linux-kernel - Re: [PATCH v6 3/6] PCI: qcom: Add missing icc bandwidth vote for cpu to PCIe path

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Message-ID: <ZaFhzOCTpZYlAh60@hovoldconsulting.com>
Date: Fri, 12 Jan 2024 16:59:08 +0100
From: Johan Hovold <johan@...nel.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Johan Hovold <johan+linaro@...nel.org>,
	Brian Masney <bmasney@...hat.com>,
	Georgi Djakov <djakov@...nel.org>, linux-arm-msm@...r.kernel.org,
	vireshk@...nel.org, quic_vbadigan@...cinc.com,
	quic_skananth@...cinc.com, quic_nitegupt@...cinc.com,
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v6 3/6] PCI: qcom: Add missing icc bandwidth vote for cpu
 to PCIe path

On Fri, Jan 12, 2024 at 07:52:02PM +0530, Krishna chaitanya chundru wrote:
> CPU-PCIe path consits for registers PCIe BAR space, config space.

consits?

> As there is less access on this path compared to pcie to mem path
> add minimum vote i.e GEN1x1 bandwidth always.

gen1 bandwidth can't be right.

> In suspend remove the cpu vote after register space access is done.
> 
> Fixes: c4860af88d0c ("PCI: qcom: Add basic interconnect support")
> cc: stable@...r.kernel.org

This does not look like a fix so drop the above.

The commit you refer to explicitly left this path unconfigured for now
and only added support for the configuring the mem path as needed on
sc8280xp which otherwise would crash.

> @@ -1573,7 +1588,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  	 */
>  	ret = icc_set_bw(pcie->icc_mem, 0, kBps_to_icc(1));
>  	if (ret) {
> -		dev_err(dev, "Failed to set interconnect bandwidth: %d\n", ret);
> +		dev_err(dev, "Failed to set interconnect bandwidth for pcie-mem: %d\n", ret);
>  		return ret;
>  	}
>  
> @@ -1597,6 +1612,12 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  		pcie->suspended = true;
>  	}
>  
> +	/* Remove cpu path vote after all the register access is done */
> +	ret = icc_set_bw(pcie->icc_cpu, 0, 0);

I believe you should use icc_disable() here.

> +	if (ret) {
> +		dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
> +		return ret;

And you need to unwind before returning on errors.

> +	}
>  	return 0;
>  }
>  
> @@ -1605,6 +1626,12 @@ static int qcom_pcie_resume_noirq(struct device *dev)
>  	struct qcom_pcie *pcie = dev_get_drvdata(dev);
>  	int ret;
>  
> +	ret = icc_set_bw(pcie->icc_cpu, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));

icc_enable()

> +	if (ret) {
> +		dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
> +		return ret;
> +	}

Johan