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

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Message-ID: <cf6ec52e-61ad-f76d-02fd-831c63e35d40@quicinc.com>
Date: Tue, 16 Jan 2024 10:36:23 +0530
From: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To: Bjorn Helgaas <helgaas@...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 10:17 PM, Bjorn Helgaas wrote:
> Capitalize "ICC" and "CPU" to make the subject easier to read.
> "Missing" might be superfluous in the subject?  It would be nice to
> have the ICC expansion once in the commit log as a hook for newbies
> like me :)
> 
Sure I will change a suggested in next patch series.
> 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.
>> As there is less access on this path compared to pcie to mem path
>> add minimum vote i.e GEN1x1 bandwidth always.
> 
> "GEN1x1" is unnecessarily ambiguous, and the spec recommends avoiding
> it (PCIe r6.0, sec 1.2).  Use the actual bandwidth numbers instead.
> 
> "PCIe" to match above.  Also below in comments and messages.
> 
ACK.
>> In suspend remove the cpu vote after register space access is done.
> 
> "CPU" to match above.
> 
ACK
>> Fixes: c4860af88d0c ("PCI: qcom: Add basic interconnect support")
>> cc: stable@...r.kernel.org
>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 31 +++++++++++++++++++++++++++++--
>>   1 file changed, 29 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index 11c80555d975..035953f0b6d8 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -240,6 +240,7 @@ struct qcom_pcie {
>>   	struct phy *phy;
>>   	struct gpio_desc *reset;
>>   	struct icc_path *icc_mem;
>> +	struct icc_path *icc_cpu;
>>   	const struct qcom_pcie_cfg *cfg;
>>   	struct dentry *debugfs;
>>   	bool suspended;
>> @@ -1372,6 +1373,9 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>>   	if (IS_ERR(pcie->icc_mem))
>>   		return PTR_ERR(pcie->icc_mem);
>>   
>> +	pcie->icc_cpu = devm_of_icc_get(pci->dev, "cpu-pcie");
>> +	if (IS_ERR(pcie->icc_cpu))
>> +		return PTR_ERR(pcie->icc_cpu);
>>   	/*
>>   	 * Some Qualcomm platforms require interconnect bandwidth constraints
>>   	 * to be set before enabling interconnect clocks.
>> @@ -1381,7 +1385,18 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>>   	 */
>>   	ret = icc_set_bw(pcie->icc_mem, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
>>   	if (ret) {
>> -		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
>> +		dev_err(pci->dev, "failed to set interconnect bandwidth for pcie-mem: %d\n",
>> +			ret);
>> +		return ret;
>> +	}
>> +
>> +	/*
>> +	 * The config space, BAR space and registers goes through cpu-pcie path.
>> +	 * Set peak bandwidth to single-lane Gen1 for this path all the time.
> 
> Numbers instead of "Gen1".
> 
ACK

-Krishna Chaitanya.
>> +	 */
>> +	ret = icc_set_bw(pcie->icc_cpu, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
>> +	if (ret) {
>> +		dev_err(pci->dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n",
>>   			ret);
>>   		return ret;
>>   	}
>> @@ -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);
>> +	if (ret) {
>> +		dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
>> +		return ret;
>> +	}
>>   	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));
>> +	if (ret) {
>> +		dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>>   	if (pcie->suspended) {
>>   		ret = qcom_pcie_host_init(&pcie->pci->pp);
>>   		if (ret)
>>
>> -- 
>> 2.42.0
>>