[PATCH v2 2/5] dma-direct: add dma_direct_bypass() to force direct ops

[Jonathan Marek <jonathan@marek.ca>]

Add a function to force direct ops and disable swiotlb for a deivce.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
---
 include/linux/dma-direct.h |  9 +++++++++
 kernel/dma/direct.c        | 23 +++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index 18aade195884..41f57e1b7aa5 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -124,4 +124,13 @@ int dma_direct_supported(struct device *dev, u64 mask);
 dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs);
 
+#if IS_ENABLED(CONFIG_DMA_OPS_BYPASS) && !IS_ENABLED(CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED)
+int dma_direct_bypass(struct device *dev);
+#else
+static inline int dma_direct_bypass(struct device *dev)
+{
+	return -EIO;
+}
+#endif
+
 #endif /* _LINUX_DMA_DIRECT_H */
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 06c111544f61..304a5a77cccb 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -548,3 +548,26 @@ int dma_direct_set_offset(struct device *dev, phys_addr_t cpu_start,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(dma_direct_set_offset);
+
+/**
+ * dma_direct_bypass - always use direct mapping path for device
+ * @dev:	device pointer
+ *
+ * Note: this also bypasses swiotlb. Not available for arch with
+ * force_dma_unencrypted(), since this doesn't deal with that.
+ */
+#if IS_ENABLED(CONFIG_DMA_OPS_BYPASS) && !IS_ENABLED(CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED)
+int dma_direct_bypass(struct device *dev)
+{
+	int ret;
+
+	ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
+	if (ret)
+		return ret;
+
+	dev->bus_dma_limit = DMA_BIT_MASK(64);
+	dev->dma_ops_bypass = true;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dma_direct_bypass);
+#endif
-- 
2.26.1