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- // 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);
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