linux-kernel - Re: [PATCH v3 3/3] PCI: qcom: Add OPP support for speed based performance state of RPMH

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Message-ID: <162b135d-7e27-bf3b-df8f-45e2a5e73897@quicinc.com>
Date:   Tue, 22 Aug 2023 09:57:41 +0530
From:   Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To:     Pavan Kondeti <quic_pkondeti@...cinc.com>
CC:     <manivannan.sadhasivam@...aro.org>, <helgaas@...nel.org>,
        <linux-pci@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_vbadigan@...cinc.com>,
        <quic_nitegupt@...cinc.com>, <quic_skananth@...cinc.com>,
        <quic_ramkri@...cinc.com>, <quic_parass@...cinc.com>,
        <krzysztof.kozlowski@...aro.org>, Andy Gross <agross@...nel.org>,
        "Bjorn Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v3 3/3] PCI: qcom: Add OPP support for speed based
 performance state of RPMH


On 8/22/2023 9:33 AM, Pavan Kondeti wrote:
> On Mon, Aug 21, 2023 at 07:45:43PM +0530, Krishna chaitanya chundru wrote:
>> Before link training vote for the maximum performance state of RPMH
>> and once link is up, vote for the performance state based upon the link
>> speed.
>>
>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 47 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 47 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index 7a87a47..c57ca1a 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -22,6 +22,7 @@
>>   #include <linux/of_device.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>
>> @@ -1357,6 +1358,32 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>>   	return 0;
>>   }
>>   
>> +static void qcom_pcie_opp_update(struct qcom_pcie *pcie)
>> +{
>> +	struct dw_pcie *pci = pcie->pci;
>> +	struct dev_pm_opp *opp;
>> +	u32 offset, status;
>> +	int speed, ret = 0;
>> +
>> +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>> +	status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
>> +
>> +	/* Only update constraints if link is up. */
>> +	if (!(status & PCI_EXP_LNKSTA_DLLLA))
>> +		return;
>> +
> What happens if link is not up during probe? We set max vote before
> this, should not we bring it down in suspend and vote it back again in
> resume?

ok, I will set to lower value in the suspend path if the link is not 
up.  If the link is already up driver will not

do any modifications.

>
>> +	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
>> +
>> +	opp = dev_pm_opp_find_level_exact(pci->dev, speed);
>> +	if (!IS_ERR(opp)) {
>> +		ret = dev_pm_opp_set_opp(pci->dev, opp);
>> +		if (ret)
>> +			dev_err(pci->dev, "Failed to set opp: %d\n", ret);
>> +		dev_pm_opp_put(opp);
>> +	}
> Since you added an error message, make it more useful by printing the
> opp level also. dev_pm_opp_get_level().
Sure I will add this in next patch.
>
>> +
>> +}
>> +
>>   static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
>>   {
>>   	struct dw_pcie *pci = pcie->pci;
>> @@ -1439,8 +1466,10 @@ 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;
>> @@ -1511,6 +1540,22 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>>   	if (ret)
>>   		goto err_pm_runtime_put;
>>   
>> +	/* OPP table is optional */
>> +	ret = devm_pm_opp_of_add_table(dev);
>> +	if (ret && ret != -ENODEV) {
>> +		dev_err(dev, "Invalid OPP table in Device tree\n");
>> +		goto err_pm_runtime_put;
>> +	}
>> +
>> +	/* vote for max level in the opp table */
>> +	opp = dev_pm_opp_find_freq_floor(dev, &max_freq);
>> +	if (!IS_ERR(opp)) {
>> +		ret = dev_pm_opp_set_opp(dev, opp);
>> +		if (ret)
>> +			dev_err(pci->dev, "Failed to set opp: %d\n", ret);
>> +		dev_pm_opp_put(opp);
>> +	}
>> +
> This needs an update since you moved from frequency based voting to link
> speed based voting.

dev_pm_opp_find_freq_floor will give us the max the opp level opp we 
don't have a similar API to get max opp-level

For that reason we are using this API.

- KC

>
>>   	ret = pcie->cfg->ops->get_resources(pcie);
>>   	if (ret)
>>   		goto err_pm_runtime_put;
>> @@ -1531,6 +1576,8 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>>   
>>   	qcom_pcie_icc_update(pcie);
>>   
>> +	qcom_pcie_opp_update(pcie);
>> +
>>   	if (pcie->mhi)
>>   		qcom_pcie_init_debugfs(pcie);
>>   
>>
> Thanks,
> Pavan