linux-kernel - Re: [PATCH v1 2/3] drivers/perf: add DesignWare PCIe PMU driver

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Message-ID: <7502d496-9ec1-1ca4-c643-376ec2aa662e@linux.alibaba.com>
Date:   Tue, 27 Sep 2022 13:13:29 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     will@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, rdunlap@...radead.org,
        robin.murphy@....com, mark.rutland@....com,
        baolin.wang@...ux.alibaba.com, zhuo.song@...ux.alibaba.com,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v1 2/3] drivers/perf: add DesignWare PCIe PMU driver



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_200/Rx_PCIe_TLP_Data_Payload/

Bjorn and Jonathan, are you happy with this flow?

Thank you.

Best Regards,
Shuai