linux-kernel - Re: [PATCH v7 3/4] drivers/perf: add DesignWare PCIe PMU driver

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Message-ID: <83e7bb45-7776-4cfa-a3ed-050faaa1e72c@linux.alibaba.com>
Date:   Tue, 17 Oct 2023 08:48:17 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     chengyou@...ux.alibaba.com, kaishen@...ux.alibaba.com,
        yangyicong@...wei.com, will@...nel.org,
        Jonathan.Cameron@...wei.com, baolin.wang@...ux.alibaba.com,
        robin.murphy@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
        rdunlap@...radead.org, mark.rutland@....com,
        zhuo.song@...ux.alibaba.com, renyu.zj@...ux.alibaba.com
Subject: Re: [PATCH v7 3/4] drivers/perf: add DesignWare PCIe PMU driver



On 2023/10/16 22:38, Bjorn Helgaas wrote:
> On Mon, Oct 16, 2023 at 11:00:13AM +0800, Shuai Xue wrote:
>> On 2023/10/14 00:30, Bjorn Helgaas wrote:
>>> On Fri, Oct 13, 2023 at 11:46:44AM +0800, Shuai Xue wrote:
>>>> On 2023/10/13 00:25, Bjorn Helgaas wrote:
>>>>> On Thu, Oct 12, 2023 at 11:28:55AM +0800, Shuai Xue wrote:
>>>>>> This commit adds the PCIe Performance Monitoring Unit (PMU)
>>>>>> driver support for T-Head Yitian SoC chip. Yitian is based on
>>>>>> the Synopsys PCI Express Core controller IP which provides
>>>>>> statistics feature. The PMU is not a PCIe Root Complex
>>>>>> integrated End Point(RCiEP) device but only register counters
>>>>>> provided by each PCIe Root Port.
> 
>> @@ -447,10 +447,10 @@ static int dwc_pcie_pmu_event_add(struct perf_event *event, int flags)
>>  	u32 ctrl;
>>
>>  	/* Only one counter and it is in use */
>> -	if (pcie_pmu->event)
>> +	if (pcie_pmu->event[type])
>>  		return -ENOSPC;
>>
>> -	pcie_pmu->event = event;
>> +	pcie_pmu->event[type] = event;
> 
> OK, makes good sense (probably update the comment also, e.g., "one
> counter of each type").

Yes, will do that.

> 
>>  }
>>> If so, I might word this as:
>>>
>>>   Each Root Port contains one counter that can be used for either:
>>>
>>>     - Time-Based Analysis (RX/TX data throughput and time spent in
>>>       each low-power LTSSM state) or
>>>
>>>     - Event counting (error and non-error events for a specified lane)
>>>
>>>   There is no interrupt for counter overflow.
>>
>> Based on above, I change the word to:
>>
>> 	To facilitate collection of statistics the controller provides the
>> 	following two features for each Root Port:
>>
>> 	- one 64-bit counter for Time Based Analysis (RX/TX data throughput and
>> 	  time spent in each low-power LTSSM state) and
>> 	- one 32-bit counter for Event counting (error and non-error events for
>> 	  a specified lane)
>>
>> 	Note: There is no interrupt for counter overflow.
> 
> Beautiful, that's very clear.
> 

Thank you for quick feedback. I will send a new version latter.

Best Regards.
Shuai