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

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Message-ID: <20250218220728.GA194681@bhelgaas>
Date: Tue, 18 Feb 2025 16:07:28 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
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

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?

> 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.

> +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.