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Message-ID: <6e9b4379-5849-73cd-4d89-5e809b4c71a4@quicinc.com>
Date: Mon, 8 Apr 2024 14:32:18 +0530
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Subject: Re: [PATCH v9 6/6] PCI: qcom: Add OPP support to scale performance
 state of power domain
Content-Language: en-US
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
CC: Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio
	<konrad.dybcio@linaro.org>,
        Rob Herring <robh@kernel.org>,
        "Krzysztof
 Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley
	<conor+dt@kernel.org>,
        Lorenzo Pieralisi <lpieralisi@kernel.org>,
        =?UTF-8?Q?Krzysztof_Wilczy=c5=84ski?= <kw@linux.com>,
        Bjorn Helgaas
	<bhelgaas@google.com>, <johan+linaro@kernel.org>,
        <bmasney@redhat.com>, <djakov@kernel.org>,
        <linux-arm-msm@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-pci@vger.kernel.org>,
        <vireshk@kernel.org>, <quic_vbadigan@quicinc.com>,
        <quic_skananth@quicinc.com>, <quic_nitegupt@quicinc.com>,
        <quic_parass@quicinc.com>, <krzysztof.kozlowski@linaro.org>
References: <20240407-opp_support-v9-0-496184dc45d7@quicinc.com>
 <20240407-opp_support-v9-6-496184dc45d7@quicinc.com>
 <20240407150048.GE2679@thinkpad>
From: Krishna Chaitanya Chundru <quic_krichai@quicinc.com>
In-Reply-To: <20240407150048.GE2679@thinkpad>
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On 4/7/2024 8:30 PM, Manivannan Sadhasivam wrote:
> On Sun, Apr 07, 2024 at 10:07:39AM +0530, Krishna chaitanya chundru wrote:
>> QCOM Resource Power Manager-hardened (RPMh) is a hardware block which
>> maintains hardware state of a regulator by performing max aggregation of
>> the requests made by all of the clients.
>>
>> PCIe controller can operate on different RPMh performance state of power
>> domain based on the speed of the link. And this performance state varies
>> from target to target, like some controllers support GEN3 in NOM (Nominal)
>> voltage corner, while some other supports GEN3 in low SVS (static voltage
>> scaling).
>>
>> The SoC can be more power efficient if we scale the performance state
>> based on the aggregate PCIe link bandwidth.
>>
>> Add Operating Performance Points (OPP) support to vote for RPMh state based
>> on the aggregate link bandwidth.
>>
>> OPP can handle ICC bw voting also, so move ICC bw voting through OPP
>> framework if OPP entries are present.
>>
>> Different link configurations may share the same aggregate bandwidth,
>> e.g., a 2.5 GT/s x2 link and a 5.0 GT/s x1 link have the same bandwidth
>> and share the same OPP entry.
>>
> 
> This info should be part of the dts change.
> 
ok I will move this to dts patch in next patch series.
>> As we are moving ICC voting as part of OPP, don't initialize ICC if OPP
>> is supported.
>>
>> Before PCIe link is initialized vote for highest OPP in the OPP table,
>> so that we are voting for maximum voltage corner for the link to come up
>> in maximum supported speed.
>>
>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 72 +++++++++++++++++++++++++++-------
>>   1 file changed, 58 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index b4893214b2d3..4ad5ef3bf8fc 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -22,6 +22,7 @@
>>   #include <linux/of.h>
>>   #include <linux/of_gpio.h>
>>   #include <linux/pci.h>
>> +#include <linux/pm_opp.h>
>>   #include <linux/pm_runtime.h>
>>   #include <linux/platform_device.h>
>>   #include <linux/phy/pcie.h>
>> @@ -1442,15 +1443,13 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>>   	return 0;
>>   }
>>   
>> -static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
>> +static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
>>   {
>>   	struct dw_pcie *pci = pcie->pci;
>> -	u32 offset, status;
>> +	u32 offset, status, freq;
>> +	struct dev_pm_opp *opp;
>>   	int speed, width;
>> -	int ret;
>> -
>> -	if (!pcie->icc_mem)
>> -		return;
>> +	int ret, mbps;
>>   
>>   	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>>   	status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
>> @@ -1462,10 +1461,26 @@ static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
>>   	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
>>   	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, status);
>>   
>> -	ret = icc_set_bw(pcie->icc_mem, 0, width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
>> -	if (ret) {
>> -		dev_err(pci->dev, "failed to set interconnect bandwidth for PCIe-MEM: %d\n",
>> -			ret);
>> +	if (pcie->icc_mem) {
>> +		ret = icc_set_bw(pcie->icc_mem, 0, width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
>> +		if (ret) {
>> +			dev_err(pci->dev, "failed to set interconnect bandwidth for PCIe-MEM: %d\n",
> 
> s/failed/Failed
> 
>> +				ret);
>> +		}
>> +	} else {
>> +		mbps = pcie_link_speed_to_mbps(pcie_link_speed[speed]);
>> +		if (mbps < 0)
>> +			return;
>> +
>> +		freq = mbps * 1000;
>> +		opp = dev_pm_opp_find_freq_exact(pci->dev, freq * width, true);
> 
> As per the API documentation, dev_pm_opp_put() should be called for both success
> and failure case.
> 
ACK.
>> +		if (!IS_ERR(opp)) {
> 
> So what is the action if OPP is not found for the freq?
> 
There is already a vote for maximum freq in the probe, so if it fails
here we can continue here.
If you feel otherwise let me know I Can make changes as suggested.
>> +			ret = dev_pm_opp_set_opp(pci->dev, opp);
>> +			if (ret)
>> +				dev_err(pci->dev, "Failed to set opp: freq %ld ret %d\n",
> 
> 'Failed to set OPP for freq (%ld): %d'
> 
>> +					dev_pm_opp_get_freq(opp), ret);
>> +			dev_pm_opp_put(opp);
>> +		}
>>   	}
>>   }
>>   
>> @@ -1509,8 +1524,10 @@ static void qcom_pcie_init_debugfs(struct qcom_pcie *pcie)
>>   static int qcom_pcie_probe(struct platform_device *pdev)
>>   {
>>   	const struct qcom_pcie_cfg *pcie_cfg;
>> +	unsigned long max_freq = INT_MAX;
>>   	struct device *dev = &pdev->dev;
>>   	struct qcom_pcie *pcie;
>> +	struct dev_pm_opp *opp;
>>   	struct dw_pcie_rp *pp;
>>   	struct resource *res;
>>   	struct dw_pcie *pci;
>> @@ -1577,9 +1594,33 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>>   		goto err_pm_runtime_put;
>>   	}
>>   
>> -	ret = qcom_pcie_icc_init(pcie);
>> -	if (ret)
>> +	/* OPP table is optional */
>> +	ret = devm_pm_opp_of_add_table(dev);
>> +	if (ret && ret != -ENODEV) {
>> +		dev_err_probe(dev, ret, "Failed to add OPP table\n");
>>   		goto err_pm_runtime_put;
>> +	}
>> +
>> +	/*
>> +	 * Use highest OPP here if the OPP table is present. At the end of
> 
> I believe I asked you to add the information justifying why the highest OPP
> should be used.
>
I added the info in the commit message, I will add as the comment in the
next patch.

>> +	 * the probe(), OPP will be updated using qcom_pcie_icc_opp_update().
>> +	 */
>> +	if (!ret) {
>> +		opp = dev_pm_opp_find_freq_floor(dev, &max_freq);
> 
> Same comment as dev_pm_opp_find_freq_exact().
> 
>> +		if (!IS_ERR(opp)) {
>> +			ret = dev_pm_opp_set_opp(dev, opp);
>> +			if (ret)
>> +				dev_err_probe(pci->dev, ret,
>> +					      "Failed to set OPP: freq %ld\n",
> 
> Same comment as above.
> 
>> +					      dev_pm_opp_get_freq(opp));
>> +			dev_pm_opp_put(opp);
> 
> So you want to continue even in the case of failure?
> 
I wil make changes to fallback to driver voting for icc bw if it fails here.
- Krishna chaitanya,
> - Mani
> 
>> +		}
>> +	} else {
>> +		/* Skip ICC init if OPP is supported as it is handled by OPP */
>> +		ret = qcom_pcie_icc_init(pcie);
>> +		if (ret)
>> +			goto err_pm_runtime_put;
>> +	}
>>   
>>   	ret = pcie->cfg->ops->get_resources(pcie);
>>   	if (ret)
>> @@ -1599,7 +1640,7 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>>   		goto err_phy_exit;
>>   	}
>>   
>> -	qcom_pcie_icc_update(pcie);
>> +	qcom_pcie_icc_opp_update(pcie);
>>   
>>   	if (pcie->mhi)
>>   		qcom_pcie_init_debugfs(pcie);
>> @@ -1658,6 +1699,9 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>>   	if (ret)
>>   		dev_err(dev, "failed to disable icc path of CPU-PCIe: %d\n", ret);
>>   
>> +	if (!pcie->icc_mem)
>> +		dev_pm_opp_set_opp(pcie->pci->dev, NULL);
>> +
>>   	return ret;
>>   }
>>   
>> @@ -1680,7 +1724,7 @@ static int qcom_pcie_resume_noirq(struct device *dev)
>>   		pcie->suspended = false;
>>   	}
>>   
>> -	qcom_pcie_icc_update(pcie);
>> +	qcom_pcie_icc_opp_update(pcie);
>>   
>>   	return 0;
>>   }
>>
>> -- 
>> 2.42.0
>>
>