linux-kernel - Re: [PATCH v2 3/3] PCI: qcom: properly implement RC shutdown/power up

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Message-ID: <653f43a4-c05a-4086-b87f-abed88dbb28b@linaro.org>
Date: Wed, 27 Mar 2024 20:37:04 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczyński <kw@...ux.com>,
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Philipp Zabel <p.zabel@...gutronix.de>
Cc: linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, Johan Hovold <johan+linaro@...nel.org>,
 Bjorn Andersson <quic_bjorande@...cinc.com>
Subject: Re: [PATCH v2 3/3] PCI: qcom: properly implement RC shutdown/power up

On 20.02.2024 5:12 AM, Krishna Chaitanya Chundru wrote:
> 
> 
> On 2/10/2024 10:40 PM, Konrad Dybcio wrote:
>> Currently, we've only been minimizing the power draw while keeping the
>> RC up at all times. This is suboptimal, as it draws a whole lot of power
>> and prevents the SoC from power collapsing.
>>
>> Implement full shutdown and re-initialization to allow for powering off
>> the controller.
>>
>> This is mainly indended for SC8280XP with a broken power rail setup,
>> which requires a full RC shutdown/reinit in order to reach SoC-wide
>> power collapse, but sleeping is generally better than not sleeping and
>> less destructive suspend can be implemented later for platforms that
>> support it.
>>
>> Co-developed-by: Bjorn Andersson <quic_bjorande@...cinc.com>
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>> ---

[...]


>> +    if (pcie->soc_is_rpmh) {
>> +        /*
>> +         * The PCIe RC may be covertly accessed by the secure firmware
>> +         * on sleep exit. Use the WAKE bucket to let RPMh pull the plug
>> +         * on PCIe in sleep, but guarantee it comes back up for resume.
>> +         */
>> +        icc_set_tag(pcie->icc_mem, QCOM_ICC_TAG_WAKE);
>> +
>> +        /* Flush the tag change */
>> +        ret = icc_enable(pcie->icc_mem);
>> +        if (ret) {
>> +            dev_err(pcie->pci->dev, "failed to icc_enable %d\n", ret);
>> +
>> +            /* Revert everything and pray icc calls succeed */
>> +            return qcom_pcie_resume_noirq(dev);
>> +        }
>> +    } else {
>> +        /*
>> +         * Set minimum bandwidth required to keep data path functional
>> +         * during suspend.
>> +         */
> calling qcom_pcie_host_deinit(&pcie->pci->pp) above will turn off all the resources, setting BW to 1Kbps will not make sense here.

This is preserving the current behavior, it may be revised later.

See ad9b9b6e36c9 ("PCI: qcom: Add support for system suspend and resume")
that introduced it, in a perhaps overly 8280-centric fashion.

Konrad