Re: [External] : [PATCH v13 3/3] Documentation: tracing: Add documentation about PCI tracepoints
From: ALOK TIWARI <hidden>
Date: 2025-12-09 14:00:07
Also in:
linux-edac, linux-pci, lkml
On 10/25/2025 5:11 PM, Shuai Xue wrote:
quoted hunk ↗ jump to hunk
The PCI tracing system provides tracepoints to monitor critical hardware events that can impact system performance and reliability. Add documentation about it. Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com> --- Documentation/trace/events-pci.rst | 74 ++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 Documentation/trace/events-pci.rstdiff --git a/Documentation/trace/events-pci.rst b/Documentation/trace/events-pci.rst new file mode 100644 index 000000000000..88bd38fcc184 --- /dev/null +++ b/Documentation/trace/events-pci.rst@@ -0,0 +1,74 @@ +.. 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
missing space echo 1 >"
+ + # 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:%s, max_bus_speed:%s, width:%u, flit_mode:%u, status:%s\n"
%s -> %d mismatch for cur_bus_speed and max_bus_speed
TP_printk("%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 + echo1 > /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
Thanks, Alok