On 5/9/24 16:46, Alexander Lobakin wrote:
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 };
very good solution with inverting the flag, Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx> // ...
