Add pci_p2pdma_map_segment() as a helper for simple dma_map_sg() implementations. It takes an scatterlist segment that must point to a pci_p2pdma struct page and will map it if the mapping requires a bus address. The return value indicates whether the mapping required a bus address or whether the caller still needs to map the segment normally. If the segment should not be mapped, -EREMOTEIO is returned. This helper uses a state structure to track the changes to the pgmap across calls and avoid needing to lookup into the xarray for every page. Also add pci_p2pdma_map_bus_segment() which is useful for IOMMU dma_map_sg() implementations where the sg segment containing the page differs from the sg segment containing the DMA address. Prototypes for these helpers are added to dma-map-ops.h as they are only useful to dma map implementations and don't need to pollute the public pci-p2pdma header. Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> --- drivers/pci/p2pdma.c | 59 +++++++++++++++++++++++++++++++++++++ include/linux/dma-map-ops.h | 21 +++++++++++++ 2 files changed, 80 insertions(+) diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 8573bf9d651a..9032c2ed2cdf 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -946,6 +946,65 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg, } EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs); +/** + * pci_p2pdma_map_segment - map an sg segment determining the mapping type + * @state: State structure that should be declared outside of the for_each_sg() + * loop and initialized to zero. + * @dev: DMA device that's doing the mapping operation + * @sg: scatterlist segment to map + * + * This is a helper to be used by non-IOMMU dma_map_sg() implementations where + * the sg segment is the same for the page_link and the dma_address. + * + * Attempt to map a single segment in an SGL with the PCI bus address. + * The segment must point to a PCI P2PDMA page and thus must be + * wrapped in a is_pci_p2pdma_page(sg_page(sg)) check. + * + * Returns the type of mapping used and maps the page if the type is + * PCI_P2PDMA_MAP_BUS_ADDR. + */ +enum pci_p2pdma_map_type +pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev, + struct scatterlist *sg) +{ + if (state->pgmap != sg_page(sg)->pgmap) { + state->pgmap = sg_page(sg)->pgmap; + state->map = pci_p2pdma_map_type(state->pgmap, dev); + state->bus_off = to_p2p_pgmap(state->pgmap)->bus_offset; + } + + if (state->map == PCI_P2PDMA_MAP_BUS_ADDR) { + sg->dma_address = sg_phys(sg) + state->bus_off; + sg_dma_len(sg) = sg->length; + sg_dma_mark_bus_address(sg); + } + + return state->map; +} + +/** + * pci_p2pdma_map_bus_segment - map an sg segment pre determined to + * be mapped with PCI_P2PDMA_MAP_BUS_ADDR + * @pg_sg: scatterlist segment with the page to map + * @dma_sg: scatterlist segment to assign a DMA address to + * + * This is a helper for iommu dma_map_sg() implementations when the + * segment for the DMA address differs from the segment containing the + * source page. + * + * pci_p2pdma_map_type() must have already been called on the pg_sg and + * returned PCI_P2PDMA_MAP_BUS_ADDR. + */ +void pci_p2pdma_map_bus_segment(struct scatterlist *pg_sg, + struct scatterlist *dma_sg) +{ + struct pci_p2pdma_pagemap *pgmap = to_p2p_pgmap(sg_page(pg_sg)->pgmap); + + dma_sg->dma_address = sg_phys(pg_sg) + pgmap->bus_offset; + sg_dma_len(dma_sg) = pg_sg->length; + sg_dma_mark_bus_address(dma_sg); +} + /** * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store * to enable p2pdma diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h index d693a0e33bac..752f91e5eb5d 100644 --- a/include/linux/dma-map-ops.h +++ b/include/linux/dma-map-ops.h @@ -413,15 +413,36 @@ enum pci_p2pdma_map_type { PCI_P2PDMA_MAP_THRU_HOST_BRIDGE, }; +struct pci_p2pdma_map_state { + struct dev_pagemap *pgmap; + int map; + u64 bus_off; +}; + #ifdef CONFIG_PCI_P2PDMA enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap, struct device *dev); +enum pci_p2pdma_map_type +pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev, + struct scatterlist *sg); +void pci_p2pdma_map_bus_segment(struct scatterlist *pg_sg, + struct scatterlist *dma_sg); #else /* CONFIG_PCI_P2PDMA */ static inline enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap, struct device *dev) { return PCI_P2PDMA_MAP_NOT_SUPPORTED; } +static inline enum pci_p2pdma_map_type +pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev, + struct scatterlist *sg) +{ + return PCI_P2PDMA_MAP_NOT_SUPPORTED; +} +static inline void pci_p2pdma_map_bus_segment(struct scatterlist *pg_sg, + struct scatterlist *dma_sg) +{ +} #endif /* CONFIG_PCI_P2PDMA */ #endif /* _LINUX_DMA_MAP_OPS_H */ -- 2.30.2