Re: [PATCH v4 4/4] PCI: qcom: Add OPP support for speed based performance state of RPMH

[Krishna Chaitanya Chundru <quic_krichai@quicinc.com>]

On 8/23/2023 12:36 PM, Manivannan Sadhasivam wrote:
> Subject should be, "PCI: qcom: Add OPP support to scale performance state of
> power domain"
>
> On Tue, Aug 22, 2023 at 08:42:21PM +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.
>>
> Commit message should have the justification on why OPP support should be
> addded, not just how you add it. The reasoning should be, "While scaling the
> interconnect clocks based on PCIe link speed, it is also mandatory to scale the
> power domain performance state so that the SoC can run under optimum power
> conditions."
done
>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 52 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 52 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index 7a87a47..161fdad 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 +1358,33 @@ 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;
>> +
>> +	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
>> +
> Since icc_update() also queries link status register, this could be moved inside
> icc_update() to avoid code duplication and probably the function con be renamed
> to "qcom_pcie_icc_opp_update()".
done
>> +	opp = dev_pm_opp_find_level_exact(pci->dev, speed);
>> +	if (!IS_ERR(opp)) {
> As we decided for pcie-qcom-ep, let's return error from _update() function if
> icc paths/opp support were specified in DT.
>
> Use a separate patch for returning error from existing qcom_pcie_icc_update()
> function and add opp support on top.
done
>> +		ret = dev_pm_opp_set_opp(pci->dev, opp);
>> +		if (ret)
>> +			dev_err(pci->dev, "Failed to set opp: level %d ret %d\n",
>> +						dev_pm_opp_get_level(opp), ret);
>> +		dev_pm_opp_put(opp);
>> +	}
>> +
>> +}
>> +
>>   static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
>>   {
>>   	struct dw_pcie *pci = pcie->pci;
>> @@ -1439,8 +1467,10 @@ 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_level = 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 +1541,23 @@ 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");
> "Failed to add OPP table"
>
> Also, use dev_err_probe() here and below.
>
>> +		goto err_pm_runtime_put;
>> +	}
>> +
>> +	/* vote for max level in the opp table */
>> +	opp = dev_pm_opp_find_level_floor(dev, &max_level);
> Use a bool flag to check whether opp support is present or not and use that to
> decide calling these APIs.
done
>> +	if (!IS_ERR(opp)) {
>> +		ret = dev_pm_opp_set_opp(dev, opp);
>> +		if (ret)
>> +			dev_err(pci->dev, "Failed to set opp: level %d ret %d\n",
>> +						dev_pm_opp_get_level(opp), ret);
>> +		dev_pm_opp_put(opp);
>> +	}
>> +
>>   	ret = pcie->cfg->ops->get_resources(pcie);
>>   	if (ret)
>>   		goto err_pm_runtime_put;
>> @@ -1531,6 +1578,8 @@ 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);
>>   
>> @@ -1577,6 +1626,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>>   	 */
>>   	if (!dw_pcie_link_up(pcie->pci)) {
>>   		qcom_pcie_host_deinit(&pcie->pci->pp);
>> +		dev_pm_opp_set_opp(dev, NULL);
> This will print error when OPP table was not specified in DT. So use the flag as
> I suggested above.
>
> - Mani

done

- KC

>>   		pcie->suspended = true;
>>   	}
>>   
>> @@ -1593,6 +1643,8 @@ static int qcom_pcie_resume_noirq(struct device *dev)
>>   		if (ret)
>>   			return ret;
>>   
>> +		qcom_pcie_opp_update(pcie);
>> +
>>   		pcie->suspended = false;
>>   	}
>>   
>> -- 
>> 2.7.4
>>