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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 | // 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"
static void pci_ptm_info(struct pci_dev *dev)
{
char clock_desc[8];
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), "%udns",
dev->ptm_granularity);
break;
}
pci_info(dev, "PTM enabled%s, %s granularity\n",
dev->ptm_root ? " (root)" : "", clock_desc);
}
void pci_ptm_init(struct pci_dev *dev)
{
int pos;
u32 cap, ctrl;
u8 local_clock;
struct pci_dev *ups;
if (!pci_is_pcie(dev))
return;
pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);
if (!pos)
return;
/*
* Enable PTM only on interior devices (root ports, switch ports,
* etc.) on the assumption that it causes no link traffic until an
* endpoint enables it.
*/
if ((pci_pcie_type(dev) == PCI_EXP_TYPE_ENDPOINT ||
pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END))
return;
pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
local_clock = (cap & PCI_PTM_GRANULARITY_MASK) >> 8;
/*
* There's no point in enabling PTM unless it's enabled in the
* upstream device or this device can be a PTM Root itself. Per
* the spec recommendation (PCIe r3.1, sec 7.32.3), select the
* furthest upstream Time Source as the PTM Root.
*/
ups = pci_upstream_bridge(dev);
if (ups && ups->ptm_enabled) {
ctrl = PCI_PTM_CTRL_ENABLE;
if (ups->ptm_granularity == 0)
dev->ptm_granularity = 0;
else if (ups->ptm_granularity > local_clock)
dev->ptm_granularity = ups->ptm_granularity;
} else {
if (cap & PCI_PTM_CAP_ROOT) {
ctrl = PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT;
dev->ptm_root = 1;
dev->ptm_granularity = local_clock;
} else
return;
}
ctrl |= dev->ptm_granularity << 8;
pci_write_config_dword(dev, pos + PCI_PTM_CTRL, ctrl);
dev->ptm_enabled = 1;
pci_ptm_info(dev);
}
int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
{
int pos;
u32 cap, ctrl;
struct pci_dev *ups;
if (!pci_is_pcie(dev))
return -EINVAL;
pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);
if (!pos)
return -EINVAL;
pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
if (!(cap & PCI_PTM_CAP_REQ))
return -EINVAL;
/*
* For a PCIe Endpoint, PTM is only useful if the endpoint can
* issue PTM requests to upstream devices that have PTM enabled.
*
* For Root Complex Integrated Endpoints, there is no upstream
* device, so there must be some implementation-specific way to
* associate the endpoint with a time source.
*/
if (pci_pcie_type(dev) == PCI_EXP_TYPE_ENDPOINT) {
ups = pci_upstream_bridge(dev);
if (!ups || !ups->ptm_enabled)
return -EINVAL;
dev->ptm_granularity = ups->ptm_granularity;
} else if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
dev->ptm_granularity = 0;
} else
return -EINVAL;
ctrl = PCI_PTM_CTRL_ENABLE;
ctrl |= dev->ptm_granularity << 8;
pci_write_config_dword(dev, pos + PCI_PTM_CTRL, ctrl);
dev->ptm_enabled = 1;
pci_ptm_info(dev);
if (granularity)
*granularity = dev->ptm_granularity;
return 0;
}
EXPORT_SYMBOL(pci_enable_ptm);
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