On 09.05.2024 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> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > --- > 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 > }; > > diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h > index 4893cb89cb52..5217b922d29f 100644 > --- a/include/linux/dma-map-ops.h > +++ b/include/linux/dma-map-ops.h > @@ -280,8 +280,8 @@ static inline void dma_reset_need_sync(struct device *dev) > { > #ifdef CONFIG_DMA_NEED_SYNC > /* Reset it only once so that the function can be called on hotpath */ > - if (unlikely(!dev->dma_need_sync)) > - dev->dma_need_sync = true; > + if (unlikely(dev->dma_skip_sync)) > + dev->dma_skip_sync = false; > #endif > } > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index eb4e15893b6c..f693aafe221f 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -295,7 +295,7 @@ bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr); > static inline bool dma_dev_need_sync(const struct device *dev) > { > /* Always call DMA sync operations when debugging is enabled */ > - return dev->dma_need_sync || IS_ENABLED(CONFIG_DMA_API_DEBUG); > + return !dev->dma_skip_sync || IS_ENABLED(CONFIG_DMA_API_DEBUG); > } > > static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, > diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c > index 3524bc92c37f..3f77c3f8d16d 100644 > --- a/kernel/dma/mapping.c > +++ b/kernel/dma/mapping.c > @@ -392,7 +392,7 @@ bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr) > > if (dma_map_direct(dev, ops)) > /* > - * dma_need_sync could've been reset on first SWIOTLB buffer > + * dma_skip_sync could've been reset on first SWIOTLB buffer > * mapping, but @dma_addr is not necessary an SWIOTLB buffer. > * In this case, fall back to more granular check. > */ > @@ -407,20 +407,20 @@ static void dma_setup_need_sync(struct device *dev) > > if (dma_map_direct(dev, ops) || (ops->flags & DMA_F_CAN_SKIP_SYNC)) > /* > - * dma_need_sync will be reset to %true on first SWIOTLB buffer > + * dma_skip_sync will be reset to %false on first SWIOTLB buffer > * mapping, if any. During the device initialization, it's > * enough to check only for the DMA coherence. > */ > - dev->dma_need_sync = !dev_is_dma_coherent(dev); > + dev->dma_skip_sync = dev_is_dma_coherent(dev); > else if (!ops->sync_single_for_device && !ops->sync_single_for_cpu && > !ops->sync_sg_for_device && !ops->sync_sg_for_cpu) > /* > * Synchronization is not possible when none of DMA sync ops > * is set. > */ > - dev->dma_need_sync = false; > + dev->dma_skip_sync = true; > else > - dev->dma_need_sync = true; > + dev->dma_skip_sync = false; > } > #else /* !CONFIG_DMA_NEED_SYNC */ > static inline void dma_setup_need_sync(struct device *dev) { } > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index ae3e593eaadb..068134697cf1 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -1409,7 +1409,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr, > } > > /* > - * If dma_need_sync wasn't set, reset it on first SWIOTLB buffer > + * If dma_skip_sync was set, reset it on first SWIOTLB buffer > * mapping to always sync SWIOTLB buffers. > */ > dma_reset_need_sync(dev); Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
