Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2 1/3] dma-mapping: introduce new dma unmap and sync api variants | From | Robin Murphy <> | Date | Mon, 28 Oct 2019 13:42:43 +0000 |
| |
On 24/10/2019 13:41, Laurentiu Tudor wrote: > From: Laurentiu Tudor <laurentiu.tudor@nxp.com> > > Introduce a few new dma unmap and sync variants that, on top of the > original variants, return the virtual address corresponding to the > input dma address. > In order to implement this a new dma map op is added and used: > void *get_virt_addr(dev, dma_handle); > It does the actual conversion of an input dma address to the output > virtual address.
At this point, I think it might be better to just change the prototype of the .unmap_page/.sync_single_for_cpu callbacks themselves. In cases where .get_virt_addr would be non-trivial, it's most likely duplicating work that the relevant callback has to do anyway (i.e. where the virtual and/or physical address is needed internally for a cache maintenance or bounce buffer operation). It would also help avoid any possible ambiguity about whether .get_virt_addr returns the VA corresponding dma_handle (if one exists) rather than the VA of the buffer *mapped to* dma_handle, which for a bounce-buffering implementation would be different, and the one you actually need - a naive phys_to_virt(dma_to_phys(dma_handle)) would lead you to the wrong place (in fact it looks like DPAA2 would currently go wrong with "swiotlb=force" and the SMMU disabled or in passthrough).
One question there is whether we'd want careful special-casing to avoid introducing overhead where unmap/sync are currently complete no-ops, or whether an extra phys_to_virt() or so in those paths would be tolerable.
> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com> > --- > include/linux/dma-mapping.h | 55 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 55 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 4a1c4fca475a..ae7bb8a84b9d 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -132,6 +132,7 @@ struct dma_map_ops { > u64 (*get_required_mask)(struct device *dev); > size_t (*max_mapping_size)(struct device *dev); > unsigned long (*get_merge_boundary)(struct device *dev); > + void *(*get_virt_addr)(struct device *dev, dma_addr_t dma_handle); > }; > > #define DMA_MAPPING_ERROR (~(dma_addr_t)0) > @@ -304,6 +305,21 @@ static inline void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, > debug_dma_unmap_page(dev, addr, size, dir); > } > > +static inline struct page * > +dma_unmap_page_attrs_desc(struct device *dev, dma_addr_t addr, size_t size, > + enum dma_data_direction dir, unsigned long attrs) > +{ > + const struct dma_map_ops *ops = get_dma_ops(dev); > + void *ptr = NULL; > + > + if (ops && ops->get_virt_addr) > + ptr = ops->get_virt_addr(dev, addr);
Note that this doesn't work for dma-direct, but for the sake of arm64 at least it almost certainly wants to.
Robin.
> + dma_unmap_page_attrs(dev, addr, size, dir, attrs); > + > + return ptr ? virt_to_page(ptr) : NULL; > +} > + > /* > * dma_maps_sg_attrs returns 0 on error and > 0 on success. > * It should never return a value < 0. > @@ -390,6 +406,21 @@ static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, > debug_dma_sync_single_for_cpu(dev, addr, size, dir); > } > > +static inline void * > +dma_sync_single_for_cpu_desc(struct device *dev, dma_addr_t addr, size_t size, > + enum dma_data_direction dir) > +{ > + const struct dma_map_ops *ops = get_dma_ops(dev); > + void *ptr = NULL; > + > + if (ops && ops->get_virt_addr) > + ptr = ops->get_virt_addr(dev, addr); > + > + dma_sync_single_for_cpu(dev, addr, size, dir); > + > + return ptr; > +} > + > static inline void dma_sync_single_for_device(struct device *dev, > dma_addr_t addr, size_t size, > enum dma_data_direction dir) > @@ -500,6 +531,12 @@ static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, > size_t size, enum dma_data_direction dir) > { > } > + > +static inline void * > +dma_sync_single_for_cpu_desc(struct device *dev, dma_addr_t addr, size_t size, > + enum dma_data_direction dir) > +{ > +} > static inline void dma_sync_single_for_device(struct device *dev, > dma_addr_t addr, size_t size, enum dma_data_direction dir) > { > @@ -594,6 +631,21 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr, > return dma_unmap_page_attrs(dev, addr, size, dir, attrs); > } > > +static inline void * > +dma_unmap_single_attrs_desc(struct device *dev, dma_addr_t addr, size_t size, > + enum dma_data_direction dir, unsigned long attrs) > +{ > + const struct dma_map_ops *ops = get_dma_ops(dev); > + void *ptr = NULL; > + > + if (ops && ops->get_virt_addr) > + ptr = ops->get_virt_addr(dev, addr); > + > + dma_unmap_single_attrs(dev, addr, size, dir, attrs); > + > + return ptr; > +} > + > static inline void dma_sync_single_range_for_cpu(struct device *dev, > dma_addr_t addr, unsigned long offset, size_t size, > enum dma_data_direction dir) > @@ -610,10 +662,13 @@ static inline void dma_sync_single_range_for_device(struct device *dev, > > #define dma_map_single(d, a, s, r) dma_map_single_attrs(d, a, s, r, 0) > #define dma_unmap_single(d, a, s, r) dma_unmap_single_attrs(d, a, s, r, 0) > +#define dma_unmap_single_desc(d, a, s, r) \ > + dma_unmap_single_attrs_desc(d, a, s, r, 0) > #define dma_map_sg(d, s, n, r) dma_map_sg_attrs(d, s, n, r, 0) > #define dma_unmap_sg(d, s, n, r) dma_unmap_sg_attrs(d, s, n, r, 0) > #define dma_map_page(d, p, o, s, r) dma_map_page_attrs(d, p, o, s, r, 0) > #define dma_unmap_page(d, a, s, r) dma_unmap_page_attrs(d, a, s, r, 0) > +#define dma_unmap_page_desc(d, a, s, r) dma_unmap_page_attrs_desc(d, a, s, r, 0) > #define dma_get_sgtable(d, t, v, h, s) dma_get_sgtable_attrs(d, t, v, h, s, 0) > #define dma_mmap_coherent(d, v, c, h, s) dma_mmap_attrs(d, v, c, h, s, 0) > >
| |