linux-kernel - Re: [PATCH 4/8] PCI: dwc: qcom: Update ICC & OPP votes based upon the requested speed

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Message-ID: <f0e5efb7-8ea0-a064-21e4-6d7596b1a9ae@oss.qualcomm.com>
Date: Wed, 19 Feb 2025 23:28:47 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Johannes Berg <johannes@...solutions.net>,
        Jeff Johnson <jjohnson@...nel.org>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        mhi@...ts.linux.dev, linux-wireless@...r.kernel.org,
        ath11k@...ts.infradead.org, quic_jjohnson@...cinc.com,
        quic_pyarlaga@...cinc.com, quic_vbadigan@...cinc.com,
        quic_vpernami@...cinc.com, quic_mrana@...cinc.com
Subject: Re: [PATCH 4/8] PCI: dwc: qcom: Update ICC & OPP votes based upon the
 requested speed



On 2/19/2025 3:37 AM, Bjorn Helgaas wrote:
> Make subject line match history for this file.
> 
> On Mon, Feb 17, 2025 at 12:04:11PM +0530, Krishna Chaitanya Chundru wrote:
>> QCOM PCIe controllers needs to disable ASPM before initiating link
>> re-train. So as part of pre_bw_scale() disable ASPM and as part of
>> post_scale_bus_bw() enable ASPM back.
> 
> s/needs/need/
> 
> Why does Qcom need to disable ASPM?  Is there a PCIe spec restriction
> about this that should be applied to all PCIe host bridges?  Or is
> this a Qcom defect?
> 
It is QCOM controller issue, PCIe spec doesn't mention to disable ASPM.
>> Update ICC & OPP votes based on the requested speed so that RPMh votes
>> gets updated based on the speed.
> 
> s/gets/get/
> 
>> Bring out the core logic from qcom_pcie_icc_opp_update() to new function
>> qcom_pcie_set_icc_opp().
> 
> This refactoring possibly could be a separate patch to make the meat
> of this change clearer.
> 
ack.

- Krishna Chaitanya.
>> +static int qcom_pcie_set_icc_opp(struct qcom_pcie *pcie, int speed, int width)
>> +{
>> +	struct dw_pcie *pci = pcie->pci;
>> +	unsigned long freq_kbps;
>> +	struct dev_pm_opp *opp;
>> +	int ret, freq_mbps;
>> +
>> +	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 if (pcie->use_pm_opp) {
>> +		freq_mbps = pcie_dev_speed_mbps(pcie_link_speed[speed]);
>> +		if (freq_mbps < 0)
>> +			return -EINVAL;
>> +
>> +		freq_kbps = freq_mbps * KILO;
>> +		opp = dev_pm_opp_find_freq_exact(pci->dev, freq_kbps * 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 (%lu): %d\n",
>> +					freq_kbps * width, ret);
>> +			dev_pm_opp_put(opp);
>> +		}
>> +	}
>> +
>> +	return ret;
> 
> Looks uninitialized in some paths.