1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * PCI Express Link Bandwidth Notification services driver
4 * Author: Alexandru Gagniuc <mr.nuke.me@gmail.com>
5 *
6 * Copyright (C) 2019, Dell Inc
7 *
8 * The PCIe Link Bandwidth Notification provides a way to notify the
9 * operating system when the link width or data rate changes. This
10 * capability is required for all root ports and downstream ports
11 * supporting links wider than x1 and/or multiple link speeds.
12 *
13 * This service port driver hooks into the bandwidth notification interrupt
14 * and warns when links become degraded in operation.
15 */
16
17 #include "../pci.h"
18 #include "portdrv.h"
19
pcie_link_bandwidth_notification_supported(struct pci_dev * dev)20 static bool pcie_link_bandwidth_notification_supported(struct pci_dev *dev)
21 {
22 int ret;
23 u32 lnk_cap;
24
25 ret = pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnk_cap);
26 return (ret == PCIBIOS_SUCCESSFUL) && (lnk_cap & PCI_EXP_LNKCAP_LBNC);
27 }
28
pcie_enable_link_bandwidth_notification(struct pci_dev * dev)29 static void pcie_enable_link_bandwidth_notification(struct pci_dev *dev)
30 {
31 u16 lnk_ctl;
32
33 pcie_capability_write_word(dev, PCI_EXP_LNKSTA, PCI_EXP_LNKSTA_LBMS);
34
35 pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &lnk_ctl);
36 lnk_ctl |= PCI_EXP_LNKCTL_LBMIE;
37 pcie_capability_write_word(dev, PCI_EXP_LNKCTL, lnk_ctl);
38 }
39
pcie_disable_link_bandwidth_notification(struct pci_dev * dev)40 static void pcie_disable_link_bandwidth_notification(struct pci_dev *dev)
41 {
42 u16 lnk_ctl;
43
44 pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &lnk_ctl);
45 lnk_ctl &= ~PCI_EXP_LNKCTL_LBMIE;
46 pcie_capability_write_word(dev, PCI_EXP_LNKCTL, lnk_ctl);
47 }
48
pcie_bw_notification_irq(int irq,void * context)49 static irqreturn_t pcie_bw_notification_irq(int irq, void *context)
50 {
51 struct pcie_device *srv = context;
52 struct pci_dev *port = srv->port;
53 u16 link_status, events;
54 int ret;
55
56 ret = pcie_capability_read_word(port, PCI_EXP_LNKSTA, &link_status);
57 events = link_status & PCI_EXP_LNKSTA_LBMS;
58
59 if (ret != PCIBIOS_SUCCESSFUL || !events)
60 return IRQ_NONE;
61
62 pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
63 pcie_update_link_speed(port->subordinate, link_status);
64 return IRQ_WAKE_THREAD;
65 }
66
pcie_bw_notification_handler(int irq,void * context)67 static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
68 {
69 struct pcie_device *srv = context;
70 struct pci_dev *port = srv->port;
71 struct pci_dev *dev;
72
73 /*
74 * Print status from downstream devices, not this root port or
75 * downstream switch port.
76 */
77 down_read(&pci_bus_sem);
78 list_for_each_entry(dev, &port->subordinate->devices, bus_list)
79 pcie_report_downtraining(dev);
80 up_read(&pci_bus_sem);
81
82 return IRQ_HANDLED;
83 }
84
pcie_bandwidth_notification_probe(struct pcie_device * srv)85 static int pcie_bandwidth_notification_probe(struct pcie_device *srv)
86 {
87 int ret;
88
89 /* Single-width or single-speed ports do not have to support this. */
90 if (!pcie_link_bandwidth_notification_supported(srv->port))
91 return -ENODEV;
92
93 ret = request_threaded_irq(srv->irq, pcie_bw_notification_irq,
94 pcie_bw_notification_handler,
95 IRQF_SHARED, "PCIe BW notif", srv);
96 if (ret)
97 return ret;
98
99 pcie_enable_link_bandwidth_notification(srv->port);
100
101 return 0;
102 }
103
pcie_bandwidth_notification_remove(struct pcie_device * srv)104 static void pcie_bandwidth_notification_remove(struct pcie_device *srv)
105 {
106 pcie_disable_link_bandwidth_notification(srv->port);
107 free_irq(srv->irq, srv);
108 }
109
pcie_bandwidth_notification_suspend(struct pcie_device * srv)110 static int pcie_bandwidth_notification_suspend(struct pcie_device *srv)
111 {
112 pcie_disable_link_bandwidth_notification(srv->port);
113 return 0;
114 }
115
pcie_bandwidth_notification_resume(struct pcie_device * srv)116 static int pcie_bandwidth_notification_resume(struct pcie_device *srv)
117 {
118 pcie_enable_link_bandwidth_notification(srv->port);
119 return 0;
120 }
121
122 static struct pcie_port_service_driver pcie_bandwidth_notification_driver = {
123 .name = "pcie_bw_notification",
124 .port_type = PCIE_ANY_PORT,
125 .service = PCIE_PORT_SERVICE_BWNOTIF,
126 .probe = pcie_bandwidth_notification_probe,
127 .suspend = pcie_bandwidth_notification_suspend,
128 .resume = pcie_bandwidth_notification_resume,
129 .remove = pcie_bandwidth_notification_remove,
130 };
131
pcie_bandwidth_notification_init(void)132 int __init pcie_bandwidth_notification_init(void)
133 {
134 return pcie_port_service_register(&pcie_bandwidth_notification_driver);
135 }
136