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;
}
dev_info(&dev->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);
|
