linux-kernel - Re: [PATCH v6 3/6] PCI: qcom: Add missing icc bandwidth vote for cpu to PCIe path

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Date: Tue, 16 Jan 2024 10:34:22 +0530
From: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To: Johan Hovold <johan@...nel.org>
CC: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio
	<konrad.dybcio@...aro.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Lorenzo
 Pieralisi" <lpieralisi@...nel.org>,
        Krzysztof Wilczyński
	<kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        Brian Masney <bmasney@...hat.com>, Georgi Djakov <djakov@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <vireshk@...nel.org>,
        <quic_vbadigan@...cinc.com>, <quic_skananth@...cinc.com>,
        <quic_nitegupt@...cinc.com>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v6 3/6] PCI: qcom: Add missing icc bandwidth vote for cpu
 to PCIe path



On 1/12/2024 9:29 PM, Johan Hovold wrote:
> On Fri, Jan 12, 2024 at 07:52:02PM +0530, Krishna chaitanya chundru wrote:
>> CPU-PCIe path consits for registers PCIe BAR space, config space.
> 
> consits?
> 
>> As there is less access on this path compared to pcie to mem path
>> add minimum vote i.e GEN1x1 bandwidth always.
> 
> gen1 bandwidth can't be right.
> 
There is no recommended value we need vote for this path, as there is
BAR and config space in this path we are voting for GEN1x1.
Please suggest a recommended value for this path if the GEN1x1 is high.
>> In suspend remove the cpu vote after register space access is done.
>>
>> Fixes: c4860af88d0c ("PCI: qcom: Add basic interconnect support")
>> cc: stable@...r.kernel.org
> 
> This does not look like a fix so drop the above.
> 
> The commit you refer to explicitly left this path unconfigured for now
> and only added support for the configuring the mem path as needed on
> sc8280xp which otherwise would crash.
> 
Without this path vote BAR and config space can result NOC timeout
errors, we are surviving because of other driver vote for this path.
For that reason we added a fix tag.
>> @@ -1573,7 +1588,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>>   	 */
>>   	ret = icc_set_bw(pcie->icc_mem, 0, kBps_to_icc(1));
>>   	if (ret) {
>> -		dev_err(dev, "Failed to set interconnect bandwidth: %d\n", ret);
>> +		dev_err(dev, "Failed to set interconnect bandwidth for pcie-mem: %d\n", ret);
>>   		return ret;
>>   	}
>>   
>> @@ -1597,6 +1612,12 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>>   		pcie->suspended = true;
>>   	}
>>   
>> +	/* Remove cpu path vote after all the register access is done */
>> +	ret = icc_set_bw(pcie->icc_cpu, 0, 0);
> 
> I believe you should use icc_disable() here.
> 
>> +	if (ret) {
>> +		dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
>> +		return ret;
> 
> And you need to unwind before returning on errors.
> 
>> +	}
>>   	return 0;
>>   }
>>   
>> @@ -1605,6 +1626,12 @@ static int qcom_pcie_resume_noirq(struct device *dev)
>>   	struct qcom_pcie *pcie = dev_get_drvdata(dev);
>>   	int ret;
>>   
>> +	ret = icc_set_bw(pcie->icc_cpu, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
> 
> icc_enable()
> 
I was not aware of these API's, I will add them in next patch.

- Krishna Chaitanya.
>> +	if (ret) {
>> +		dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
>> +		return ret;
>> +	}
> 
> Johan