[PATCH v9 16/18] PCI/P2PDMA: Let a client declare that it selects ATS per mapping

[Leon Romanovsky]

From: Leon Romanovsky <leonro@xxxxxxxxxx>

The PCIe ATS Enable bit covers the whole device, so P2PDMA cannot tell
from it whether a client will translate a given address. Most devices
translate any address once ATS is enabled, but some choose ATS per DMA
mapping and can still use bus addresses for the rest.

Add pcim_p2pdma_set_ats_per_mapping() so the driver of such a device can
declare that before P2PDMA starts treating clients with ATS enabled as
translating everything. Keep it in the device's P2PDMA state, which
already ends with the driver binding.

Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
---
 drivers/pci/p2pdma.c       | 27 +++++++++++++++++++++++++++
 include/linux/pci-p2pdma.h |  4 ++++
 2 files changed, 31 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index c1e9d43bded2..126e28d2a5dd 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -26,6 +26,7 @@
 struct pci_p2pdma {
 	struct gen_pool *pool;
 	bool p2pmem_published;
+	bool ats_per_mapping;
 	struct xarray map_types;
 	struct p2pdma_provider mem[PCI_STD_NUM_BARS];
 };
@@ -1568,6 +1569,32 @@ void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
 
+/**
+ * pcim_p2pdma_set_ats_per_mapping - Declare per-mapping ATS for a client
+ * @pdev: PCI device that initiates peer-to-peer DMA
+ *
+ * Declare that @pdev issues Translated Requests only for the DMA mappings its
+ * driver sets up to use ATS, rather than for any address once ATS is enabled.
+ * P2PDMA then routes this client's Requests with the Address Type each query
+ * asks about, rather than the one its ATS Enable bit implies.
+ */
+void pcim_p2pdma_set_ats_per_mapping(struct pci_dev *pdev)
+{
+	struct pci_p2pdma *p2p;
+
+	p2p = rcu_dereference_protected(pdev->p2pdma, 1);
+	if (!p2p)
+		/*
+		 * ats_per_mapping is a performance optimization,
+		 * if pcim_p2pdma_init() didn't set pdev->p2pdma pointer
+		 * for some reason, let's simply use ATS global settings.
+		 */
+		return;
+
+	p2p->ats_per_mapping = true;
+}
+EXPORT_SYMBOL_GPL(pcim_p2pdma_set_ats_per_mapping);
+
 /**
  * pci_p2pdma_map_type_tlp - Determine the mapping type for P2PDMA transfers
  * @provider: P2PDMA provider structure
diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index dd17501ba1b6..ce389e18d023 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -82,6 +82,7 @@ struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,
 					 unsigned int *nents, u32 length);
 void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl);
 void pci_p2pmem_publish(struct pci_dev *pdev, bool publish);
+void pcim_p2pdma_set_ats_per_mapping(struct pci_dev *pdev);
 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,
@@ -138,6 +139,9 @@ 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 void pcim_p2pdma_set_ats_per_mapping(struct pci_dev *pdev)
+{
+}
 static inline int pci_p2pdma_enable_store(const char *page,
 		struct pci_dev **p2p_dev, bool *use_p2pdma)
 {

-- 
2.55.0