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.. SPDX-License-Identifier: GPL-2.0
===========================
Subsystem Trace Points: PCI
===========================
Overview
========
The PCI tracing system provides tracepoints to monitor critical hardware events
that can impact system performance and reliability. These events normally show
up here:
/sys/kernel/tracing/events/pci
Cf. include/trace/events/pci.h for the events definitions.
Available Tracepoints
=====================
pci_hp_event
------------
Monitors PCI hotplug events including card insertion/removal and link
state changes.
::
pci_hp_event "%s slot:%s, event:%s\n"
**Event Types**:
* ``LINK_UP`` - PCIe link established
* ``LINK_DOWN`` - PCIe link lost
* ``CARD_PRESENT`` - Card detected in slot
* ``CARD_NOT_PRESENT`` - Card removed from slot
**Example Usage**::
# Enable the tracepoint
echo 1 > /sys/kernel/debug/tracing/events/pci/pci_hp_event/enable
# Monitor events (the following output is generated when a device is hotplugged)
cat /sys/kernel/debug/tracing/trace_pipe
irq/51-pciehp-88 [001] ..... 1311.177459: pci_hp_event: 0000:00:02.0 slot:10, event:CARD_PRESENT
irq/51-pciehp-88 [001] ..... 1311.177566: pci_hp_event: 0000:00:02.0 slot:10, event:LINK_UP
pcie_link_event
---------------
Monitors PCIe link speed changes and provides detailed link status information.
::
pcie_link_event "%s type:%d, reason:%d, cur_bus_speed:%d, max_bus_speed:%d, width:%u, flit_mode:%u, status:%s\n"
**Parameters**:
* ``type`` - PCIe device type (4=Root Port, etc.)
* ``reason`` - Reason for link change:
- ``0`` - Link retrain
- ``1`` - Bus enumeration
- ``2`` - Bandwidth notification enable
- ``3`` - Bandwidth notification IRQ
- ``4`` - Hotplug event
**Example Usage**::
# Enable the tracepoint
echo 1 > /sys/kernel/debug/tracing/events/pci/pcie_link_event/enable
# Monitor events (the following output is generated when a device is hotplugged)
cat /sys/kernel/debug/tracing/trace_pipe
irq/51-pciehp-88 [001] ..... 381.545386: pcie_link_event: 0000:00:02.0 type:4, reason:4, cur_bus_speed:20, max_bus_speed:23, width:1, flit_mode:0, status:DLLLA
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