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: <95078a8b-857d-4900-8737-a495212db935@quicinc.com>
Date:   Tue, 22 Aug 2023 09:33:48 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Krishna chaitanya chundru <quic_krichai@...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 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? 

> +	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().

> +
> +}
> +
>  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.

>  	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