There are several reports that the DMA sync shortcut broke non-coherent
devices.
dev->dma_need_sync is false after the &device allocation and if a driver
didn't call dma_set_mask*(), it will still be false even if the device
is not DMA-coherent and thus needs synchronizing. Due to historical
reasons, there's still a lot of drivers not calling it.
Invert the boolean, so that the sync will be performed by default and
the shortcut will be enabled only when calling dma_set_mask*().
Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Closes: https://lore.kernel.org/lkml/46160534-5003-4809-a408-6b3a3f4921e9@xxxxxxxxxxx
Reported-by: Steven Price <steven.price@xxxxxxx>
Closes: https://lore.kernel.org/lkml/010686f5-3049-46a1-8230-7752a1b433ff@xxxxxxx
Fixes: 32ba8b823252 ("dma: avoid redundant calls for sync operations")
Signed-off-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>
---
include/linux/device.h | 4 ++--
include/linux/dma-map-ops.h | 4 ++--
include/linux/dma-mapping.h | 2 +-
kernel/dma/mapping.c | 10 +++++-----
kernel/dma/swiotlb.c | 2 +-
5 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/include/linux/device.h b/include/linux/device.h
index ed95b829f05b..d4b50accff26 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -691,7 +691,7 @@ struct device_physical_location {
* and optionall (if the coherent mask is large enough) also
* for dma allocations. This flag is managed by the dma ops
* instance from ->dma_supported.
- * @dma_need_sync: The device needs performing DMA sync operations.
+ * @dma_skip_sync: DMA sync operations can be skipped for coherent buffers.
*
* At the lowest level, every device in a Linux system is represented by an
* instance of struct device. The device structure contains the information
@@ -805,7 +805,7 @@ struct device {
bool dma_ops_bypass : 1;
#endif
#ifdef CONFIG_DMA_NEED_SYNC
- bool dma_need_sync:1;
+ bool dma_skip_sync:1;
#endif
};