LXR linux/drivers/pci/pcie/bw

   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
  20static 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
  29static 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
  40static 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
  49static 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
  67static 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
  85static 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
 104static 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
 110static int pcie_bandwidth_notification_suspend(struct pcie_device *srv)
 111{
 112        pcie_disable_link_bandwidth_notification(srv->port);
 113        return 0;
 114}
 115
 116static int pcie_bandwidth_notification_resume(struct pcie_device *srv)
 117{
 118        pcie_enable_link_bandwidth_notification(srv->port);
 119        return 0;
 120}
 121
 122static 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
 132int __init pcie_bandwidth_notification_init(void)
 133{
 134        return pcie_port_service_register(&pcie_bandwidth_notification_driver);
 135}
 136