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

From: Shuai Xue <xueshuai@linux.alibaba.com>
To: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
	will@kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, rdunlap@infradead.org,
	robin.murphy@arm.com, mark.rutland@arm.com,
	baolin.wang@linux.alibaba.com, zhuo.song@linux.alibaba.com,
	linux-pci@vger.kernel.org
Subject: Re: [PATCH v1 2/3] drivers/perf: add DesignWare PCIe PMU driver
Date: Tue, 27 Sep 2022 20:29:15 +0800	[thread overview]
Message-ID: <57a0687d-d961-8f8f-8b08-818a07388e49@linux.alibaba.com> (raw)
In-Reply-To: <20220927110435.00005b4d@huawei.com>

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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