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// SPDX-License-Identifier: GPL-2.0+
/*
* PCI Express Link Bandwidth Notification services driver
* Author: Alexandru Gagniuc <mr.nuke.me@gmail.com>
*
* Copyright (C) 2019, Dell Inc
*
* The PCIe Link Bandwidth Notification provides a way to notify the
* operating system when the link width or data rate changes. This
* capability is required for all root ports and downstream ports
* supporting links wider than x1 and/or multiple link speeds.
*
* This service port driver hooks into the bandwidth notification interrupt
* and warns when links become degraded in operation.
*/
#include "../pci.h"
#include "portdrv.h"
static bool pcie_link_bandwidth_notification_supported(struct pci_dev *dev)
{
int ret;
u32 lnk_cap;
ret = pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnk_cap);
return (ret == PCIBIOS_SUCCESSFUL) && (lnk_cap & PCI_EXP_LNKCAP_LBNC);
}
static void pcie_enable_link_bandwidth_notification(struct pci_dev *dev)
{
u16 lnk_ctl;
pcie_capability_write_word(dev, PCI_EXP_LNKSTA, PCI_EXP_LNKSTA_LBMS);
pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &lnk_ctl);
lnk_ctl |= PCI_EXP_LNKCTL_LBMIE;
pcie_capability_write_word(dev, PCI_EXP_LNKCTL, lnk_ctl);
}
static void pcie_disable_link_bandwidth_notification(struct pci_dev *dev)
{
u16 lnk_ctl;
pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &lnk_ctl);
lnk_ctl &= ~PCI_EXP_LNKCTL_LBMIE;
pcie_capability_write_word(dev, PCI_EXP_LNKCTL, lnk_ctl);
}
static irqreturn_t pcie_bw_notification_irq(int irq, void *context)
{
struct pcie_device *srv = context;
struct pci_dev *port = srv->port;
u16 link_status, events;
int ret;
ret = pcie_capability_read_word(port, PCI_EXP_LNKSTA, &link_status);
events = link_status & PCI_EXP_LNKSTA_LBMS;
if (ret != PCIBIOS_SUCCESSFUL || !events)
return IRQ_NONE;
pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
pcie_update_link_speed(port->subordinate, link_status);
return IRQ_WAKE_THREAD;
}
static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
{
struct pcie_device *srv = context;
struct pci_dev *port = srv->port;
struct pci_dev *dev;
/*
* Print status from downstream devices, not this root port or
* downstream switch port.
*/
down_read(&pci_bus_sem);
list_for_each_entry(dev, &port->subordinate->devices, bus_list)
pcie_report_downtraining(dev);
up_read(&pci_bus_sem);
return IRQ_HANDLED;
}
static int pcie_bandwidth_notification_probe(struct pcie_device *srv)
{
int ret;
/* Single-width or single-speed ports do not have to support this. */
if (!pcie_link_bandwidth_notification_supported(srv->port))
return -ENODEV;
ret = request_threaded_irq(srv->irq, pcie_bw_notification_irq,
pcie_bw_notification_handler,
IRQF_SHARED, "PCIe BW notif", srv);
if (ret)
return ret;
pcie_enable_link_bandwidth_notification(srv->port);
return 0;
}
static void pcie_bandwidth_notification_remove(struct pcie_device *srv)
{
pcie_disable_link_bandwidth_notification(srv->port);
free_irq(srv->irq, srv);
}
static struct pcie_port_service_driver pcie_bandwidth_notification_driver = {
.name = "pcie_bw_notification",
.port_type = PCIE_ANY_PORT,
.service = PCIE_PORT_SERVICE_BWNOTIF,
.probe = pcie_bandwidth_notification_probe,
.remove = pcie_bandwidth_notification_remove,
};
int __init pcie_bandwidth_notification_init(void)
{
return pcie_port_service_register(&pcie_bandwidth_notification_driver);
}
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