linux-kernel - Re: [PATCH 3/3] PCI: qcom: Add D3cold support

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Message-ID: <7e61575a-3e0f-491d-ae22-89ab8bb21c91@oss.qualcomm.com>
Date: Fri, 30 Jan 2026 12:21:03 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Will Deacon <will@...nel.org>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        jonathanh@...dia.com
Subject: Re: [PATCH 3/3] PCI: qcom: Add D3cold support

On 1/29/26 6:27 AM, Krishna Chaitanya Chundru wrote:
> 
> 
> On 1/28/2026 5:58 PM, Konrad Dybcio wrote:
>> On 1/28/26 12:40 PM, Krishna Chaitanya Chundru wrote:
>>> Add pme_turn_off() support and use DWC common suspend resume methods
>>> for device D3cold entry & exit. If the device is not kept in D3cold
>>> use existing methods like keeping icc votes, opp votes etc.. intact.
>>>
>>> In qcom_pcie_deinit_2_7_0(), explicitly disable PCIe clocks and resets
>>> in the controller.
>>>
>>> Remove suspended flag from qcom_pcie structure as it is no longer needed.
>>>
>>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
>>> ---
>> [...]
>>
>>> +        /*
>>> +         * Only disable CPU-PCIe interconnect path if the suspend is non-S2RAM.
>>> +         * Because on some platforms, DBI access can happen very late during the
>>> +         * S2RAM and a non-active CPU-PCIe interconnect path may lead to NoC
>>> +         * error.
>>> +         */
>> I think someone internally once tracked down what that access was
> As per last debug which I have done few years back we see access coming IRQ driver to mask the interrupts
> as part of disabling non boot CPU's.
>> Can we fix that instead?
> The only proper fix is to keep device in D3cold which this patch is doing. if some client drivers like NVMe
> doesn't want to go D3cold we need to honor it, but Mani is working on it to allow NVMe drivers to go to D3cold.

That doesn't sound right - if there's an unclocked access, we should
either ensure that the PCIe controller is online for that write, or skip
the write if it's not possible for $reasons

Konrad