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* remove default fallbacks in dma_map_ops v2
@ 2019-08-05  9:11 Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 1/7] dma-mapping: move the dma_get_sgtable API comments from arm to common code Christoph Hellwig
                   ` (6 more replies)
  0 siblings, 7 replies; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-05  9:11 UTC (permalink / raw)
  To: iommu, Marek Szyprowski
  Cc: Takashi Iwai, Robin Murphy, Michal Simek, linux-arm-kernel,
	linux-m68k, linux-parisc, linux-sh, linux-xtensa, linuxppc-dev,
	x86, linux-kernel

Hi all,

we have a few places where the DMA mapping layer has non-trivial default
actions that are questionable and/or dangerous.

This series instead wires up the mmap, get_sgtable and get_required_mask
methods explicitly and cleans up some surrounding areas.  This also means
we could get rid of the ARCH_NO_COHERENT_DMA_MMAP kconfig option, as we
now require a mmap method wired up, or in case of non-coherent dma-direct
the presence of the arch_dma_coherent_to_pfn hook.  The only interesting
case is that the sound code also checked the ARCH_NO_COHERENT_DMA_MMAP
symbol in somewhat odd ways, so I'd like to see a review of the sound
situation before going forward with that patch.

Changes since v1:
 - add a dma_can_mmap helper for alsa

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 1/7] dma-mapping: move the dma_get_sgtable API comments from arm to common code
  2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
@ 2019-08-05  9:11 ` Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 2/7] dma-mapping: explicitly wire up ->mmap and ->get_sgtable Christoph Hellwig
                   ` (5 subsequent siblings)
  6 siblings, 0 replies; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-05  9:11 UTC (permalink / raw)
  To: iommu, Marek Szyprowski
  Cc: Takashi Iwai, Robin Murphy, Michal Simek, linux-arm-kernel,
	linux-m68k, linux-parisc, linux-sh, linux-xtensa, linuxppc-dev,
	x86, linux-kernel

The comments are spot on and should be near the central API, not just
near a single implementation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm/mm/dma-mapping.c | 11 -----------
 kernel/dma/mapping.c      | 11 +++++++++++
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 6774b03aa405..4410af33c5c4 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -877,17 +877,6 @@ static void arm_coherent_dma_free(struct device *dev, size_t size, void *cpu_add
 	__arm_dma_free(dev, size, cpu_addr, handle, attrs, true);
 }
 
-/*
- * The whole dma_get_sgtable() idea is fundamentally unsafe - it seems
- * that the intention is to allow exporting memory allocated via the
- * coherent DMA APIs through the dma_buf API, which only accepts a
- * scattertable.  This presents a couple of problems:
- * 1. Not all memory allocated via the coherent DMA APIs is backed by
- *    a struct page
- * 2. Passing coherent DMA memory into the streaming APIs is not allowed
- *    as we will try to flush the memory through a different alias to that
- *    actually being used (and the flushes are redundant.)
- */
 int arm_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
 		 void *cpu_addr, dma_addr_t handle, size_t size,
 		 unsigned long attrs)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index b945239621d8..4ceb5b9016d8 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -136,6 +136,17 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
 	return ret;
 }
 
+/*
+ * The whole dma_get_sgtable() idea is fundamentally unsafe - it seems
+ * that the intention is to allow exporting memory allocated via the
+ * coherent DMA APIs through the dma_buf API, which only accepts a
+ * scattertable.  This presents a couple of problems:
+ * 1. Not all memory allocated via the coherent DMA APIs is backed by
+ *    a struct page
+ * 2. Passing coherent DMA memory into the streaming APIs is not allowed
+ *    as we will try to flush the memory through a different alias to that
+ *    actually being used (and the flushes are redundant.)
+ */
 int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		unsigned long attrs)
-- 
2.20.1


^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 2/7] dma-mapping: explicitly wire up ->mmap and ->get_sgtable
  2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 1/7] dma-mapping: move the dma_get_sgtable API comments from arm to common code Christoph Hellwig
@ 2019-08-05  9:11 ` Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 3/7] dma-mapping: add a dma_can_mmap helper Christoph Hellwig
                   ` (4 subsequent siblings)
  6 siblings, 0 replies; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-05  9:11 UTC (permalink / raw)
  To: iommu, Marek Szyprowski
  Cc: Takashi Iwai, Robin Murphy, Michal Simek, linux-arm-kernel,
	linux-m68k, linux-parisc, linux-sh, linux-xtensa, linuxppc-dev,
	x86, linux-kernel

While the default ->mmap and ->get_sgtable implementations work for the
majority of our dma_map_ops impementations they are inherently safe
for others that don't use the page allocator or CMA and/or use their
own way of remapping not covered by the common code.  So remove the
defaults if these methods are not wired up, but instead wire up the
default implementations for all safe instances.

Fixes: e1c7e324539a ("dma-mapping: always provide the dma_map_ops based implementation")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/alpha/kernel/pci_iommu.c           |  2 ++
 arch/ia64/hp/common/sba_iommu.c         |  2 ++
 arch/ia64/sn/pci/pci_dma.c              |  2 ++
 arch/mips/jazz/jazzdma.c                |  2 ++
 arch/powerpc/kernel/dma-iommu.c         |  2 ++
 arch/powerpc/platforms/ps3/system-bus.c |  4 ++++
 arch/powerpc/platforms/pseries/vio.c    |  2 ++
 arch/s390/pci/pci_dma.c                 |  2 ++
 arch/x86/kernel/amd_gart_64.c           |  2 ++
 arch/x86/kernel/pci-calgary_64.c        |  2 ++
 drivers/iommu/amd_iommu.c               |  2 ++
 drivers/iommu/intel-iommu.c             |  2 ++
 kernel/dma/mapping.c                    | 20 ++++++++++++--------
 13 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.c
index 242108439f42..7f1925a32c99 100644
--- a/arch/alpha/kernel/pci_iommu.c
+++ b/arch/alpha/kernel/pci_iommu.c
@@ -955,5 +955,7 @@ const struct dma_map_ops alpha_pci_ops = {
 	.map_sg			= alpha_pci_map_sg,
 	.unmap_sg		= alpha_pci_unmap_sg,
 	.dma_supported		= alpha_pci_supported,
+	.mmap			= dma_common_mmap,
+	.get_sgtable		= dma_common_get_sgtable,
 };
 EXPORT_SYMBOL(alpha_pci_ops);
diff --git a/arch/ia64/hp/common/sba_iommu.c b/arch/ia64/hp/common/sba_iommu.c
index 3d24cc43385b..4c0ea6c2833d 100644
--- a/arch/ia64/hp/common/sba_iommu.c
+++ b/arch/ia64/hp/common/sba_iommu.c
@@ -2183,6 +2183,8 @@ const struct dma_map_ops sba_dma_ops = {
 	.map_sg			= sba_map_sg_attrs,
 	.unmap_sg		= sba_unmap_sg_attrs,
 	.dma_supported		= sba_dma_supported,
+	.mmap			= dma_common_mmap,
+	.get_sgtable		= dma_common_get_sgtable,
 };
 
 void sba_dma_init(void)
diff --git a/arch/ia64/sn/pci/pci_dma.c b/arch/ia64/sn/pci/pci_dma.c
index b7d42e4edc1f..12ffb9c0d738 100644
--- a/arch/ia64/sn/pci/pci_dma.c
+++ b/arch/ia64/sn/pci/pci_dma.c
@@ -438,6 +438,8 @@ static struct dma_map_ops sn_dma_ops = {
 	.unmap_sg		= sn_dma_unmap_sg,
 	.dma_supported		= sn_dma_supported,
 	.get_required_mask	= sn_dma_get_required_mask,
+	.mmap			= dma_common_mmap,
+	.get_sgtable		= dma_common_get_sgtable,
 };
 
 void sn_dma_init(void)
diff --git a/arch/mips/jazz/jazzdma.c b/arch/mips/jazz/jazzdma.c
index 1804dc9d8136..a01e14955187 100644
--- a/arch/mips/jazz/jazzdma.c
+++ b/arch/mips/jazz/jazzdma.c
@@ -682,5 +682,7 @@ const struct dma_map_ops jazz_dma_ops = {
 	.sync_sg_for_device	= jazz_dma_sync_sg_for_device,
 	.dma_supported		= dma_direct_supported,
 	.cache_sync		= arch_dma_cache_sync,
+	.mmap			= dma_common_mmap,
+	.get_sgtable		= dma_common_get_sgtable,
 };
 EXPORT_SYMBOL(jazz_dma_ops);
diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c
index a0879674a9c8..2f5a53874f6d 100644
--- a/arch/powerpc/kernel/dma-iommu.c
+++ b/arch/powerpc/kernel/dma-iommu.c
@@ -208,4 +208,6 @@ const struct dma_map_ops dma_iommu_ops = {
 	.sync_single_for_device	= dma_iommu_sync_for_device,
 	.sync_sg_for_cpu	= dma_iommu_sync_sg_for_cpu,
 	.sync_sg_for_device	= dma_iommu_sync_sg_for_device,
+	.mmap			= dma_common_mmap,
+	.get_sgtable		= dma_common_get_sgtable,
 };
diff --git a/arch/powerpc/platforms/ps3/system-bus.c b/arch/powerpc/platforms/ps3/system-bus.c
index 98410119c47b..70fcc9736a8c 100644
--- a/arch/powerpc/platforms/ps3/system-bus.c
+++ b/arch/powerpc/platforms/ps3/system-bus.c
@@ -700,6 +700,8 @@ static const struct dma_map_ops ps3_sb_dma_ops = {
 	.get_required_mask = ps3_dma_get_required_mask,
 	.map_page = ps3_sb_map_page,
 	.unmap_page = ps3_unmap_page,
+	.mmap = dma_common_mmap,
+	.get_sgtable = dma_common_get_sgtable,
 };
 
 static const struct dma_map_ops ps3_ioc0_dma_ops = {
@@ -711,6 +713,8 @@ static const struct dma_map_ops ps3_ioc0_dma_ops = {
 	.get_required_mask = ps3_dma_get_required_mask,
 	.map_page = ps3_ioc0_map_page,
 	.unmap_page = ps3_unmap_page,
+	.mmap = dma_common_mmap,
+	.get_sgtable = dma_common_get_sgtable,
 };
 
 /**
diff --git a/arch/powerpc/platforms/pseries/vio.c b/arch/powerpc/platforms/pseries/vio.c
index 6601b9d404dc..3473eef7628c 100644
--- a/arch/powerpc/platforms/pseries/vio.c
+++ b/arch/powerpc/platforms/pseries/vio.c
@@ -605,6 +605,8 @@ static const struct dma_map_ops vio_dma_mapping_ops = {
 	.unmap_page        = vio_dma_iommu_unmap_page,
 	.dma_supported     = dma_iommu_dma_supported,
 	.get_required_mask = dma_iommu_get_required_mask,
+	.mmap		   = dma_common_mmap,
+	.get_sgtable	   = dma_common_get_sgtable,
 };
 
 /**
diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
index 9e52d1527f71..03d8c1c9f82f 100644
--- a/arch/s390/pci/pci_dma.c
+++ b/arch/s390/pci/pci_dma.c
@@ -668,6 +668,8 @@ const struct dma_map_ops s390_pci_dma_ops = {
 	.unmap_sg	= s390_dma_unmap_sg,
 	.map_page	= s390_dma_map_pages,
 	.unmap_page	= s390_dma_unmap_pages,
+	.mmap		= dma_common_mmap,
+	.get_sgtable	= dma_common_get_sgtable,
 	/* dma_supported is unconditionally true without a callback */
 };
 EXPORT_SYMBOL_GPL(s390_pci_dma_ops);
diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
index a585ea6f686a..a65b4a9c7f87 100644
--- a/arch/x86/kernel/amd_gart_64.c
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -678,6 +678,8 @@ static const struct dma_map_ops gart_dma_ops = {
 	.alloc				= gart_alloc_coherent,
 	.free				= gart_free_coherent,
 	.dma_supported			= dma_direct_supported,
+	.mmap				= dma_common_mmap,
+	.get_sgtable			= dma_common_get_sgtable,
 };
 
 static void gart_iommu_shutdown(void)
diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
index 9d4343aa481b..23fdec030c37 100644
--- a/arch/x86/kernel/pci-calgary_64.c
+++ b/arch/x86/kernel/pci-calgary_64.c
@@ -468,6 +468,8 @@ static const struct dma_map_ops calgary_dma_ops = {
 	.map_page = calgary_map_page,
 	.unmap_page = calgary_unmap_page,
 	.dma_supported = dma_direct_supported,
+	.mmap = dma_common_mmap,
+	.get_sgtable = dma_common_get_sgtable,
 };
 
 static inline void __iomem * busno_to_bbar(unsigned char num)
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index b607a92791d3..2e74ad659985 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2722,6 +2722,8 @@ static const struct dma_map_ops amd_iommu_dma_ops = {
 	.map_sg		= map_sg,
 	.unmap_sg	= unmap_sg,
 	.dma_supported	= amd_iommu_dma_supported,
+	.mmap		= dma_common_mmap,
+	.get_sgtable	= dma_common_get_sgtable,
 };
 
 static int init_reserved_iova_ranges(void)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index bdaed2da8a55..7505c5d9cf78 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3737,6 +3737,8 @@ static const struct dma_map_ops intel_dma_ops = {
 	.map_resource = intel_map_resource,
 	.unmap_resource = intel_unmap_resource,
 	.dma_supported = dma_direct_supported,
+	.mmap = dma_common_mmap,
+	.get_sgtable = dma_common_get_sgtable,
 };
 
 static inline int iommu_domain_cache_init(void)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 4ceb5b9016d8..cdb157cd70e7 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -153,11 +153,12 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (!dma_is_direct(ops) && ops->get_sgtable)
-		return ops->get_sgtable(dev, sgt, cpu_addr, dma_addr, size,
-					attrs);
-	return dma_common_get_sgtable(dev, sgt, cpu_addr, dma_addr, size,
-			attrs);
+	if (dma_is_direct(ops))
+		return dma_common_get_sgtable(dev, sgt, cpu_addr, dma_addr,
+				size, attrs);
+	if (!ops->get_sgtable)
+		return -ENXIO;
+	return ops->get_sgtable(dev, sgt, cpu_addr, dma_addr, size, attrs);
 }
 EXPORT_SYMBOL(dma_get_sgtable_attrs);
 
@@ -221,9 +222,12 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (!dma_is_direct(ops) && ops->mmap)
-		return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
-	return dma_common_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
+	if (dma_is_direct(ops))
+		return dma_common_mmap(dev, vma, cpu_addr, dma_addr, size,
+				attrs);
+	if (!ops->mmap)
+		return -ENXIO;
+	return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
 }
 EXPORT_SYMBOL(dma_mmap_attrs);
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 3/7] dma-mapping: add a dma_can_mmap helper
  2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 1/7] dma-mapping: move the dma_get_sgtable API comments from arm to common code Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 2/7] dma-mapping: explicitly wire up ->mmap and ->get_sgtable Christoph Hellwig
@ 2019-08-05  9:11 ` Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_* Christoph Hellwig
                   ` (3 subsequent siblings)
  6 siblings, 0 replies; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-05  9:11 UTC (permalink / raw)
  To: iommu, Marek Szyprowski
  Cc: Takashi Iwai, Robin Murphy, Michal Simek, linux-arm-kernel,
	linux-m68k, linux-parisc, linux-sh, linux-xtensa, linuxppc-dev,
	x86, linux-kernel

Add a helper to check if DMA allocations for a specific device can be
mapped to userspace using dma_mmap_*.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/dma-mapping.h |  5 +++++
 kernel/dma/mapping.c        | 23 +++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f7d1eea32c78..17271857be5d 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -462,6 +462,7 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
 int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		unsigned long attrs);
+bool dma_can_mmap(struct device *dev);
 int dma_supported(struct device *dev, u64 mask);
 int dma_set_mask(struct device *dev, u64 mask);
 int dma_set_coherent_mask(struct device *dev, u64 mask);
@@ -552,6 +553,10 @@ static inline int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 {
 	return -ENXIO;
 }
+static inline bool dma_can_mmap(struct device *dev)
+{
+	return false;
+}
 static inline int dma_supported(struct device *dev, u64 mask)
 {
 	return 0;
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index cdb157cd70e7..ab6aa355e1a0 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -203,6 +203,29 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 #endif /* !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */
 }
 
+/**
+ * dma_can_mmap - check if a given device supports dma_mmap_*
+ * @dev: device to check
+ *
+ * Returns %true if @dev supports dma_mmap_coherent() and dma_mmap_attrs() to
+ * map DMA allocations to userspace.
+ */
+bool dma_can_mmap(struct device *dev)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	if (IS_ENABLED(CONFIG_ARCH_NO_COHERENT_DMA_MMAP))
+		return false;
+
+	if (dma_is_direct(ops)) {
+		return dev_is_dma_coherent(dev) ||
+			IS_ENABLED(CONFIG_ARCH_HAS_DMA_COHERENT_TO_PFN);
+	}
+
+	return ops->mmap != NULL;
+}
+EXPORT_SYMBOL_GPL(dma_can_mmap);
+
 /**
  * dma_mmap_attrs - map a coherent DMA allocation into user space
  * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
-- 
2.20.1


^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_*
  2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
                   ` (2 preceding siblings ...)
  2019-08-05  9:11 ` [PATCH 3/7] dma-mapping: add a dma_can_mmap helper Christoph Hellwig
@ 2019-08-05  9:11 ` Christoph Hellwig
  2019-08-05  9:22   ` Takashi Iwai
  2019-08-05  9:11 ` [PATCH 5/7] m68knommu: add a pgprot_noncached stub Christoph Hellwig
                   ` (2 subsequent siblings)
  6 siblings, 1 reply; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-05  9:11 UTC (permalink / raw)
  To: iommu, Marek Szyprowski
  Cc: Takashi Iwai, Robin Murphy, Michal Simek, linux-arm-kernel,
	linux-m68k, linux-parisc, linux-sh, linux-xtensa, linuxppc-dev,
	x86, linux-kernel

Replace the local hack with the dma_can_mmap helper to check if
a given device supports mapping DMA allocations to userspace.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 sound/core/pcm_native.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 703857aab00f..81c82c3ee8a2 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -220,12 +220,11 @@ static bool hw_support_mmap(struct snd_pcm_substream *substream)
 {
 	if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_MMAP))
 		return false;
-	/* architecture supports dma_mmap_coherent()? */
-#if defined(CONFIG_ARCH_NO_COHERENT_DMA_MMAP) || !defined(CONFIG_HAS_DMA)
+	if (!dma_can_mmap(substream->dma_buffer.dev.dev))
+		return false;
 	if (!substream->ops->mmap &&
 	    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
 		return false;
-#endif
 	return true;
 }
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 5/7] m68knommu: add a pgprot_noncached stub
  2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
                   ` (3 preceding siblings ...)
  2019-08-05  9:11 ` [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_* Christoph Hellwig
@ 2019-08-05  9:11 ` Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 6/7] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 7/7] dma-mapping: provide a better default ->get_required_mask Christoph Hellwig
  6 siblings, 0 replies; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-05  9:11 UTC (permalink / raw)
  To: iommu, Marek Szyprowski
  Cc: Takashi Iwai, Robin Murphy, Michal Simek, linux-arm-kernel,
	linux-m68k, linux-parisc, linux-sh, linux-xtensa, linuxppc-dev,
	x86, linux-kernel

Provide a pgprot_noncached like all the other nommu ports so that
common code can rely on it being able to be present.  Note that this is
generally code that is not actually run on nommu, but at least we can
avoid nasty ifdefs by having a stub.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/m68k/include/asm/pgtable_no.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/m68k/include/asm/pgtable_no.h b/arch/m68k/include/asm/pgtable_no.h
index fc3a96c77bd8..06194c7ba151 100644
--- a/arch/m68k/include/asm/pgtable_no.h
+++ b/arch/m68k/include/asm/pgtable_no.h
@@ -29,6 +29,8 @@
 #define PAGE_READONLY	__pgprot(0)
 #define PAGE_KERNEL	__pgprot(0)
 
+#define pgprot_noncached(prot)   (prot)
+
 extern void paging_init(void);
 #define swapper_pg_dir ((pgd_t *) 0)
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 6/7] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP
  2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
                   ` (4 preceding siblings ...)
  2019-08-05  9:11 ` [PATCH 5/7] m68knommu: add a pgprot_noncached stub Christoph Hellwig
@ 2019-08-05  9:11 ` Christoph Hellwig
  2019-08-05  9:11 ` [PATCH 7/7] dma-mapping: provide a better default ->get_required_mask Christoph Hellwig
  6 siblings, 0 replies; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-05  9:11 UTC (permalink / raw)
  To: iommu, Marek Szyprowski
  Cc: Takashi Iwai, Robin Murphy, Michal Simek, linux-arm-kernel,
	linux-m68k, linux-parisc, linux-sh, linux-xtensa, linuxppc-dev,
	x86, linux-kernel

Now that we never use a default ->mmap implementation, and non-coherent
architectures can control the presence of ->mmap support by enabling
ARCH_HAS_DMA_COHERENT_TO_PFN for the dma direct implementation there
is no need for a global config option to control the availability
of dma_common_mmap.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/Kconfig            | 3 ---
 arch/c6x/Kconfig        | 1 -
 arch/m68k/Kconfig       | 1 -
 arch/microblaze/Kconfig | 1 -
 arch/parisc/Kconfig     | 1 -
 arch/sh/Kconfig         | 1 -
 arch/xtensa/Kconfig     | 1 -
 kernel/dma/mapping.c    | 7 -------
 8 files changed, 16 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index a7b57dd42c26..ec2834206d08 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -790,9 +790,6 @@ config COMPAT_32BIT_TIME
 	  This is relevant on all 32-bit architectures, and 64-bit architectures
 	  as part of compat syscall handling.
 
-config ARCH_NO_COHERENT_DMA_MMAP
-	bool
-
 config ARCH_NO_PREEMPT
 	bool
 
diff --git a/arch/c6x/Kconfig b/arch/c6x/Kconfig
index b4fb61c83494..e65e8d82442a 100644
--- a/arch/c6x/Kconfig
+++ b/arch/c6x/Kconfig
@@ -20,7 +20,6 @@ config C6X
 	select OF_EARLY_FLATTREE
 	select GENERIC_CLOCKEVENTS
 	select MODULES_USE_ELF_RELA
-	select ARCH_NO_COHERENT_DMA_MMAP
 	select MMU_GATHER_NO_RANGE if MMU
 
 config MMU
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index c518d695c376..614b355ae338 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -8,7 +8,6 @@ config M68K
 	select ARCH_HAS_DMA_PREP_COHERENT if HAS_DMA && MMU && !COLDFIRE
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
 	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
-	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select ARCH_NO_PREEMPT if !COLDFIRE
 	select BINFMT_FLAT_ARGVP_ENVP_ON_STACK
 	select DMA_DIRECT_REMAP if HAS_DMA && MMU && !COLDFIRE
diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index d411de05b628..632c9477a0f6 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -9,7 +9,6 @@ config MICROBLAZE
 	select ARCH_HAS_SYNC_DMA_FOR_CPU
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
 	select ARCH_MIGHT_HAVE_PC_PARPORT
-	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_EXTABLE_SORT
 	select TIMER_OF
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 6d732e451071..e9dd88b7f81e 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -52,7 +52,6 @@ config PARISC
 	select GENERIC_SCHED_CLOCK
 	select HAVE_UNSTABLE_SCHED_CLOCK if SMP
 	select GENERIC_CLOCKEVENTS
-	select ARCH_NO_COHERENT_DMA_MMAP
 	select CPU_NO_EFFICIENT_FFS
 	select NEED_DMA_MAP_STATE
 	select NEED_SG_DMA_LENGTH
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 6b1b5941b618..f356ee674d89 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -5,7 +5,6 @@ config SUPERH
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_MIGHT_HAVE_PC_PARPORT
-	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select HAVE_PATA_PLATFORM
 	select CLKDEV_LOOKUP
 	select DMA_DECLARE_COHERENT
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index ebc135bda921..70653aed3005 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -5,7 +5,6 @@ config XTENSA
 	select ARCH_HAS_BINFMT_FLAT if !MMU
 	select ARCH_HAS_SYNC_DMA_FOR_CPU
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
-	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
 	select ARCH_WANT_FRAME_POINTERS
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index ab6aa355e1a0..47765c96fe09 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -169,7 +169,6 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		unsigned long attrs)
 {
-#ifndef CONFIG_ARCH_NO_COHERENT_DMA_MMAP
 	unsigned long user_count = vma_pages(vma);
 	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	unsigned long off = vma->vm_pgoff;
@@ -198,9 +197,6 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 
 	return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
 			user_count << PAGE_SHIFT, vma->vm_page_prot);
-#else
-	return -ENXIO;
-#endif /* !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */
 }
 
 /**
@@ -214,9 +210,6 @@ bool dma_can_mmap(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (IS_ENABLED(CONFIG_ARCH_NO_COHERENT_DMA_MMAP))
-		return false;
-
 	if (dma_is_direct(ops)) {
 		return dev_is_dma_coherent(dev) ||
 			IS_ENABLED(CONFIG_ARCH_HAS_DMA_COHERENT_TO_PFN);
-- 
2.20.1


^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH 7/7] dma-mapping: provide a better default ->get_required_mask
  2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
                   ` (5 preceding siblings ...)
  2019-08-05  9:11 ` [PATCH 6/7] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP Christoph Hellwig
@ 2019-08-05  9:11 ` Christoph Hellwig
  6 siblings, 0 replies; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-05  9:11 UTC (permalink / raw)
  To: iommu, Marek Szyprowski
  Cc: Takashi Iwai, Robin Murphy, Michal Simek, linux-arm-kernel,
	linux-m68k, linux-parisc, linux-sh, linux-xtensa, linuxppc-dev,
	x86, linux-kernel

Most dma_map_ops instances are IOMMUs that work perfectly fine in 32-bits
of IOVA space, and the generic direct mapping code already provides its
own routines that is intelligent based on the amount of memory actually
present.  Wire up the dma-direct routine for the ARM direct mapping code
as well, and otherwise default to the constant 32-bit mask.  This way
we only need to override it for the occasional odd IOMMU that requires
64-bit IOVA support, or IOMMU drivers that are more efficient if they
can fall back to the direct mapping.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm/mm/dma-mapping.c               |  3 +++
 arch/powerpc/platforms/ps3/system-bus.c |  7 ------
 arch/x86/kernel/amd_gart_64.c           |  1 +
 kernel/dma/mapping.c                    | 30 +++++++++----------------
 4 files changed, 14 insertions(+), 27 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 4410af33c5c4..9c9a23e5600d 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -14,6 +14,7 @@
 #include <linux/list.h>
 #include <linux/init.h>
 #include <linux/device.h>
+#include <linux/dma-direct.h>
 #include <linux/dma-mapping.h>
 #include <linux/dma-noncoherent.h>
 #include <linux/dma-contiguous.h>
@@ -192,6 +193,7 @@ const struct dma_map_ops arm_dma_ops = {
 	.sync_sg_for_cpu	= arm_dma_sync_sg_for_cpu,
 	.sync_sg_for_device	= arm_dma_sync_sg_for_device,
 	.dma_supported		= arm_dma_supported,
+	.get_required_mask	= dma_direct_get_required_mask,
 };
 EXPORT_SYMBOL(arm_dma_ops);
 
@@ -212,6 +214,7 @@ const struct dma_map_ops arm_coherent_dma_ops = {
 	.map_sg			= arm_dma_map_sg,
 	.map_resource		= dma_direct_map_resource,
 	.dma_supported		= arm_dma_supported,
+	.get_required_mask	= dma_direct_get_required_mask,
 };
 EXPORT_SYMBOL(arm_coherent_dma_ops);
 
diff --git a/arch/powerpc/platforms/ps3/system-bus.c b/arch/powerpc/platforms/ps3/system-bus.c
index 70fcc9736a8c..3542b7bd6a46 100644
--- a/arch/powerpc/platforms/ps3/system-bus.c
+++ b/arch/powerpc/platforms/ps3/system-bus.c
@@ -686,18 +686,12 @@ static int ps3_dma_supported(struct device *_dev, u64 mask)
 	return mask >= DMA_BIT_MASK(32);
 }
 
-static u64 ps3_dma_get_required_mask(struct device *_dev)
-{
-	return DMA_BIT_MASK(32);
-}
-
 static const struct dma_map_ops ps3_sb_dma_ops = {
 	.alloc = ps3_alloc_coherent,
 	.free = ps3_free_coherent,
 	.map_sg = ps3_sb_map_sg,
 	.unmap_sg = ps3_sb_unmap_sg,
 	.dma_supported = ps3_dma_supported,
-	.get_required_mask = ps3_dma_get_required_mask,
 	.map_page = ps3_sb_map_page,
 	.unmap_page = ps3_unmap_page,
 	.mmap = dma_common_mmap,
@@ -710,7 +704,6 @@ static const struct dma_map_ops ps3_ioc0_dma_ops = {
 	.map_sg = ps3_ioc0_map_sg,
 	.unmap_sg = ps3_ioc0_unmap_sg,
 	.dma_supported = ps3_dma_supported,
-	.get_required_mask = ps3_dma_get_required_mask,
 	.map_page = ps3_ioc0_map_page,
 	.unmap_page = ps3_unmap_page,
 	.mmap = dma_common_mmap,
diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
index a65b4a9c7f87..d02662238b57 100644
--- a/arch/x86/kernel/amd_gart_64.c
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -680,6 +680,7 @@ static const struct dma_map_ops gart_dma_ops = {
 	.dma_supported			= dma_direct_supported,
 	.mmap				= dma_common_mmap,
 	.get_sgtable			= dma_common_get_sgtable,
+	.get_required_mask		= dma_direct_get_required_mask,
 };
 
 static void gart_iommu_shutdown(void)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 47765c96fe09..96599f39f67a 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -247,25 +247,6 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 }
 EXPORT_SYMBOL(dma_mmap_attrs);
 
-static u64 dma_default_get_required_mask(struct device *dev)
-{
-	u32 low_totalram = ((max_pfn - 1) << PAGE_SHIFT);
-	u32 high_totalram = ((max_pfn - 1) >> (32 - PAGE_SHIFT));
-	u64 mask;
-
-	if (!high_totalram) {
-		/* convert to mask just covering totalram */
-		low_totalram = (1 << (fls(low_totalram) - 1));
-		low_totalram += low_totalram - 1;
-		mask = low_totalram;
-	} else {
-		high_totalram = (1 << (fls(high_totalram) - 1));
-		high_totalram += high_totalram - 1;
-		mask = (((u64)high_totalram) << 32) + 0xffffffff;
-	}
-	return mask;
-}
-
 u64 dma_get_required_mask(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -274,7 +255,16 @@ u64 dma_get_required_mask(struct device *dev)
 		return dma_direct_get_required_mask(dev);
 	if (ops->get_required_mask)
 		return ops->get_required_mask(dev);
-	return dma_default_get_required_mask(dev);
+
+	/*
+	 * We require every DMA ops implementation to at least support a 32-bit
+	 * DMA mask (and use bounce buffering if that isn't supported in
+	 * hardware).  As the direct mapping code has its own routine to
+	 * actually report an optimal mask we default to 32-bit here as that
+	 * is the right thing for most IOMMUs, and at least not actively
+	 * harmful in general.
+	 */
+	return DMA_BIT_MASK(32);
 }
 EXPORT_SYMBOL_GPL(dma_get_required_mask);
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_*
  2019-08-05  9:11 ` [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_* Christoph Hellwig
@ 2019-08-05  9:22   ` Takashi Iwai
  2019-08-06  5:29     ` Christoph Hellwig
  0 siblings, 1 reply; 11+ messages in thread
From: Takashi Iwai @ 2019-08-05  9:22 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: iommu, Marek Szyprowski, Takashi Iwai, Robin Murphy,
	Michal Simek, linux-arm-kernel, linux-m68k, linux-parisc,
	linux-sh, linux-xtensa, linuxppc-dev, x86, linux-kernel

On Mon, 05 Aug 2019 11:11:56 +0200,
Christoph Hellwig wrote:
> 
> Replace the local hack with the dma_can_mmap helper to check if
> a given device supports mapping DMA allocations to userspace.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  sound/core/pcm_native.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index 703857aab00f..81c82c3ee8a2 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -220,12 +220,11 @@ static bool hw_support_mmap(struct snd_pcm_substream *substream)
>  {
>  	if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_MMAP))
>  		return false;
> -	/* architecture supports dma_mmap_coherent()? */
> -#if defined(CONFIG_ARCH_NO_COHERENT_DMA_MMAP) || !defined(CONFIG_HAS_DMA)
> +	if (!dma_can_mmap(substream->dma_buffer.dev.dev))
> +		return false;
>  	if (!substream->ops->mmap &&
>  	    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
>  		return false;
> -#endif

This won't work as expected, unfortunately.  It's a bit tricky check,
since the driver may have its own mmap implementation via
substream->ops->mmap, and the dma_buffer.dev.dev might point to
another object depending on the dma_buffer.dev.type.

So please replace with something like below:

--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -221,11 +221,10 @@ static bool hw_support_mmap(struct snd_pcm_substream *substream)
 	if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_MMAP))
 		return false;
 	/* architecture supports dma_mmap_coherent()? */
-#if defined(CONFIG_ARCH_NO_COHERENT_DMA_MMAP) || !defined(CONFIG_HAS_DMA)
 	if (!substream->ops->mmap &&
-	    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
+	    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV &&
+	    !dma_can_mmap(substream->dma_buffer.dev.dev))
 		return false;
-#endif
 	return true;
 }
 
 

Thanks!

Takashi

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_*
  2019-08-05  9:22   ` Takashi Iwai
@ 2019-08-06  5:29     ` Christoph Hellwig
  2019-08-06  6:00       ` Takashi Iwai
  0 siblings, 1 reply; 11+ messages in thread
From: Christoph Hellwig @ 2019-08-06  5:29 UTC (permalink / raw)
  To: Takashi Iwai
  Cc: Christoph Hellwig, iommu, Marek Szyprowski, Robin Murphy,
	Michal Simek, linux-arm-kernel, linux-m68k, linux-parisc,
	linux-sh, linux-xtensa, linuxppc-dev, x86, linux-kernel

On Mon, Aug 05, 2019 at 11:22:03AM +0200, Takashi Iwai wrote:
> This won't work as expected, unfortunately.  It's a bit tricky check,
> since the driver may have its own mmap implementation via
> substream->ops->mmap, and the dma_buffer.dev.dev might point to
> another object depending on the dma_buffer.dev.type.
> 
> So please replace with something like below:

From my gut feeling I'd reorder it a bit to make it more clear like
this:

http://git.infradead.org/users/hch/misc.git/commitdiff/958fccf54d00c16740522f818d23f9350498e911

if this is fine it'll be in the next version, waiting for a little more
feedback on the other patches.

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_*
  2019-08-06  5:29     ` Christoph Hellwig
@ 2019-08-06  6:00       ` Takashi Iwai
  0 siblings, 0 replies; 11+ messages in thread
From: Takashi Iwai @ 2019-08-06  6:00 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Takashi Iwai, iommu, Marek Szyprowski, Robin Murphy,
	Michal Simek, linux-arm-kernel, linux-m68k, linux-parisc,
	linux-sh, linux-xtensa, linuxppc-dev, x86, linux-kernel

On Tue, 06 Aug 2019 07:29:49 +0200,
Christoph Hellwig wrote:
> 
> On Mon, Aug 05, 2019 at 11:22:03AM +0200, Takashi Iwai wrote:
> > This won't work as expected, unfortunately.  It's a bit tricky check,
> > since the driver may have its own mmap implementation via
> > substream->ops->mmap, and the dma_buffer.dev.dev might point to
> > another object depending on the dma_buffer.dev.type.
> > 
> > So please replace with something like below:
> 
> >From my gut feeling I'd reorder it a bit to make it more clear like
> this:
> 
> http://git.infradead.org/users/hch/misc.git/commitdiff/958fccf54d00c16740522f818d23f9350498e911
> 
> if this is fine it'll be in the next version, waiting for a little more
> feedback on the other patches.

Yes, the new one looks good.
Reviewed-by: Takashi Iwai <tiwai@suse.de>


Thanks!

Takashi

^ permalink raw reply	[flat|nested] 11+ messages in thread

end of thread, back to index

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
2019-08-05  9:11 ` [PATCH 1/7] dma-mapping: move the dma_get_sgtable API comments from arm to common code Christoph Hellwig
2019-08-05  9:11 ` [PATCH 2/7] dma-mapping: explicitly wire up ->mmap and ->get_sgtable Christoph Hellwig
2019-08-05  9:11 ` [PATCH 3/7] dma-mapping: add a dma_can_mmap helper Christoph Hellwig
2019-08-05  9:11 ` [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_* Christoph Hellwig
2019-08-05  9:22   ` Takashi Iwai
2019-08-06  5:29     ` Christoph Hellwig
2019-08-06  6:00       ` Takashi Iwai
2019-08-05  9:11 ` [PATCH 5/7] m68knommu: add a pgprot_noncached stub Christoph Hellwig
2019-08-05  9:11 ` [PATCH 6/7] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP Christoph Hellwig
2019-08-05  9:11 ` [PATCH 7/7] dma-mapping: provide a better default ->get_required_mask Christoph Hellwig

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