linux-kernel - Re: [PATCH 3/4] perf/dwc_pcie: Always register for PCIe bus notifier

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Message-ID: <2d882c88-fd56-c512-0dcc-8825ba920b51@quicinc.com>
Date: Fri, 16 Aug 2024 09:21:33 +0530
From: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To: Yicong Yang <yangyicong@...wei.com>
CC: Shuai Xue <xueshuai@...ux.alibaba.com>,
        Jing Zhang
	<renyu.zj@...ux.alibaba.com>,
        Will Deacon <will@...nel.org>, Mark Rutland
	<mark.rutland@....com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        "Yicong
 Yang" <yangyicong@...ilicon.com>,
        Jonathan Cameron
	<Jonathan.Cameron@...wei.com>,
        Jonathan Corbet <corbet@....net>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <quic_vbadigan@...cinc.com>,
        <quic_nitegupt@...cinc.com>, <quic_skananth@...cinc.com>,
        <quic_ramkri@...cinc.com>, <quic_parass@...cinc.com>,
        <quic_mrana@...cinc.com>
Subject: Re: [PATCH 3/4] perf/dwc_pcie: Always register for PCIe bus notifier



On 8/15/2024 7:19 PM, Yicong Yang wrote:
> On 2024/7/31 12:23, Krishna chaitanya chundru wrote:
>> When the PCIe devices are discovered late, the driver can't find
>> the PCIe devices and returns in the init without registering with
>> the bus notifier. Due to that the devices which are discovered late
>> the driver can't register for this.
>>
>> Register for bus notifier even if the device is not found in init.
>>
>> Fixes: af9597adc2f1 ("drivers/perf: add DesignWare PCIe PMU driver")
>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
>> ---
>>   drivers/perf/dwc_pcie_pmu.c | 10 +++++-----
>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/perf/dwc_pcie_pmu.c b/drivers/perf/dwc_pcie_pmu.c
>> index c115348b8d53..aa1010b44bcb 100644
>> --- a/drivers/perf/dwc_pcie_pmu.c
>> +++ b/drivers/perf/dwc_pcie_pmu.c
>> @@ -741,8 +741,6 @@ static int __init dwc_pcie_pmu_init(void)
>>   
>>   		found = true;
>>   	}
>> -	if (!found)
>> -		return -ENODEV;
>>   
>>   	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
>>   				      "perf/dwc_pcie_pmu:online",
>> @@ -753,9 +751,11 @@ static int __init dwc_pcie_pmu_init(void)
>>   
>>   	dwc_pcie_pmu_hp_state = ret;
>>   
>> -	ret = platform_driver_register(&dwc_pcie_pmu_driver);
>> -	if (ret)
>> -		goto platform_driver_register_err;
>> +	if (!found) {
>> +		ret = platform_driver_register(&dwc_pcie_pmu_driver);
>> +		if (ret)
>> +			goto platform_driver_register_err;
>> +	}
>>
> 
> This doesn't match the commit.
> > If any device is found at this stage, we cannot use them since you don't
> register a driver.
> 
If the device is not found then only we are skipping platform driver
register otherwise driver will be registering with the platform driver.

- Krishna Chaitanya.
>>   	ret = bus_register_notifier(&pci_bus_type, &dwc_pcie_pmu_nb);
>>   	if (ret)
>>