diff options
Diffstat (limited to 'drivers/pci/pcie/ptm.c')
| -rw-r--r-- | drivers/pci/pcie/ptm.c | 253 |
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); |