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The PCI tracing system provides tracepoints to monitor critical hardware events that can impact system performance and reliability. Add documentation about it. Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com> [bhelgaas: squash fixes: https://lore.kernel.org/r/20260108013956.14351-2-bagasdotme@gmail.com https://lore.kernel.org/r/20260108013956.14351-3-bagasdotme@gmail.com] Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://patch.msgid.link/20251210132907.58799-4-xueshuai@linux.alibaba.com
74 lines
2.1 KiB
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74 lines
2.1 KiB
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.. SPDX-License-Identifier: GPL-2.0
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===========================
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Subsystem Trace Points: PCI
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===========================
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Overview
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========
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The PCI tracing system provides tracepoints to monitor critical hardware events
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that can impact system performance and reliability. These events normally show
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up here:
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/sys/kernel/tracing/events/pci
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Cf. include/trace/events/pci.h for the events definitions.
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Available Tracepoints
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=====================
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pci_hp_event
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------------
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Monitors PCI hotplug events including card insertion/removal and link
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state changes.
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::
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pci_hp_event "%s slot:%s, event:%s\n"
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**Event Types**:
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* ``LINK_UP`` - PCIe link established
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* ``LINK_DOWN`` - PCIe link lost
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* ``CARD_PRESENT`` - Card detected in slot
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* ``CARD_NOT_PRESENT`` - Card removed from slot
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**Example Usage**::
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# Enable the tracepoint
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echo 1 > /sys/kernel/debug/tracing/events/pci/pci_hp_event/enable
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# Monitor events (the following output is generated when a device is hotplugged)
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cat /sys/kernel/debug/tracing/trace_pipe
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irq/51-pciehp-88 [001] ..... 1311.177459: pci_hp_event: 0000:00:02.0 slot:10, event:CARD_PRESENT
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irq/51-pciehp-88 [001] ..... 1311.177566: pci_hp_event: 0000:00:02.0 slot:10, event:LINK_UP
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pcie_link_event
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---------------
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Monitors PCIe link speed changes and provides detailed link status information.
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::
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pcie_link_event "%s type:%d, reason:%d, cur_bus_speed:%d, max_bus_speed:%d, width:%u, flit_mode:%u, status:%s\n"
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**Parameters**:
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* ``type`` - PCIe device type (4=Root Port, etc.)
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* ``reason`` - Reason for link change:
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- ``0`` - Link retrain
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- ``1`` - Bus enumeration
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- ``2`` - Bandwidth notification enable
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- ``3`` - Bandwidth notification IRQ
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- ``4`` - Hotplug event
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**Example Usage**::
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# Enable the tracepoint
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echo 1 > /sys/kernel/debug/tracing/events/pci/pcie_link_event/enable
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# Monitor events (the following output is generated when a device is hotplugged)
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cat /sys/kernel/debug/tracing/trace_pipe
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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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