Messages in this thread | | | Date | Mon, 7 Nov 2022 15:28:10 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v1 1/3] docs: perf: Add description for Synopsys DesignWare PCIe PMU driver |
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On Fri, Sep 23, 2022 at 09:51:40PM +0800, Shuai Xue wrote: > > > 在 2022/9/22 PM9:25, Will Deacon 写道: > > On Sat, Sep 17, 2022 at 08:10:34PM +0800, 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@linux.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 > >> + > >> +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/ > > > > Do you really need to expose a separate PMU instance to userspace for each > > BDF? I think it would be much cleaner if you could follow the approach used > > by hisilicon/hisi_pcie_pmu.c and hide these details in the driver, exposing > > a `bdf=' selector to userspace instead. > > Thank you for your valuable comments. > > It's a good idea to encode bdf in bitmap and exposing a `bdf=' selector to userspace. > The problem of bdf selector is that the user need to compute bdf from lanes, do you > think it is user friendly? I'm worried about increasing the burden of users.
I don't see this as being an issue, particularly if you document how to do it.
Will
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