linux-kernel - Re: [PATCH v1 1/3] docs: perf: Add description for Synopsys DesignWare PCIe PMU driver

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Date:   Fri, 23 Sep 2022 22:47:11 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     Yicong Yang <yangyicong@...wei.com>
Cc:     yangyicong@...ilicon.com, will@...nel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Jonathan.Cameron@...wei.com, rdunlap@...radead.org,
        robin.murphy@....com, mark.rutland@....com,
        baolin.wang@...ux.alibaba.com, zhuo.song@...ux.alibaba.com
Subject: Re: [PATCH v1 1/3] docs: perf: Add description for Synopsys
 DesignWare PCIe PMU driver



在 2022/9/23 AM9:27, Yicong Yang 写道:
> On 2022/9/17 20:10, Shuai Xue wrote:
>> Alibaba's T-Head Yitan 710 SoC is built on Synopsys' widely deployed and
>> silicon-proven DesignWare Core PCIe controller which implements PMU for
>> performance and functional debugging to facilitate system maintenance.
>> Document it to provide guidance on how to use it.
>>
>> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
>> ---
>>  .../admin-guide/perf/dwc_pcie_pmu.rst         | 61 +++++++++++++++++++
>>  Documentation/admin-guide/perf/index.rst      |  1 +
>>  2 files changed, 62 insertions(+)
>>  create mode 100644 Documentation/admin-guide/perf/dwc_pcie_pmu.rst
>>
>> diff --git a/Documentation/admin-guide/perf/dwc_pcie_pmu.rst b/Documentation/admin-guide/perf/dwc_pcie_pmu.rst
>> new file mode 100644
>> index 000000000000..fbcbf10b23b7
>> --- /dev/null
>> +++ b/Documentation/admin-guide/perf/dwc_pcie_pmu.rst
>> @@ -0,0 +1,61 @@
>> +======================================================================
>> +Synopsys DesignWare Cores (DWC) PCIe Performance Monitoring Unit (PMU)
>> +======================================================================
>> +
>> +DesignWare Cores (DWC) PCIe PMU
>> +===============================
>> +
>> +To facilitate collection of statistics, Synopsys DesignWare Cores PCIe
>> +controller provides the following two features:
>> +
>> +- Time Based Analysis (RX/TX data throughput and time spent in each
>> +  low-power LTSSM state)
>> +- Lane Event counters (Error and Non-Error for lanes)
>> +
>> +The PMU is not a PCIe Root Complex integrated End Point (RCiEP) device but
>> +only register counters provided by each PCIe Root Port.
>> +
>> +Time Based Analysis
>> +-------------------
>> +
>> +Using this feature you can obtain information regarding RX/TX data
>> +throughput and time spent in each low-power LTSSM state by the controller.
>> +
>> +The counters are 64-bit width and measure data in two categories,
>> +
>> +- percentage of time does the controller stay in LTSSM state in a
>> +  configurable duration. The measurement range of each Event in Group#0.
>> +- amount of data processed (Units of 16 bytes). The measurement range of
>> +  each Event in Group#1.
>> +
>> +Lane Event counters
>> +-------------------
>> +
>> +Using this feature you can obtain Error and Non-Error information in
>> +specific lane by the controller.
>> +
>> +The counters are 32-bit width and the measured event is select by:
>> +
>> +- Group i
>> +- Event j within the Group i
>> +- and Lank k
> 
> Typo here? I guess it's "Lane k"?

Good catch, thank you. Will fix in next version.

Best Regards,
Shuai

> 
>> +
>> +Some of the event counters only exist for specific configurations.
>> +
>> +DesignWare Cores (DWC) PCIe PMU Driver
>> +=======================================
>> +
>> +This driver add PMU devices for each PCIe Root Port. And the PMU device is
>> +named based the BDF of Root Port. For example,
>> +
>> +    10:00.0 PCI bridge: Device 1ded:8000 (rev 01)
>> +
>> +the PMU device name for this Root Port is pcie_bdf_100000.
>> +
>> +Example usage of counting PCIe RX TLP data payload (Units of 16 bytes)::
>> +
>> +    $# perf stat -a -e pcie_bdf_200/Rx_PCIe_TLP_Data_Payload/
>> +
>> +average RX bandwidth can be calculated like this:
>> +
>> +    PCIe TX Bandwidth = PCIE_TX_DATA * 16B / Measure_Time_Window
>> diff --git a/Documentation/admin-guide/perf/index.rst b/Documentation/admin-guide/perf/index.rst
>> index 9c9ece88ce53..8e6a5472aeb3 100644
>> --- a/Documentation/admin-guide/perf/index.rst
>> +++ b/Documentation/admin-guide/perf/index.rst
>> @@ -18,3 +18,4 @@ Performance monitor support
>>     xgene-pmu
>>     arm_dsu_pmu
>>     thunderx2-pmu
>> +   dwc_pcie_pmu
>>