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    SubjectRe: [PATCH v1 2/3] drivers/perf: add DesignWare PCIe PMU driver
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    在 2022/9/27 PM6:04, Jonathan Cameron 写道:
    > On Tue, 27 Sep 2022 13:13:29 +0800
    > Shuai Xue <xueshuai@linux.alibaba.com> wrote:
    >
    >> 在 2022/9/27 AM1:18, Bjorn Helgaas 写道:
    >>> On Mon, Sep 26, 2022 at 09:31:34PM +0800, Shuai Xue wrote:
    >>>> 在 2022/9/23 PM11:54, Jonathan Cameron 写道:
    >>>>>> I found a similar definition in arch/ia64/pci/pci.c .
    >>>>>>
    >>>>>> #define PCI_SAL_ADDRESS(seg, bus, devfn, reg) \
    >>>>>> (((u64) seg << 24) | (bus << 16) | (devfn << 8) | (reg))
    >>>>>>
    >>>>>> Should we move it into a common header first?
    >>>>>
    >>>>> Maybe. The bus, devfn, reg part is standard bdf, but I don't think
    >>>>> the PCI 6.0 spec defined a version with the seg in the upper bits.
    >>>>> I'm not sure if we want to adopt that in LInux.
    >>>>
    >>>> I found lots of code use seg,bus,devfn,reg with format "%04x:%02x:%02x.%x",
    >>>> I am not quite familiar with PCIe spec. What do you think about it, Bjorn?
    >>>
    >>> The PCIe spec defines an address encoding for bus/device/function/reg
    >>> for the purposes of ECAM (PCIe r6.0, sec 7.2.2), but as far as I know,
    >>> it doesn't define anything similar that includes the segment. The
    >>> segment is really outside the scope of PCIe because each segment is a
    >>> completely separate PCIe hierarchy.
    >>
    >> Thank you for your explanation.
    >>
    >>>
    >>> So I probably wouldn't make this a generic definition. But if/when
    >>> you print things like this out, please do use the format spec you
    >>> mentioned above so it matches the style used elsewhere.
    >>>
    >>
    >> Agree. The print format of bus/device/function/reg is "%04x:%02x:%02x.%x",
    >> so I named the PMU as the same format. Then the usage flow would be:
    >>
    >> - lspci to get the device root port in format seg/bus/device/function/reg.
    >> 10:00.0 PCI bridge: Device 1ded:8000 (rev 01)
    >> - select its PMU name pcie_bdf_100000.
    >> - monitor with perf:
    >> perf stat -a -e pcie_bdf_100000/Rx_PCIe_TLP_Data_Payload/
    >
    > I think you probably want something in there to indicate it's an RP
    > and the bdf part may be redundant...

    Yes, I realized that the prefix `pcie_bdf` is not appropriate. Let's discuss
    with Robin in his thread.

    Thank you.

    Best Regards,
    Shuai

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