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// SPDX-License-Identifier: GPL-2.0
/*
* PCI Express Precision Time Measurement
* Copyright (c) 2016, Intel Corporation.
*/
#include <linux/bitfield.h>
#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 = FIELD_GET(PCI_PTM_GRANULARITY_MASK, cap);
/*
* 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 |= FIELD_PREP(PCI_PTM_GRANULARITY_MASK, dev->ptm_granularity);
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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