Re: [PATCH v11 6/6] PCI: qcom: Add OPP support to scale performance

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Tue, Apr 23, 2024 at 02:37:00PM +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.
> 
> 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>

Couple of nitpicks below. With that addressed,

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 81 ++++++++++++++++++++++++++++------
>  1 file changed, 67 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 465d63b4be1c..66bda30305a8 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>
> @@ -1443,15 +1444,13 @@ 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);
> @@ -1463,10 +1462,26 @@ 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 bandwidth for PCIe-MEM interconnect path: %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 bandwidth for PCIe-MEM interconnect path: %d\n",
> +				ret);
> +		}
> +	} else {
> +		mbps = pcie_link_speed_to_mbps(pcie_link_speed[speed]);

Don't use opaque variable names. Here it should be 'freq_mbps'.

> +		if (mbps < 0)
> +			return;
> +
> +		freq = mbps * 1000;

And this should be 'freq_kbps'.

> +		opp = dev_pm_opp_find_freq_exact(pci->dev, freq * width, true);
> +		if (!IS_ERR(opp)) {
> +			ret = dev_pm_opp_set_opp(pci->dev, opp);
> +			if (ret)
> +				dev_err(pci->dev, "Failed to set opp for freq (%ld): %d\n",

s/opp/OPP

> +					dev_pm_opp_get_freq(opp), ret);

Frequency is already available here, no? Hint: freq_kbps * width

> +		}
> +		dev_pm_opp_put(opp);
>  	}
>  }
>  
> @@ -1510,7 +1525,9 @@ 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 dev_pm_opp *opp;
>  	struct qcom_pcie *pcie;
>  	struct dw_pcie_rp *pp;
>  	struct resource *res;
> @@ -1578,9 +1595,42 @@ 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;
> +	}
> +
> +	/*
> +	 * 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. At the end of the probe(), OPP will be
> +	 * updated using qcom_pcie_icc_opp_update().
> +	 */
> +	if (!ret) {
> +		opp = dev_pm_opp_find_freq_floor(dev, &max_freq);
> +		if (IS_ERR(opp)) {
> +			dev_err_probe(pci->dev, PTR_ERR(opp),
> +				      "Unable to find max freq OPP\n");
> +			goto err_pm_runtime_put;
> +		} else {
> +			ret = dev_pm_opp_set_opp(dev, opp);
> +		}
> +
> +		dev_pm_opp_put(opp);
> +		if (ret) {
> +			dev_err_probe(pci->dev, ret,
> +				      "Failed to set OPP for freq (%ld): %d\n",

With dev_err_probe(), errno will be printed by default.

- Mani

-- 
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