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 000000000..b4e5f5534
--- /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);