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>
diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
index 48eea4e..a14ac94 100644
--- a/drivers/pci/pcie/ptm.c
+++ b/drivers/pci/pcie/ptm.c
@@ -68,3 +68,48 @@
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);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 96c509f..9e4b6d6 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1407,6 +1407,13 @@
static inline int pci_ats_queue_depth(struct pci_dev *d) { return -ENODEV; }
#endif
+#ifdef CONFIG_PCIE_PTM
+int pci_enable_ptm(struct pci_dev *dev, u8 *granularity);
+#else
+static inline int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
+{ return -EINVAL; }
+#endif
+
void pci_cfg_access_lock(struct pci_dev *dev);
bool pci_cfg_access_trylock(struct pci_dev *dev);
void pci_cfg_access_unlock(struct pci_dev *dev);
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 926fff4..72bbe14 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -967,6 +967,7 @@
/* Precision Time Measurement */
#define PCI_PTM_CAP 0x04 /* PTM Capability */
+#define PCI_PTM_CAP_REQ 0x00000001 /* Requester capable */
#define PCI_PTM_CAP_ROOT 0x00000004 /* Root capable */
#define PCI_PTM_CTRL 0x08 /* PTM Control */
#define PCI_PTM_CTRL_ENABLE 0x00000001 /* PTM enable */