From: Christoph Hellwig <hch@lst.de>
Date: Mon, 29 Jun 2020 15:03:56 +0200
Subject: dma-mapping: Add a new dma_need_sync API
Git-commit: 3aa91625007807bfca4155df1867a5c924a08662
Patch-mainline: v5.8-rc5
References: bsc#1175713

Add a new API to check if calls to dma_sync_single_for_{device,cpu} are
required for a given DMA streaming mapping.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200629130359.2690853-2-hch@lst.de

Acked-by: Joerg Roedel <jroedel@suse.de>
---
 Documentation/DMA-API.txt   |    8 ++++++++
 include/linux/dma-direct.h  |    1 +
 include/linux/dma-mapping.h |    5 +++++
 kernel/dma/direct.c         |    6 ++++++
 kernel/dma/mapping.c        |   10 ++++++++++
 5 files changed, 30 insertions(+)

--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -206,6 +206,14 @@ others should not be larger than the ret
 
 ::
 
+	bool
+	dma_need_sync(struct device *dev, dma_addr_t dma_addr);
+
+Returns %true if dma_sync_single_for_{device,cpu} calls are required to
+transfer memory ownership.  Returns %false if those calls can be skipped.
+
+::
+
 	unsigned long
 	dma_get_merge_boundary(struct device *dev);
 
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -85,4 +85,5 @@ int dma_direct_mmap(struct device *dev,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		unsigned long attrs);
 int dma_direct_supported(struct device *dev, u64 mask);
+bool dma_direct_need_sync(struct device *dev, dma_addr_t dma_addr);
 #endif /* _LINUX_DMA_DIRECT_H */
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -461,6 +461,7 @@ int dma_set_mask(struct device *dev, u64
 int dma_set_coherent_mask(struct device *dev, u64 mask);
 u64 dma_get_required_mask(struct device *dev);
 size_t dma_max_mapping_size(struct device *dev);
+bool dma_need_sync(struct device *dev, dma_addr_t dma_addr);
 unsigned long dma_get_merge_boundary(struct device *dev);
 #else /* CONFIG_HAS_DMA */
 static inline dma_addr_t dma_map_page_attrs(struct device *dev,
@@ -571,6 +572,10 @@ static inline size_t dma_max_mapping_siz
 {
 	return 0;
 }
+static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
+{
+	return false;
+}
 static inline unsigned long dma_get_merge_boundary(struct device *dev)
 {
 	return 0;
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -539,3 +539,9 @@ size_t dma_direct_max_mapping_size(struc
 		return swiotlb_max_mapping_size(dev);
 	return SIZE_MAX;
 }
+
+bool dma_direct_need_sync(struct device *dev, dma_addr_t dma_addr)
+{
+	return !dev_is_dma_coherent(dev) ||
+		is_swiotlb_buffer(dma_to_phys(dev, dma_addr));
+}
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -397,6 +397,16 @@ size_t dma_max_mapping_size(struct devic
 }
 EXPORT_SYMBOL_GPL(dma_max_mapping_size);
 
+bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	if (dma_is_direct(ops))
+		return dma_direct_need_sync(dev, dma_addr);
+	return ops->sync_single_for_cpu || ops->sync_single_for_device;
+}
+EXPORT_SYMBOL_GPL(dma_need_sync);
+
 unsigned long dma_get_merge_boundary(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);