linux-kernel - Re: [PATCH] PCI: qcom: Use OPP only if the platform supports it

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Message-ID: <3c740b28-cb14-4d5d-ba0f-d8c658380ef7@quicinc.com>
Date: Mon, 22 Jul 2024 14:47:03 -0700
From: Mayank Rana <quic_mrana@...cinc.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        <lpieralisi@...nel.org>, <kw@...ux.com>
CC: <robh@...nel.org>, <bhelgaas@...gle.com>, <linux-arm-msm@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI: qcom: Use OPP only if the platform supports it

Hi Mani

On 7/22/2024 6:11 AM, Manivannan Sadhasivam wrote:
> With commit 5b6272e0efd5 ("PCI: qcom: Add OPP support to scale
> performance"), OPP was used to control the interconnect and power domains
> if the platform supported OPP. Also to maintain the backward compatibility
> with platforms not supporting OPP but just ICC, the above mentioned commit
> assumed that if ICC was not available on the platform, it would resort to
> OPP.
> 
> Unfortunately, some old platforms don't support either ICC or OPP. So on
> those platforms, resorting to OPP in the absence of ICC throws below errors
> from OPP core during suspend and resume:
> 
> qcom-pcie 1c08000.pcie: dev_pm_opp_set_opp: device opp doesn't exist
> qcom-pcie 1c08000.pcie: _find_key: OPP table not found (-19)
> 
> Also, it doesn't make sense to invoke the OPP APIs when OPP is not
> supported by the platform at all. So let's use a flag to identify whether
> OPP is supported by the platform or not and use it to control invoking the
> OPP APIs.
> 
> Fixes: 5b6272e0efd5 ("PCI: qcom: Add OPP support to scale performance")
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>   drivers/pci/controller/dwc/pcie-qcom.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 0180edf3310e..6f953e32d990 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -261,6 +261,7 @@ struct qcom_pcie {
>   	const struct qcom_pcie_cfg *cfg;
>   	struct dentry *debugfs;
>   	bool suspended;
> +	bool use_pm_opp;
>   };
>   
>   #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
> @@ -1433,7 +1434,7 @@ static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
>   			dev_err(pci->dev, "Failed to set bandwidth for PCIe-MEM interconnect path: %d\n",
>   				ret);
>   		}
> -	} else {
> +	} else if (pcie->use_pm_opp) {
>   		freq_mbps = pcie_dev_speed_mbps(pcie_link_speed[speed]);
>   		if (freq_mbps < 0)
>   			return;
> @@ -1592,6 +1593,8 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>   				      max_freq);
>   			goto err_pm_runtime_put;
>   		}
> +
> +		pcie->use_pm_opp = true;
>   	} else {
>   		/* Skip ICC init if OPP is supported as it is handled by OPP */
>   		ret = qcom_pcie_icc_init(pcie);
> @@ -1683,7 +1686,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>   		if (ret)
>   			dev_err(dev, "Failed to disable CPU-PCIe interconnect path: %d\n", ret);
>   
> -		if (!pcie->icc_mem)
> +		if (pcie->use_pm_opp)
>   			dev_pm_opp_set_opp(pcie->pci->dev, NULL);
>   	}
>   	return ret;
 >
Reviewed-by: Mayank Rana <quic_mrana@...cinc.com>

Regards,
Mayank