[RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()

Logan Gunthorpe
2021-03-11T23:48:46Z

Introduce pci_p2pdma_should_map_bus() which is meant to be called by
DMA map functions to determine how to map a given p2pdma page.

pci_p2pdma_bus_offset() is also added to allow callers to get the bus
offset if they need to map the bus address.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
drivers/pci/p2pdma.c | 50 ++++++++++++++++++++++++++++++++++++++
include/linux/pci-p2pdma.h | 11 +++++++++
2 files changed, 61 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 7f6836732bce..66d16b7eb668 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -912,6 +912,56 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
}
EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);

+/**
+ * pci_p2pdma_bus_offset - returns the bus offset for a given page
+ * @page: page to get the offset for
+ *
+ * Must be passed a PCI p2pdma page.
+ */
+u64 pci_p2pdma_bus_offset(struct page *page)
+{
+ struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(page->pgmap);
+
+ WARN_ON(!is_pci_p2pdma_page(page));
+
+ return p2p_pgmap->bus_offset;
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_bus_offset);
+
+/**
+ * pci_p2pdma_dma_map_type - determine if a DMA mapping should use the
+ * bus address, be mapped normally or fail
+ * @dev: device doing the DMA request
+ * @pgmap: dev_pagemap structure for the mapping
+ *
+ * Returns:
+ * 1 - if the page should be mapped with a bus address,
+ * 0 - if the page should be mapped normally through an IOMMU mapping or
+ * physical address; or
+ * -1 - if the device should not map the pages and an error should be
+ * returned
+ */
+int pci_p2pdma_dma_map_type(struct device *dev, struct dev_pagemap *pgmap)
+{
+ struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(pgmap);
+ struct pci_dev *client;
+
+ if (!dev_is_pci(dev))
+ return -1;
+
+ client = to_pci_dev(dev);
+
+ switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) {
+ case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
+ return 0;
+ case PCI_P2PDMA_MAP_BUS_ADDR:
+ return 1;
+ default:
+ return -1;
+ }
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_dma_map_type);
+
/**
* pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
* to enable p2pdma
diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index 8318a97c9c61..3d55ad19f54c 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -34,6 +34,8 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir, unsigned long attrs);
void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir, unsigned long attrs);
+u64 pci_p2pdma_bus_offset(struct page *page);
+int pci_p2pdma_dma_map_type(struct device *dev, struct dev_pagemap *pgmap);
int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
bool *use_p2pdma);
ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
@@ -83,6 +85,15 @@ static inline void pci_p2pmem_free_sgl(struct pci_dev *pdev,
static inline void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
{
}
+static inline u64 pci_p2pdma_bus_offset(struct page *page)
+{
+ return -1;
+}
+static inline int pci_p2pdma_dma_map_type(struct device *dev,
+ struct dev_pagemap *pgmap)
+{
+ return -1;
+}
static inline int pci_p2pdma_map_sg_attrs(struct device *dev,
struct scatterlist *sg, int nents, enum dma_data_direction dir,
unsigned long attrs)
--
2.20.1