| Message ID | 00385b3557fa074865d37b0ac613d2cb28bcb741.1730298502.git.leon@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Provide a new two step DMA mapping API | expand |
On 30/10/2024 3:12 pm, Leon Romanovsky wrote: > From: Christoph Hellwig <hch@lst.de> > > Add helper that allows a driver to skip calling dma_unmap_* > if the DMA layer can guarantee that they are no-nops. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > Signed-off-by: Leon Romanovsky <leonro@nvidia.com> > --- > include/linux/dma-mapping.h | 5 +++++ > kernel/dma/mapping.c | 20 ++++++++++++++++++++ > 2 files changed, 25 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 8074a3b5c807..6906edde505d 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -410,6 +410,7 @@ static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr) > { > return dma_dev_need_sync(dev) ? __dma_need_sync(dev, dma_addr) : false; > } > +bool dma_need_unmap(struct device *dev); > #else /* !CONFIG_HAS_DMA || !CONFIG_DMA_NEED_SYNC */ > static inline bool dma_dev_need_sync(const struct device *dev) > { > @@ -435,6 +436,10 @@ static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr) > { > return false; > } > +static inline bool dma_need_unmap(struct device *dev) > +{ > + return false; > +} > #endif /* !CONFIG_HAS_DMA || !CONFIG_DMA_NEED_SYNC */ > > struct page *dma_alloc_pages(struct device *dev, size_t size, > diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c > index 864a1121bf08..daa97a650778 100644 > --- a/kernel/dma/mapping.c > +++ b/kernel/dma/mapping.c > @@ -442,6 +442,26 @@ bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr) > } > EXPORT_SYMBOL_GPL(__dma_need_sync); > > +/** > + * dma_need_unmap - does this device need dma_unmap_* operations > + * @dev: device to check > + * > + * If this function returns %false, drivers can skip calling dma_unmap_* after > + * finishing an I/O. This function must be called after all mappings that might > + * need to be unmapped have been performed. In terms of the unmap call itself, why don't we just use dma_skip_sync to short-cut dma_direct_unmap_*() and make sure it's as cheap as possible? In terms of not having to unmap implying not having to store addresses at all, it doesn't seem super-useful when you still have to store them for long enough to find out that you don't :/ Thanks, Robin. > + */ > +bool dma_need_unmap(struct device *dev) > +{ > + if (!dma_map_direct(dev, get_dma_ops(dev))) > + return true; > +#ifdef CONFIG_DMA_NEED_SYNC > + if (!dev->dma_skip_sync) > + return true; > +#endif > + return IS_ENABLED(CONFIG_DMA_API_DEBUG); > +} > +EXPORT_SYMBOL_GPL(dma_need_unmap); > + > static void dma_setup_need_sync(struct device *dev) > { > const struct dma_map_ops *ops = get_dma_ops(dev);
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 8074a3b5c807..6906edde505d 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -410,6 +410,7 @@ static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr) { return dma_dev_need_sync(dev) ? __dma_need_sync(dev, dma_addr) : false; } +bool dma_need_unmap(struct device *dev); #else /* !CONFIG_HAS_DMA || !CONFIG_DMA_NEED_SYNC */ static inline bool dma_dev_need_sync(const struct device *dev) { @@ -435,6 +436,10 @@ static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr) { return false; } +static inline bool dma_need_unmap(struct device *dev) +{ + return false; +} #endif /* !CONFIG_HAS_DMA || !CONFIG_DMA_NEED_SYNC */ struct page *dma_alloc_pages(struct device *dev, size_t size, diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 864a1121bf08..daa97a650778 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -442,6 +442,26 @@ bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr) } EXPORT_SYMBOL_GPL(__dma_need_sync); +/** + * dma_need_unmap - does this device need dma_unmap_* operations + * @dev: device to check + * + * If this function returns %false, drivers can skip calling dma_unmap_* after + * finishing an I/O. This function must be called after all mappings that might + * need to be unmapped have been performed. + */ +bool dma_need_unmap(struct device *dev) +{ + if (!dma_map_direct(dev, get_dma_ops(dev))) + return true; +#ifdef CONFIG_DMA_NEED_SYNC + if (!dev->dma_skip_sync) + return true; +#endif + return IS_ENABLED(CONFIG_DMA_API_DEBUG); +} +EXPORT_SYMBOL_GPL(dma_need_unmap); + static void dma_setup_need_sync(struct device *dev) { const struct dma_map_ops *ops = get_dma_ops(dev);