>  - cpu is v7m w/o cache support
>  - device is coherent
> 
> In case one of the above conditions is true dma operations are forced
> to be coherent and wired with dma_noop_ops.
> 
> To make life easier NOMMU dma operations are kept in separate
> compilation unit.
> 
> Since the issue was reported in the same time as Benjamin sent his
> patch [1] to allow mmap for NOMMU, his case is also addressed in this
> series (PATCH 1/7 and PATCH 2/7).
> 
> Thanks!
> 
> [1] http://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8633/1
> 
> Changelog:
> 	RFC v6 -> v1
> 	       - dropped RFC tag
> 	       - added Alexandre's Tested-by
> 
> Vladimir Murzin (7):
>   dma: Take into account dma_pfn_offset
>   dma: Add simple dma_noop_mmap
>   drivers: dma-coherent: Account dma_pfn_offset when used with device
>     tree
>   drivers: dma-coherent: Introduce default DMA pool
>   ARM: NOMMU: Introduce dma operations for noMMU
>   ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus
>   ARM: dma-mapping: Remove traces of NOMMU code
> 
>  .../bindings/reserved-memory/reserved-memory.txt   |   3 +
>  arch/arm/include/asm/dma-mapping.h                 |   3 +-
>  arch/arm/mm/Kconfig                                |   2 +-
>  arch/arm/mm/Makefile                               |   5 +-
>  arch/arm/mm/dma-mapping-nommu.c                    | 253 +++++++++++++++++++++
>  arch/arm/mm/dma-mapping.c                          |  26 +--
>  drivers/base/dma-coherent.c                        |  76 ++++++-
>  lib/dma-noop.c                                     |  29 ++-
>  8 files changed, 356 insertions(+), 41 deletions(-)
>  create mode 100644 arch/arm/mm/dma-mapping-nommu.c
> 

[PATCH 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU

[Robin Murphy]

Hi Vladimir,

On 21/02/17 10:41, Vladimir Murzin wrote:
> Gentle ping!

What's your plan for this series? Are you looking for acks on the common
parts to take it through the ARM tree, or Russell's ack on the ARM parts
for it to go through mm?

Either way, I expect the merge window is probably consuming most folks'
attention just now.

Robin.

> Cc: Joerg Roedel <jroedel@suse.de>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Alan Stern <stern@rowland.harvard.edu>
> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
> Cc: Rich Felker <dalias@libc.org>
> Cc: Roger Quadros <rogerq@ti.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> 
> On 15/02/17 09:59, Vladimir Murzin wrote:
>> Hi,
>>
>> It seem that addition of cache support for M-class CPUs uncovered
>> latent bug in DMA usage. NOMMU memory model has been treated as being
>> always consistent; however, for R/M CPU classes memory can be covered
>> by MPU which in turn might configure RAM as Normal i.e. bufferable and
>> cacheable. It breaks dma_alloc_coherent() and friends, since data can
>> stuck in caches now or be buffered.
>>
>> This patch set is trying to address the issue by providing region of
>> memory suitable for consistent DMA operations. It is supposed that
>> such region is marked by MPU as non-cacheable. Robin suggested to
>> advertise such memory as reserved shared-dma-pool, rather then using
>> homebrew command line option, and extend dma-coherent to provide
>> default DMA area in the similar way as it is done for CMA (PATCH
>> 4/7). It allows us to offload all bookkeeping on generic coherent DMA
>> framework, and it seems that it might be reused by other architectures
>> like c6x and blackfin.
>>
>> While reviewing/testing previous vesrions of the patch set it turned
>> out that dma-coherent does not take into account "dma-ranges" device
>> tree property, so it is addressed in PATCH 3/7.
>>
>> For ARM, dedicated DMA region is required for cases other than:
>>  - MMU/MPU is off
>>  - cpu is v7m w/o cache support
>>  - device is coherent
>>
>> In case one of the above conditions is true dma operations are forced
>> to be coherent and wired with dma_noop_ops.
>>
>> To make life easier NOMMU dma operations are kept in separate
>> compilation unit.
>>
>> Since the issue was reported in the same time as Benjamin sent his
>> patch [1] to allow mmap for NOMMU, his case is also addressed in this
>> series (PATCH 1/7 and PATCH 2/7).
>>
>> Thanks!
>>
>> [1] http://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8633/1
>>
>> Changelog:
>> 	RFC v6 -> v1
>> 	       - dropped RFC tag
>> 	       - added Alexandre's Tested-by
>>
>> Vladimir Murzin (7):
>>   dma: Take into account dma_pfn_offset
>>   dma: Add simple dma_noop_mmap
>>   drivers: dma-coherent: Account dma_pfn_offset when used with device
>>     tree
>>   drivers: dma-coherent: Introduce default DMA pool
>>   ARM: NOMMU: Introduce dma operations for noMMU
>>   ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus
>>   ARM: dma-mapping: Remove traces of NOMMU code
>>
>>  .../bindings/reserved-memory/reserved-memory.txt   |   3 +
>>  arch/arm/include/asm/dma-mapping.h                 |   3 +-
>>  arch/arm/mm/Kconfig                                |   2 +-
>>  arch/arm/mm/Makefile                               |   5 +-
>>  arch/arm/mm/dma-mapping-nommu.c                    | 253 +++++++++++++++++++++
>>  arch/arm/mm/dma-mapping.c                          |  26 +--
>>  drivers/base/dma-coherent.c                        |  76 ++++++-
>>  lib/dma-noop.c                                     |  29 ++-
>>  8 files changed, 356 insertions(+), 41 deletions(-)
>>  create mode 100644 arch/arm/mm/dma-mapping-nommu.c
>>
> 

[PATCH 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU

[Vladimir Murzin]

Hi Robin,

On 21/02/17 12:16, Robin Murphy wrote:
> Hi Vladimir,
> 
> On 21/02/17 10:41, Vladimir Murzin wrote:
>> Gentle ping!
> 
> What's your plan for this series? Are you looking for acks on the common
> parts to take it through the ARM tree, or Russell's ack on the ARM parts
> for it to go through mm?

Nothing particular in my mind - either way would work me. So far I have not
heard feedback on common parts and it is not clear to me who should give Ack
on them :(

> 
> Either way, I expect the merge window is probably consuming most folks'
> attention just now.

I see.

Cheers
Vladimir

> 
> Robin.
> 
>> Cc: Joerg Roedel <jroedel@suse.de>
>> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
>> Cc: Michal Nazarewicz <mina86@mina86.com>
>> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
>> Cc: Alan Stern <stern@rowland.harvard.edu>
>> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
>> Cc: Rich Felker <dalias@libc.org>
>> Cc: Roger Quadros <rogerq@ti.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Rob Herring <robh+dt@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>>
>> On 15/02/17 09:59, Vladimir Murzin wrote:
>>> Hi,
>>>
>>> It seem that addition of cache support for M-class CPUs uncovered
>>> latent bug in DMA usage. NOMMU memory model has been treated as being
>>> always consistent; however, for R/M CPU classes memory can be covered
>>> by MPU which in turn might configure RAM as Normal i.e. bufferable and
>>> cacheable. It breaks dma_alloc_coherent() and friends, since data can
>>> stuck in caches now or be buffered.
>>>
>>> This patch set is trying to address the issue by providing region of
>>> memory suitable for consistent DMA operations. It is supposed that
>>> such region is marked by MPU as non-cacheable. Robin suggested to
>>> advertise such memory as reserved shared-dma-pool, rather then using
>>> homebrew command line option, and extend dma-coherent to provide
>>> default DMA area in the similar way as it is done for CMA (PATCH
>>> 4/7). It allows us to offload all bookkeeping on generic coherent DMA
>>> framework, and it seems that it might be reused by other architectures
>>> like c6x and blackfin.
>>>
>>> While reviewing/testing previous vesrions of the patch set it turned
>>> out that dma-coherent does not take into account "dma-ranges" device
>>> tree property, so it is addressed in PATCH 3/7.
>>>
>>> For ARM, dedicated DMA region is required for cases other than:
>>>  - MMU/MPU is off
>>>  - cpu is v7m w/o cache support
>>>  - device is coherent
>>>
>>> In case one of the above conditions is true dma operations are forced
>>> to be coherent and wired with dma_noop_ops.
>>>
>>> To make life easier NOMMU dma operations are kept in separate
>>> compilation unit.
>>>
>>> Since the issue was reported in the same time as Benjamin sent his
>>> patch [1] to allow mmap for NOMMU, his case is also addressed in this
>>> series (PATCH 1/7 and PATCH 2/7).
>>>
>>> Thanks!
>>>
>>> [1] http://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8633/1
>>>
>>> Changelog:
>>> 	RFC v6 -> v1
>>> 	       - dropped RFC tag
>>> 	       - added Alexandre's Tested-by
>>>
>>> Vladimir Murzin (7):
>>>   dma: Take into account dma_pfn_offset
>>>   dma: Add simple dma_noop_mmap
>>>   drivers: dma-coherent: Account dma_pfn_offset when used with device
>>>     tree
>>>   drivers: dma-coherent: Introduce default DMA pool
>>>   ARM: NOMMU: Introduce dma operations for noMMU
>>>   ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus
>>>   ARM: dma-mapping: Remove traces of NOMMU code
>>>
>>>  .../bindings/reserved-memory/reserved-memory.txt   |   3 +
>>>  arch/arm/include/asm/dma-mapping.h                 |   3 +-
>>>  arch/arm/mm/Kconfig                                |   2 +-
>>>  arch/arm/mm/Makefile                               |   5 +-
>>>  arch/arm/mm/dma-mapping-nommu.c                    | 253 +++++++++++++++++++++
>>>  arch/arm/mm/dma-mapping.c                          |  26 +--
>>>  drivers/base/dma-coherent.c                        |  76 ++++++-
>>>  lib/dma-noop.c                                     |  29 ++-
>>>  8 files changed, 356 insertions(+), 41 deletions(-)
>>>  create mode 100644 arch/arm/mm/dma-mapping-nommu.c
>>>
>>
> 
> 

[PATCH 3/7] drivers: dma-coherent: Account dma_pfn_offset when used with device tree

[Robin Murphy]

On 15/02/17 09:59, Vladimir Murzin wrote:
> dma_declare_coherent_memory() and friends are designed to account
> difference in CPU and device addresses. However, when it is used with
> reserved memory regions there is assumption that CPU and device have
> the same view on address space. This assumption gets invalid when
> reserved memory for coherent DMA allocations is referenced by device
> with non-empty "dma-range" property.
> 
> Simply feeding device address as rmem->base + dev->dma_pfn_offset
> would not work due to reserved memory region can be shared, so this
> patch turns device address to be expressed with help of CPU address
> and device's dma_pfn_offset.
> 
> For the case where device tree is not used and device sees memory
> different to CPU we explicitly set device's dma_pfn_offset to
> accomplish such difference. The latter might look controversial, but
> it seems only a few drivers set device address different to CPU's:
> - drivers/usb/host/ohci-sm501.c
> - arch/sh/drivers/pci/fixups-dreamcast.c
> so they can be screwed only if dma_pfn_offset there is set and not in
> sync with device address range - we try to catch such cases with
> WARN_ON.
> 
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Alan Stern <stern@rowland.harvard.edu>
> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
> Cc: Rich Felker <dalias@libc.org>
> Cc: Roger Quadros <rogerq@ti.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Tested-by: Andras Szemzo <sza@esh.hu>
> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> ---
>  drivers/base/dma-coherent.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
> index 640a7e6..c59708c 100644
> --- a/drivers/base/dma-coherent.c
> +++ b/drivers/base/dma-coherent.c
> @@ -18,6 +18,12 @@ struct dma_coherent_mem {
>  	spinlock_t	spinlock;
>  };
>  
> +static inline dma_addr_t dma_get_device_base(struct device *dev,
> +					     struct dma_coherent_mem * mem)
> +{
> +	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
> +}
> +
>  static bool dma_init_coherent_memory(
>  	phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags,
>  	struct dma_coherent_mem **mem)
> @@ -83,9 +89,16 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
>  static int dma_assign_coherent_memory(struct device *dev,
>  				      struct dma_coherent_mem *mem)
>  {
> +	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
> +
>  	if (dev->dma_mem)
>  		return -EBUSY;
>  
> +	if (dev->dma_pfn_offset)
> +		WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset != dma_pfn_offset));
> +	else
> +		dev->dma_pfn_offset = dma_pfn_offset;

This makes me rather uneasy - I can well imagine a device sharing the
CPU physical address map of external system memory, but having its own
view of its local coherent memory such that pfn_base != device_base
still. I know for a fact we've had internal FPGA tiles set up that way,
although whether it was entirely intentional is another matter... ;)

In that situation, setting dev->dma_pfn_offset like this would break
streaming DMA for such devices. Could we not keep the pool-specific
offset and the device-specific offset independent, apply whichever is
non-zero, and scream if both are set?

Robin.

> +
>  	dev->dma_mem = mem;
>  	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
>  
> @@ -133,7 +146,7 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
>  		return ERR_PTR(-EINVAL);
>  
>  	spin_lock_irqsave(&mem->spinlock, flags);
> -	pos = (device_addr - mem->device_base) >> PAGE_SHIFT;
> +	pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
>  	err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
>  	spin_unlock_irqrestore(&mem->spinlock, flags);
>  
> @@ -186,7 +199,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
>  	/*
>  	 * Memory was found in the per-device area.
>  	 */
> -	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
> +	*dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
>  	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
>  	dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
>  	spin_unlock_irqrestore(&mem->spinlock, flags);
> 

[PATCH 6/7] ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus

[Robin Murphy]

On 15/02/17 09:59, Vladimir Murzin wrote:
> Now, we have dedicated non-cacheable region for consistent DMA
> operations. However, that region can still be marked as bufferable by
> MPU, so it'd be safer to have barriers by default.

Makes sense - plenty of cases want their DMA buffers to still be
write-combining (e.g. framebuffers have already been mentioned here),
for which strongly-ordered mappings won't do. Plus you don't exactly
have a choice if you've no MPU and have fixed Normal attributes for your
RAM region.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Tested-by: Andras Szemzo <sza@esh.hu>
> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> ---
>  arch/arm/mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index 0b79f12..64a1465c 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -1029,7 +1029,7 @@ config ARM_L1_CACHE_SHIFT
>  
>  config ARM_DMA_MEM_BUFFERABLE
>  	bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
> -	default y if CPU_V6 || CPU_V6K || CPU_V7
> +	default y if CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M
>  	help
>  	  Historically, the kernel has used strongly ordered mappings to
>  	  provide DMA coherent memory.  With the advent of ARMv7, mapping
> 

[PATCH 3/7] drivers: dma-coherent: Account dma_pfn_offset when used with device tree

[Vladimir Murzin]

On 21/02/17 12:37, Robin Murphy wrote:
> On 15/02/17 09:59, Vladimir Murzin wrote:
>> dma_declare_coherent_memory() and friends are designed to account
>> difference in CPU and device addresses. However, when it is used with
>> reserved memory regions there is assumption that CPU and device have
>> the same view on address space. This assumption gets invalid when
>> reserved memory for coherent DMA allocations is referenced by device
>> with non-empty "dma-range" property.
>>
>> Simply feeding device address as rmem->base + dev->dma_pfn_offset
>> would not work due to reserved memory region can be shared, so this
>> patch turns device address to be expressed with help of CPU address
>> and device's dma_pfn_offset.
>>
>> For the case where device tree is not used and device sees memory
>> different to CPU we explicitly set device's dma_pfn_offset to
>> accomplish such difference. The latter might look controversial, but
>> it seems only a few drivers set device address different to CPU's:
>> - drivers/usb/host/ohci-sm501.c
>> - arch/sh/drivers/pci/fixups-dreamcast.c
>> so they can be screwed only if dma_pfn_offset there is set and not in
>> sync with device address range - we try to catch such cases with
>> WARN_ON.
>>
>> Cc: Michal Nazarewicz <mina86@mina86.com>
>> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
>> Cc: Alan Stern <stern@rowland.harvard.edu>
>> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
>> Cc: Rich Felker <dalias@libc.org>
>> Cc: Roger Quadros <rogerq@ti.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
>> Tested-by: Andras Szemzo <sza@esh.hu>
>> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
>> ---
>>  drivers/base/dma-coherent.c | 17 +++++++++++++++--
>>  1 file changed, 15 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
>> index 640a7e6..c59708c 100644
>> --- a/drivers/base/dma-coherent.c
>> +++ b/drivers/base/dma-coherent.c
>> @@ -18,6 +18,12 @@ struct dma_coherent_mem {
>>  	spinlock_t	spinlock;
>>  };
>>  
>> +static inline dma_addr_t dma_get_device_base(struct device *dev,
>> +					     struct dma_coherent_mem * mem)
>> +{
>> +	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
>> +}
>> +
>>  static bool dma_init_coherent_memory(
>>  	phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags,
>>  	struct dma_coherent_mem **mem)
>> @@ -83,9 +89,16 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
>>  static int dma_assign_coherent_memory(struct device *dev,
>>  				      struct dma_coherent_mem *mem)
>>  {
>> +	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
>> +
>>  	if (dev->dma_mem)
>>  		return -EBUSY;
>>  
>> +	if (dev->dma_pfn_offset)
>> +		WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset != dma_pfn_offset));
>> +	else
>> +		dev->dma_pfn_offset = dma_pfn_offset;
> 
> This makes me rather uneasy - I can well imagine a device sharing the
> CPU physical address map of external system memory, but having its own
> view of its local coherent memory such that pfn_base != device_base
> still. I know for a fact we've had internal FPGA tiles set up that way,
> although whether it was entirely intentional is another matter... ;)
> 
> In that situation, setting dev->dma_pfn_offset like this would break
> streaming DMA for such devices. Could we not keep the pool-specific
> offset and the device-specific offset independent, apply whichever is
> non-zero, and scream if both are set?

Something like fixup bellow?

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index 0c577ea..2060010 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -30,7 +30,15 @@ static inline struct dma_coherent_mem *dev_get_coherent_memory(struct device *de
 static inline dma_addr_t dma_get_device_base(struct device *dev,
 					     struct dma_coherent_mem * mem)
 {
-	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
+	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
+
+	if (dma_pfn_offset != dev->dma_pfn_offset )
+		WARN_ON(device_pfn_offset && dev->dma_pfn_offset);
+
+	if (dma_pfn_offset)
+		return mem->device_base;
+	else
+		return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
 }
 
 static bool dma_init_coherent_memory(
@@ -98,19 +106,12 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
 static int dma_assign_coherent_memory(struct device *dev,
 				      struct dma_coherent_mem *mem)
 {
-	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
-
 	if (!dev)
 		return -ENODEV;
 
 	if (dev->dma_mem)
 		return -EBUSY;
 
-	if (dev->dma_pfn_offset)
-		WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset != dma_pfn_offset));
-	else
-		dev->dma_pfn_offset = dma_pfn_offset;
-
 	dev->dma_mem = mem;
 	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */


Cheers
Vladimir

> 
> Robin.
> 
>> +
>>  	dev->dma_mem = mem;
>>  	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
>>  
>> @@ -133,7 +146,7 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
>>  		return ERR_PTR(-EINVAL);
>>  
>>  	spin_lock_irqsave(&mem->spinlock, flags);
>> -	pos = (device_addr - mem->device_base) >> PAGE_SHIFT;
>> +	pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
>>  	err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
>>  	spin_unlock_irqrestore(&mem->spinlock, flags);
>>  
>> @@ -186,7 +199,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
>>  	/*
>>  	 * Memory was found in the per-device area.
>>  	 */
>> -	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
>> +	*dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
>>  	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
>>  	dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
>>  	spin_unlock_irqrestore(&mem->spinlock, flags);
>>
> 
> 

[PATCH 6/7] ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus

[Vladimir Murzin]

On 21/02/17 12:57, Robin Murphy wrote:
> On 15/02/17 09:59, Vladimir Murzin wrote:
>> Now, we have dedicated non-cacheable region for consistent DMA
>> operations. However, that region can still be marked as bufferable by
>> MPU, so it'd be safer to have barriers by default.
> 
> Makes sense - plenty of cases want their DMA buffers to still be
> write-combining (e.g. framebuffers have already been mentioned here),
> for which strongly-ordered mappings won't do. Plus you don't exactly
> have a choice if you've no MPU and have fixed Normal attributes for your
> RAM region.
> 
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>

Thanks!

Vladimir

> 
>> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
>> Tested-by: Andras Szemzo <sza@esh.hu>
>> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
>> ---
>>  arch/arm/mm/Kconfig | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
>> index 0b79f12..64a1465c 100644
>> --- a/arch/arm/mm/Kconfig
>> +++ b/arch/arm/mm/Kconfig
>> @@ -1029,7 +1029,7 @@ config ARM_L1_CACHE_SHIFT
>>  
>>  config ARM_DMA_MEM_BUFFERABLE
>>  	bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
>> -	default y if CPU_V6 || CPU_V6K || CPU_V7
>> +	default y if CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M
>>  	help
>>  	  Historically, the kernel has used strongly ordered mappings to
>>  	  provide DMA coherent memory.  With the advent of ARMv7, mapping
>>
> 
> 

[PATCH 3/7] drivers: dma-coherent: Account dma_pfn_offset when used with device tree

[Vladimir Murzin]

On 21/02/17 13:02, Vladimir Murzin wrote:
> On 21/02/17 12:37, Robin Murphy wrote:
>> On 15/02/17 09:59, Vladimir Murzin wrote:
>>> dma_declare_coherent_memory() and friends are designed to account
>>> difference in CPU and device addresses. However, when it is used with
>>> reserved memory regions there is assumption that CPU and device have
>>> the same view on address space. This assumption gets invalid when
>>> reserved memory for coherent DMA allocations is referenced by device
>>> with non-empty "dma-range" property.
>>>
>>> Simply feeding device address as rmem->base + dev->dma_pfn_offset
>>> would not work due to reserved memory region can be shared, so this
>>> patch turns device address to be expressed with help of CPU address
>>> and device's dma_pfn_offset.
>>>
>>> For the case where device tree is not used and device sees memory
>>> different to CPU we explicitly set device's dma_pfn_offset to
>>> accomplish such difference. The latter might look controversial, but
>>> it seems only a few drivers set device address different to CPU's:
>>> - drivers/usb/host/ohci-sm501.c
>>> - arch/sh/drivers/pci/fixups-dreamcast.c
>>> so they can be screwed only if dma_pfn_offset there is set and not in
>>> sync with device address range - we try to catch such cases with
>>> WARN_ON.
>>>
>>> Cc: Michal Nazarewicz <mina86@mina86.com>
>>> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
>>> Cc: Alan Stern <stern@rowland.harvard.edu>
>>> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
>>> Cc: Rich Felker <dalias@libc.org>
>>> Cc: Roger Quadros <rogerq@ti.com>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
>>> Tested-by: Andras Szemzo <sza@esh.hu>
>>> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
>>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
>>> ---
>>>  drivers/base/dma-coherent.c | 17 +++++++++++++++--
>>>  1 file changed, 15 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
>>> index 640a7e6..c59708c 100644
>>> --- a/drivers/base/dma-coherent.c
>>> +++ b/drivers/base/dma-coherent.c
>>> @@ -18,6 +18,12 @@ struct dma_coherent_mem {
>>>  	spinlock_t	spinlock;
>>>  };
>>>  
>>> +static inline dma_addr_t dma_get_device_base(struct device *dev,
>>> +					     struct dma_coherent_mem * mem)
>>> +{
>>> +	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
>>> +}
>>> +
>>>  static bool dma_init_coherent_memory(
>>>  	phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags,
>>>  	struct dma_coherent_mem **mem)
>>> @@ -83,9 +89,16 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
>>>  static int dma_assign_coherent_memory(struct device *dev,
>>>  				      struct dma_coherent_mem *mem)
>>>  {
>>> +	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
>>> +
>>>  	if (dev->dma_mem)
>>>  		return -EBUSY;
>>>  
>>> +	if (dev->dma_pfn_offset)
>>> +		WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset != dma_pfn_offset));
>>> +	else
>>> +		dev->dma_pfn_offset = dma_pfn_offset;
>>
>> This makes me rather uneasy - I can well imagine a device sharing the
>> CPU physical address map of external system memory, but having its own
>> view of its local coherent memory such that pfn_base != device_base
>> still. I know for a fact we've had internal FPGA tiles set up that way,
>> although whether it was entirely intentional is another matter... ;)
>>
>> In that situation, setting dev->dma_pfn_offset like this would break
>> streaming DMA for such devices. Could we not keep the pool-specific
>> offset and the device-specific offset independent, apply whichever is
>> non-zero, and scream if both are set?
> 
> Something like fixup bellow?
> 
> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
> index 0c577ea..2060010 100644
> --- a/drivers/base/dma-coherent.c
> +++ b/drivers/base/dma-coherent.c
> @@ -30,7 +30,15 @@ static inline struct dma_coherent_mem *dev_get_coherent_memory(struct device *de
>  static inline dma_addr_t dma_get_device_base(struct device *dev,
>  					     struct dma_coherent_mem * mem)
>  {
> -	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
> +	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
> +
> +	if (dma_pfn_offset != dev->dma_pfn_offset )
> +		WARN_ON(device_pfn_offset && dev->dma_pfn_offset);
                        ^^^^^^^^^^^^^^^^^
	       should be dma_pfn_offset

> +
> +	if (dma_pfn_offset)
> +		return mem->device_base;
> +	else
> +		return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
>  }
>  
>  static bool dma_init_coherent_memory(
> @@ -98,19 +106,12 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
>  static int dma_assign_coherent_memory(struct device *dev,
>  				      struct dma_coherent_mem *mem)
>  {
> -	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
> -
>  	if (!dev)
>  		return -ENODEV;
>  
>  	if (dev->dma_mem)
>  		return -EBUSY;
>  
> -	if (dev->dma_pfn_offset)
> -		WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset != dma_pfn_offset));
> -	else
> -		dev->dma_pfn_offset = dma_pfn_offset;
> -
>  	dev->dma_mem = mem;
>  	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
> 
> 
> Cheers
> Vladimir
> 
>>
>> Robin.
>>
>>> +
>>>  	dev->dma_mem = mem;
>>>  	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
>>>  
>>> @@ -133,7 +146,7 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
>>>  		return ERR_PTR(-EINVAL);
>>>  
>>>  	spin_lock_irqsave(&mem->spinlock, flags);
>>> -	pos = (device_addr - mem->device_base) >> PAGE_SHIFT;
>>> +	pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
>>>  	err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
>>>  	spin_unlock_irqrestore(&mem->spinlock, flags);
>>>  
>>> @@ -186,7 +199,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
>>>  	/*
>>>  	 * Memory was found in the per-device area.
>>>  	 */
>>> -	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
>>> +	*dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
>>>  	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
>>>  	dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
>>>  	spin_unlock_irqrestore(&mem->spinlock, flags);
>>>
>>
>>
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

[PATCH 1/7] dma: Take into account dma_pfn_offset

[Robin Murphy]

On 15/02/17 09:59, Vladimir Murzin wrote:
> Even though dma-noop-ops assumes 1:1 memory mapping DMA memory range
> can be different to RAM. For example, ARM STM32F4 MCU offers the
> possibility to remap SDRAM from 0xc000_0000 to 0x0 to get CPU
> performance boost, but DMA continue to see SDRAM at 0xc000_0000. This
> difference in mapping is handled via device-tree "dma-range" property
> which leads to dev->dma_pfn_offset is set nonzero. To handle such
> cases take dma_pfn_offset into account.

Modulo trivial style nits (include order, line length) which I'll leave
for others to object to if they wish, this looks correct to me.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Cc: Joerg Roedel <jroedel@suse.de>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Reported-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Tested-by: Andras Szemzo <sza@esh.hu>
> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> ---
>  lib/dma-noop.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/dma-noop.c b/lib/dma-noop.c
> index 3d766e7..a14eee5 100644
> --- a/lib/dma-noop.c
> +++ b/lib/dma-noop.c
> @@ -7,6 +7,7 @@
>  #include <linux/mm.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/scatterlist.h>
> +#include <linux/pfn.h>
>  
>  static void *dma_noop_alloc(struct device *dev, size_t size,
>  			    dma_addr_t *dma_handle, gfp_t gfp,
> @@ -16,7 +17,8 @@ static void *dma_noop_alloc(struct device *dev, size_t size,
>  
>  	ret = (void *)__get_free_pages(gfp, get_order(size));
>  	if (ret)
> -		*dma_handle = virt_to_phys(ret);
> +		*dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);
> +
>  	return ret;
>  }
>  
> @@ -32,7 +34,7 @@ static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
>  				      enum dma_data_direction dir,
>  				      unsigned long attrs)
>  {
> -	return page_to_phys(page) + offset;
> +	return page_to_phys(page) + offset - PFN_PHYS(dev->dma_pfn_offset);
>  }
>  
>  static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
> @@ -47,7 +49,7 @@ static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nent
>  
>  		BUG_ON(!sg_page(sg));
>  		va = sg_virt(sg);
> -		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
> +		sg_dma_address(sg) = (dma_addr_t)(virt_to_phys(va) - PFN_PHYS(dev->dma_pfn_offset));
>  		sg_dma_len(sg) = sg->length;
>  	}
>  
> 

[PATCH 1/7] dma: Take into account dma_pfn_offset

[Vladimir Murzin]

On 21/02/17 13:07, Robin Murphy wrote:
> On 15/02/17 09:59, Vladimir Murzin wrote:
>> Even though dma-noop-ops assumes 1:1 memory mapping DMA memory range
>> can be different to RAM. For example, ARM STM32F4 MCU offers the
>> possibility to remap SDRAM from 0xc000_0000 to 0x0 to get CPU
>> performance boost, but DMA continue to see SDRAM at 0xc000_0000. This
>> difference in mapping is handled via device-tree "dma-range" property
>> which leads to dev->dma_pfn_offset is set nonzero. To handle such
>> cases take dma_pfn_offset into account.
> 
> Modulo trivial style nits (include order, line length) which I'll leave
> for others to object to if they wish, this looks correct to me.
> 
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>

Much appreciated!

Vladimir

> 
>> Cc: Joerg Roedel <jroedel@suse.de>
>> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
>> Reported-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
>> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
>> Tested-by: Andras Szemzo <sza@esh.hu>
>> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
>> ---
>>  lib/dma-noop.c | 8 +++++---
>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/lib/dma-noop.c b/lib/dma-noop.c
>> index 3d766e7..a14eee5 100644
>> --- a/lib/dma-noop.c
>> +++ b/lib/dma-noop.c
>> @@ -7,6 +7,7 @@
>>  #include <linux/mm.h>
>>  #include <linux/dma-mapping.h>
>>  #include <linux/scatterlist.h>
>> +#include <linux/pfn.h>
>>  
>>  static void *dma_noop_alloc(struct device *dev, size_t size,
>>  			    dma_addr_t *dma_handle, gfp_t gfp,
>> @@ -16,7 +17,8 @@ static void *dma_noop_alloc(struct device *dev, size_t size,
>>  
>>  	ret = (void *)__get_free_pages(gfp, get_order(size));
>>  	if (ret)
>> -		*dma_handle = virt_to_phys(ret);
>> +		*dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);
>> +
>>  	return ret;
>>  }
>>  
>> @@ -32,7 +34,7 @@ static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
>>  				      enum dma_data_direction dir,
>>  				      unsigned long attrs)
>>  {
>> -	return page_to_phys(page) + offset;
>> +	return page_to_phys(page) + offset - PFN_PHYS(dev->dma_pfn_offset);
>>  }
>>  
>>  static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
>> @@ -47,7 +49,7 @@ static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nent
>>  
>>  		BUG_ON(!sg_page(sg));
>>  		va = sg_virt(sg);
>> -		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
>> +		sg_dma_address(sg) = (dma_addr_t)(virt_to_phys(va) - PFN_PHYS(dev->dma_pfn_offset));
>>  		sg_dma_len(sg) = sg->length;
>>  	}
>>  
>>
> 
> 

[PATCH 3/7] drivers: dma-coherent: Account dma_pfn_offset when used with device tree

[Robin Murphy]

On 21/02/17 13:02, Vladimir Murzin wrote:
> On 21/02/17 12:37, Robin Murphy wrote:
>> On 15/02/17 09:59, Vladimir Murzin wrote:
>>> dma_declare_coherent_memory() and friends are designed to account
>>> difference in CPU and device addresses. However, when it is used with
>>> reserved memory regions there is assumption that CPU and device have
>>> the same view on address space. This assumption gets invalid when
>>> reserved memory for coherent DMA allocations is referenced by device
>>> with non-empty "dma-range" property.
>>>
>>> Simply feeding device address as rmem->base + dev->dma_pfn_offset
>>> would not work due to reserved memory region can be shared, so this
>>> patch turns device address to be expressed with help of CPU address
>>> and device's dma_pfn_offset.
>>>
>>> For the case where device tree is not used and device sees memory
>>> different to CPU we explicitly set device's dma_pfn_offset to
>>> accomplish such difference. The latter might look controversial, but
>>> it seems only a few drivers set device address different to CPU's:
>>> - drivers/usb/host/ohci-sm501.c
>>> - arch/sh/drivers/pci/fixups-dreamcast.c
>>> so they can be screwed only if dma_pfn_offset there is set and not in
>>> sync with device address range - we try to catch such cases with
>>> WARN_ON.
>>>
>>> Cc: Michal Nazarewicz <mina86@mina86.com>
>>> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
>>> Cc: Alan Stern <stern@rowland.harvard.edu>
>>> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
>>> Cc: Rich Felker <dalias@libc.org>
>>> Cc: Roger Quadros <rogerq@ti.com>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
>>> Tested-by: Andras Szemzo <sza@esh.hu>
>>> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
>>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
>>> ---
>>>  drivers/base/dma-coherent.c | 17 +++++++++++++++--
>>>  1 file changed, 15 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
>>> index 640a7e6..c59708c 100644
>>> --- a/drivers/base/dma-coherent.c
>>> +++ b/drivers/base/dma-coherent.c
>>> @@ -18,6 +18,12 @@ struct dma_coherent_mem {
>>>  	spinlock_t	spinlock;
>>>  };
>>>  
>>> +static inline dma_addr_t dma_get_device_base(struct device *dev,
>>> +					     struct dma_coherent_mem * mem)
>>> +{
>>> +	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
>>> +}
>>> +
>>>  static bool dma_init_coherent_memory(
>>>  	phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags,
>>>  	struct dma_coherent_mem **mem)
>>> @@ -83,9 +89,16 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
>>>  static int dma_assign_coherent_memory(struct device *dev,
>>>  				      struct dma_coherent_mem *mem)
>>>  {
>>> +	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
>>> +
>>>  	if (dev->dma_mem)
>>>  		return -EBUSY;
>>>  
>>> +	if (dev->dma_pfn_offset)
>>> +		WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset != dma_pfn_offset));
>>> +	else
>>> +		dev->dma_pfn_offset = dma_pfn_offset;
>>
>> This makes me rather uneasy - I can well imagine a device sharing the
>> CPU physical address map of external system memory, but having its own
>> view of its local coherent memory such that pfn_base != device_base
>> still. I know for a fact we've had internal FPGA tiles set up that way,
>> although whether it was entirely intentional is another matter... ;)
>>
>> In that situation, setting dev->dma_pfn_offset like this would break
>> streaming DMA for such devices. Could we not keep the pool-specific
>> offset and the device-specific offset independent, apply whichever is
>> non-zero, and scream if both are set?
> 
> Something like fixup bellow?
> 
> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
> index 0c577ea..2060010 100644
> --- a/drivers/base/dma-coherent.c
> +++ b/drivers/base/dma-coherent.c
> @@ -30,7 +30,15 @@ static inline struct dma_coherent_mem *dev_get_coherent_memory(struct device *de
>  static inline dma_addr_t dma_get_device_base(struct device *dev,
>  					     struct dma_coherent_mem * mem)
>  {
> -	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
> +	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
> +
> +	if (dma_pfn_offset != dev->dma_pfn_offset )
> +		WARN_ON(device_pfn_offset && dev->dma_pfn_offset);
> +
> +	if (dma_pfn_offset)
> +		return mem->device_base;
> +	else
> +		return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
>  }

More or less - I can't resist the temptation to golf it down a bit
though, do you reckon this scores any higher for readability?

	unsigned long dev_pfn = PFN_DOWN(mem->device_base);

	if (dev_pfn == mem->pfn_base)
		dev_pfn -= dev->dma_pfn_offset;
	else
		WARN_ON(dev->dma_pfn_offset);

	return (dma_addr_t)dev_pfn << PAGE_SHIFT;

perhaps with a comment that it's not entirely unambiguous what it would
mean for both offsets to be nonzero (even if they were equal), so we'd
need to revisit the whole thing anyway in the vanishingly unlikely
situation that any hardware that crazy ever appears.

Another possibility is that we add something in mem->flags to indicate
if it came from of_reserved_mem, and only apply dev->dma_pfn_offset in
those cases. That feels like it might actually be a bit more robust.

Robin.

>  static bool dma_init_coherent_memory(
> @@ -98,19 +106,12 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
>  static int dma_assign_coherent_memory(struct device *dev,
>  				      struct dma_coherent_mem *mem)
>  {
> -	unsigned long dma_pfn_offset = mem->pfn_base - PFN_DOWN(mem->device_base);
> -
>  	if (!dev)
>  		return -ENODEV;
>  
>  	if (dev->dma_mem)
>  		return -EBUSY;
>  
> -	if (dev->dma_pfn_offset)
> -		WARN_ON(dma_pfn_offset && (dev->dma_pfn_offset != dma_pfn_offset));
> -	else
> -		dev->dma_pfn_offset = dma_pfn_offset;
> -
>  	dev->dma_mem = mem;
>  	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
> 
> 
> Cheers
> Vladimir
> 
>>
>> Robin.
>>
>>> +
>>>  	dev->dma_mem = mem;
>>>  	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
>>>  
>>> @@ -133,7 +146,7 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
>>>  		return ERR_PTR(-EINVAL);
>>>  
>>>  	spin_lock_irqsave(&mem->spinlock, flags);
>>> -	pos = (device_addr - mem->device_base) >> PAGE_SHIFT;
>>> +	pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
>>>  	err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
>>>  	spin_unlock_irqrestore(&mem->spinlock, flags);
>>>  
>>> @@ -186,7 +199,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
>>>  	/*
>>>  	 * Memory was found in the per-device area.
>>>  	 */
>>> -	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
>>> +	*dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
>>>  	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
>>>  	dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
>>>  	spin_unlock_irqrestore(&mem->spinlock, flags);
>>>
>>
>>
>