Various PCI bridges (VIA PCI, Xilinx PCIe) limit DMA to only 32-bits
even if the device itself supports more. Add a single bit flag to
struct device (to be moved into the dma extension once we around it)
to flag such devices and reject larger DMA to them.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
include/linux/device.h | 3 +++
lib/dma-direct.c | 6 ++++++
2 files changed, 9 insertions(+)
diff --git a/include/linux/device.h b/include/linux/device.h
index 477956990f5e..fa317e45f5e6 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -904,6 +904,8 @@ struct dev_links_info {
* @offline: Set after successful invocation of bus type's .offline().
* @of_node_reused: Set if the device-tree node is shared with an ancestor
* device.
+ * @dma_32bit_limit: bridge limited to 32bit DMA even if the device itself
+ * indicates support for a higher limit in the dma_mask field.
*
* At the lowest level, every device in a Linux system is represented by an
* instance of struct device. The device structure contains the information
@@ -992,6 +994,7 @@ struct device {
bool offline_disabled:1;
bool offline:1;
bool of_node_reused:1;
+ bool dma_32bit_limit:1;
};
static inline struct device *kobj_to_dev(struct kobject *kobj)
diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index bbfb229aa067..0151a7b2bc87 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -165,6 +165,12 @@ int dma_direct_supported(struct device *dev, u64 mask)
if (mask < DMA_BIT_MASK(32))
return 0;
#endif
+ /*
+ * Various PCI/PCIe bridges have broken support for > 32bit DMA even
+ * if the device itself might support it.
+ */
+ if (dev->dma_32bit_limit && mask > DMA_BIT_MASK(32))
+ return 0;
return 1;
}
--
2.17.0
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