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Date: Wed, 27 Mar 2024 20:37:04 +0100
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Subject: Re: [PATCH v2 3/3] PCI: qcom: properly implement RC shutdown/power up
To: Krishna Chaitanya Chundru <quic_krichai@quicinc.com>,
 Bjorn Andersson <andersson@kernel.org>,
 Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
 Lorenzo Pieralisi <lpieralisi@kernel.org>,
 =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= <kw@linux.com>,
 Rob Herring <robh@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
 Philipp Zabel <p.zabel@pengutronix.de>
Cc: linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org,
 linux-kernel@vger.kernel.org, Johan Hovold <johan+linaro@kernel.org>,
 Bjorn Andersson <quic_bjorande@quicinc.com>
References: <20240210-topic-8280_pcie-v2-0-1cef4b606883@linaro.org>
 <20240210-topic-8280_pcie-v2-3-1cef4b606883@linaro.org>
 <39f28d21-e178-68df-c7b6-eef30f0584e3@quicinc.com>
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From: Konrad Dybcio <konrad.dybcio@linaro.org>
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In-Reply-To: <39f28d21-e178-68df-c7b6-eef30f0584e3@quicinc.com>
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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@quicinc.com>
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.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