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authorBjorn Helgaas <bhelgaas@google.com>2016-06-13 18:01:51 +0200
committerBjorn Helgaas <bhelgaas@google.com>2016-08-18 23:04:57 +0200
commiteec097d43100a8195fd4f678671ecd5d986dd675 (patch)
treeec874686b415958f9123b68f4ba0f85bae6b8c86 /drivers/pci/pcie
parentPCI: Add Precision Time Measurement (PTM) support (diff)
downloadlinux-eec097d43100a8195fd4f678671ecd5d986dd675.tar.xz
linux-eec097d43100a8195fd4f678671ecd5d986dd675.zip
PCI: Add pci_enable_ptm() for drivers to enable PTM on endpoints
Add an pci_enable_ptm() interface so drivers can enable PTM. The PCI core enables PTM on PTM Roots and switches automatically, but we don't enable PTM on endpoints unless a driver requests it. Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers/pci/pcie')
-rw-r--r--drivers/pci/pcie/ptm.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
index 48eea4e65247..a14ac94b96dc 100644
--- a/drivers/pci/pcie/ptm.c
+++ b/drivers/pci/pcie/ptm.c
@@ -68,3 +68,48 @@ void pci_ptm_init(struct pci_dev *dev)
pci_ptm_info(dev);
}
+
+int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
+{
+ int pos;
+ u32 cap, ctrl;
+ struct pci_dev *ups;
+
+ if (!pci_is_pcie(dev))
+ return -EINVAL;
+
+ pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);
+ if (!pos)
+ return -EINVAL;
+
+ pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
+ if (!(cap & PCI_PTM_CAP_REQ))
+ return -EINVAL;
+
+ /*
+ * For a PCIe Endpoint, PTM is only useful if the endpoint can
+ * issue PTM requests to upstream devices that have PTM enabled.
+ *
+ * For Root Complex Integrated Endpoints, there is no upstream
+ * device, so there must be some implementation-specific way to
+ * associate the endpoint with a time source.
+ */
+ if (pci_pcie_type(dev) == PCI_EXP_TYPE_ENDPOINT) {
+ ups = pci_upstream_bridge(dev);
+ if (!ups || !ups->ptm_enabled)
+ return -EINVAL;
+ } else if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
+ } else
+ return -EINVAL;
+
+ ctrl = PCI_PTM_CTRL_ENABLE;
+ pci_write_config_dword(dev, pos + PCI_PTM_CTRL, ctrl);
+ dev->ptm_enabled = 1;
+
+ pci_ptm_info(dev);
+
+ if (granularity)
+ *granularity = 0;
+ return 0;
+}
+EXPORT_SYMBOL(pci_enable_ptm);