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path: root/drivers/pci/pcie/ptm.c
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Diffstat (limited to 'drivers/pci/pcie/ptm.c')
-rw-r--r--drivers/pci/pcie/ptm.c253
1 files changed, 253 insertions, 0 deletions
diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
new file mode 100644
index 0000000000..b4e5f55346
--- /dev/null
+++ b/drivers/pci/pcie/ptm.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Express Precision Time Measurement
+ * Copyright (c) 2016, Intel Corporation.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/pci.h>
+#include "../pci.h"
+
+/*
+ * If the next upstream device supports PTM, return it; otherwise return
+ * NULL. PTM Messages are local, so both link partners must support it.
+ */
+static struct pci_dev *pci_upstream_ptm(struct pci_dev *dev)
+{
+ struct pci_dev *ups = pci_upstream_bridge(dev);
+
+ /*
+ * Switch Downstream Ports are not permitted to have a PTM
+ * capability; their PTM behavior is controlled by the Upstream
+ * Port (PCIe r5.0, sec 7.9.16), so if the upstream bridge is a
+ * Switch Downstream Port, look up one more level.
+ */
+ if (ups && pci_pcie_type(ups) == PCI_EXP_TYPE_DOWNSTREAM)
+ ups = pci_upstream_bridge(ups);
+
+ if (ups && ups->ptm_cap)
+ return ups;
+
+ return NULL;
+}
+
+/*
+ * Find the PTM Capability (if present) and extract the information we need
+ * to use it.
+ */
+void pci_ptm_init(struct pci_dev *dev)
+{
+ u16 ptm;
+ u32 cap;
+ struct pci_dev *ups;
+
+ if (!pci_is_pcie(dev))
+ return;
+
+ ptm = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);
+ if (!ptm)
+ return;
+
+ dev->ptm_cap = ptm;
+ pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_PTM, sizeof(u32));
+
+ pci_read_config_dword(dev, ptm + PCI_PTM_CAP, &cap);
+ dev->ptm_granularity = (cap & PCI_PTM_GRANULARITY_MASK) >> 8;
+
+ /*
+ * Per the spec recommendation (PCIe r6.0, sec 7.9.15.3), select the
+ * furthest upstream Time Source as the PTM Root. For Endpoints,
+ * "the Effective Granularity is the maximum Local Clock Granularity
+ * reported by the PTM Root and all intervening PTM Time Sources."
+ */
+ ups = pci_upstream_ptm(dev);
+ if (ups) {
+ if (ups->ptm_granularity == 0)
+ dev->ptm_granularity = 0;
+ else if (ups->ptm_granularity > dev->ptm_granularity)
+ dev->ptm_granularity = ups->ptm_granularity;
+ } else if (cap & PCI_PTM_CAP_ROOT) {
+ dev->ptm_root = 1;
+ } else if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
+
+ /*
+ * Per sec 7.9.15.3, this should be the Local Clock
+ * Granularity of the associated Time Source. But it
+ * doesn't say how to find that Time Source.
+ */
+ dev->ptm_granularity = 0;
+ }
+
+ if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
+ pci_pcie_type(dev) == PCI_EXP_TYPE_UPSTREAM)
+ pci_enable_ptm(dev, NULL);
+}
+
+void pci_save_ptm_state(struct pci_dev *dev)
+{
+ u16 ptm = dev->ptm_cap;
+ struct pci_cap_saved_state *save_state;
+ u32 *cap;
+
+ if (!ptm)
+ return;
+
+ save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);
+ if (!save_state)
+ return;
+
+ cap = (u32 *)&save_state->cap.data[0];
+ pci_read_config_dword(dev, ptm + PCI_PTM_CTRL, cap);
+}
+
+void pci_restore_ptm_state(struct pci_dev *dev)
+{
+ u16 ptm = dev->ptm_cap;
+ struct pci_cap_saved_state *save_state;
+ u32 *cap;
+
+ if (!ptm)
+ return;
+
+ save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);
+ if (!save_state)
+ return;
+
+ cap = (u32 *)&save_state->cap.data[0];
+ pci_write_config_dword(dev, ptm + PCI_PTM_CTRL, *cap);
+}
+
+/* Enable PTM in the Control register if possible */
+static int __pci_enable_ptm(struct pci_dev *dev)
+{
+ u16 ptm = dev->ptm_cap;
+ struct pci_dev *ups;
+ u32 ctrl;
+
+ if (!ptm)
+ return -EINVAL;
+
+ /*
+ * A device uses local PTM Messages to request time information
+ * from a PTM Root that's farther upstream. Every device along the
+ * path must support PTM and have it enabled so it can handle the
+ * messages. Therefore, if this device is not a PTM Root, the
+ * upstream link partner must have PTM enabled before we can enable
+ * PTM.
+ */
+ if (!dev->ptm_root) {
+ ups = pci_upstream_ptm(dev);
+ if (!ups || !ups->ptm_enabled)
+ return -EINVAL;
+ }
+
+ pci_read_config_dword(dev, ptm + PCI_PTM_CTRL, &ctrl);
+
+ ctrl |= PCI_PTM_CTRL_ENABLE;
+ ctrl &= ~PCI_PTM_GRANULARITY_MASK;
+ ctrl |= dev->ptm_granularity << 8;
+ if (dev->ptm_root)
+ ctrl |= PCI_PTM_CTRL_ROOT;
+
+ pci_write_config_dword(dev, ptm + PCI_PTM_CTRL, ctrl);
+ return 0;
+}
+
+/**
+ * pci_enable_ptm() - Enable Precision Time Measurement
+ * @dev: PCI device
+ * @granularity: pointer to return granularity
+ *
+ * Enable Precision Time Measurement for @dev. If successful and
+ * @granularity is non-NULL, return the Effective Granularity.
+ *
+ * Return: zero if successful, or -EINVAL if @dev lacks a PTM Capability or
+ * is not a PTM Root and lacks an upstream path of PTM-enabled devices.
+ */
+int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
+{
+ int rc;
+ char clock_desc[8];
+
+ rc = __pci_enable_ptm(dev);
+ if (rc)
+ return rc;
+
+ dev->ptm_enabled = 1;
+
+ if (granularity)
+ *granularity = dev->ptm_granularity;
+
+ switch (dev->ptm_granularity) {
+ case 0:
+ snprintf(clock_desc, sizeof(clock_desc), "unknown");
+ break;
+ case 255:
+ snprintf(clock_desc, sizeof(clock_desc), ">254ns");
+ break;
+ default:
+ snprintf(clock_desc, sizeof(clock_desc), "%uns",
+ dev->ptm_granularity);
+ break;
+ }
+ pci_info(dev, "PTM enabled%s, %s granularity\n",
+ dev->ptm_root ? " (root)" : "", clock_desc);
+
+ return 0;
+}
+EXPORT_SYMBOL(pci_enable_ptm);
+
+static void __pci_disable_ptm(struct pci_dev *dev)
+{
+ u16 ptm = dev->ptm_cap;
+ u32 ctrl;
+
+ if (!ptm)
+ return;
+
+ pci_read_config_dword(dev, ptm + PCI_PTM_CTRL, &ctrl);
+ ctrl &= ~(PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT);
+ pci_write_config_dword(dev, ptm + PCI_PTM_CTRL, ctrl);
+}
+
+/**
+ * pci_disable_ptm() - Disable Precision Time Measurement
+ * @dev: PCI device
+ *
+ * Disable Precision Time Measurement for @dev.
+ */
+void pci_disable_ptm(struct pci_dev *dev)
+{
+ if (dev->ptm_enabled) {
+ __pci_disable_ptm(dev);
+ dev->ptm_enabled = 0;
+ }
+}
+EXPORT_SYMBOL(pci_disable_ptm);
+
+/*
+ * Disable PTM, but preserve dev->ptm_enabled so we silently re-enable it on
+ * resume if necessary.
+ */
+void pci_suspend_ptm(struct pci_dev *dev)
+{
+ if (dev->ptm_enabled)
+ __pci_disable_ptm(dev);
+}
+
+/* If PTM was enabled before suspend, re-enable it when resuming */
+void pci_resume_ptm(struct pci_dev *dev)
+{
+ if (dev->ptm_enabled)
+ __pci_enable_ptm(dev);
+}
+
+bool pcie_ptm_enabled(struct pci_dev *dev)
+{
+ if (!dev)
+ return false;
+
+ return dev->ptm_enabled;
+}
+EXPORT_SYMBOL(pcie_ptm_enabled);