linux-kernel - Re: [External] : [PATCH v13 3/3] Documentation: tracing: Add documentation about PCI tracepoints

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Message-ID: <edf92e08-85d0-4553-9461-625c03b3a5d2@linux.alibaba.com>
Date: Wed, 10 Dec 2025 09:56:53 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: ALOK TIWARI <alok.a.tiwari@...cle.com>, rostedt@...dmis.org,
 lukas@...ner.de, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-edac@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 helgaas@...nel.org, ilpo.jarvinen@...ux.intel.com, mattc@...estorage.com,
 Jonathan.Cameron@...wei.com
Cc: bhelgaas@...gle.com, tony.luck@...el.com, bp@...en8.de,
 mhiramat@...nel.org, mathieu.desnoyers@...icios.com, oleg@...hat.com,
 naveen@...nel.org, davem@...emloft.net, anil.s.keshavamurthy@...el.com,
 mark.rutland@....com, peterz@...radead.org, tianruidong@...ux.alibaba.com
Subject: Re: [External] : [PATCH v13 3/3] Documentation: tracing: Add
 documentation about PCI tracepoints

Hi, Alok,

在 2025/12/9 21:59, ALOK TIWARI 写道:
> 
> 
> On 10/25/2025 5:11 PM, Shuai Xue wrote:
>> 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@...ux.intel.com>
>> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
>> ---
>>   Documentation/trace/events-pci.rst | 74 ++++++++++++++++++++++++++++++
>>   1 file changed, 74 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 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 >"

Good catch.

> 
>> +
>> +    # 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",

Sorry for missing the format.

> 
>> +
>> +**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

I will send a new version to fix above issues.

Thanks.
Shuai