From 8236fc613d44e59f6736d6c3e9efffaf26ab7f00 Mon Sep 17 00:00:00 2001 From: Shuai Xue Date: Wed, 10 Dec 2025 21:29:07 +0800 Subject: [PATCH] Documentation: tracing: Add PCI tracepoint documentation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 [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 Reviewed-by: Ilpo Järvinen Link: https://patch.msgid.link/20251210132907.58799-4-xueshuai@linux.alibaba.com --- Documentation/trace/events-pci.rst | 74 ++++++++++++++++++++++++++++++ Documentation/trace/index.rst | 1 + 2 files changed, 75 insertions(+) create mode 100644 Documentation/trace/events-pci.rst diff --git a/Documentation/trace/events-pci.rst b/Documentation/trace/events-pci.rst new file mode 100644 index 0000000000000..03ff4ad30ddfa --- /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 + + # 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 diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst index b4a429dc4f7ad..0a40bfabcf19b 100644 --- a/Documentation/trace/index.rst +++ b/Documentation/trace/index.rst @@ -54,6 +54,7 @@ applications. events-power events-nmi events-msr + events-pci boottime-trace histogram histogram-design -- 2.47.3