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Subject[RFC PATCH 1/5] pci/p2p: add a function to test peer to peer capability
Date
From: Jérôme Glisse <jglisse@redhat.com>

device_test_p2p() return true if two devices can peer to peer to
each other. We add a generic function as different inter-connect
can support peer to peer and we want to genericaly test this no
matter what the inter-connect might be. However this version only
support PCIE for now.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: Christoph Hellwig <hch@lst.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: iommu@lists.linux-foundation.org
---
drivers/pci/p2pdma.c | 27 +++++++++++++++++++++++++++
include/linux/pci-p2pdma.h | 6 ++++++
2 files changed, 33 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index c52298d76e64..620ac60babb5 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -797,3 +797,30 @@ ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
return sprintf(page, "%s\n", pci_name(p2p_dev));
}
EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);
+
+bool pci_test_p2p(struct device *devA, struct device *devB)
+{
+ struct pci_dev *pciA, *pciB;
+ bool ret;
+ int tmp;
+
+ /*
+ * For now we only support PCIE peer to peer but other inter-connect
+ * can be added.
+ */
+ pciA = find_parent_pci_dev(devA);
+ pciB = find_parent_pci_dev(devB);
+ if (pciA == NULL || pciB == NULL) {
+ ret = false;
+ goto out;
+ }
+
+ tmp = upstream_bridge_distance(pciA, pciB, NULL);
+ ret = tmp < 0 ? false : true;
+
+out:
+ pci_dev_put(pciB);
+ pci_dev_put(pciA);
+ return false;
+}
+EXPORT_SYMBOL_GPL(pci_test_p2p);
diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index bca9bc3e5be7..7671cc499a08 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -36,6 +36,7 @@ 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,
bool use_p2pdma);
+bool pci_test_p2p(struct device *devA, struct device *devB);
#else /* CONFIG_PCI_P2PDMA */
static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar,
size_t size, u64 offset)
@@ -97,6 +98,11 @@ static inline ssize_t pci_p2pdma_enable_show(char *page,
{
return sprintf(page, "none\n");
}
+
+static inline bool pci_test_p2p(struct device *devA, struct device *devB)
+{
+ return false;
+}
#endif /* CONFIG_PCI_P2PDMA */


--
2.17.2
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