Re: [PATCH v2 5/5] PCI: qcom: Add D3cold support

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

On 3/5/2026 2:44 PM, Manivannan Sadhasivam wrote:
> On Thu, Mar 05, 2026 at 02:30:17PM +0530, Krishna Chaitanya Chundru wrote:
>>
>> On 3/5/2026 1:28 PM, Manivannan Sadhasivam wrote:
>>> On Tue, Feb 17, 2026 at 04:49:10PM +0530, Krishna Chaitanya Chundru wrote:
>>>> Add support for transitioning Qcom PCIe controllers into D3cold by
>>> You cannot transition a 'PCIe controller' to D3Cold state, but only the
>>> endpoints and bridges.
>>>
>>>> integrating with the DWC core suspend/resume helpers.
>>>>
>>>> Implement PME_TurnOff message generation via ELBI_SYS_CTRL and hook it
>>>> into the DWC host operations so the controller follows the standard
>>>> PME_TurnOff-based power-down sequence before entering D3cold.
>>>>
>>>> When the link is suspended into D3cold, fully tear down interconnect
>>> You cannot suspend a link into D3Cold. Link and D-State are different.
>>>
>>>> bandwidth, OPP votes. If D3cold is not entered, retain existing behavior
>>>> by keeping the required interconnect and OPP votes.
>>>>
>>>> Drop the qcom_pcie::suspended flag and rely on the existing
>>>> dw_pcie::suspended state, which now drives both the power-management
>>>> flow and the interconnect/OPP handling.
>>>>
>>>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
>>>> ---
>>>>    drivers/pci/controller/dwc/pcie-qcom.c | 121 ++++++++++++++++++++-------------
>>>>    1 file changed, 74 insertions(+), 47 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>>>> index b02c19bbdf2ea5db252c2a0281a569bb3a0cc497..37442bbe588c36b0b0414cc4d0016da2d8424a87 100644
>>>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>>>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>>>> @@ -145,6 +145,7 @@
>>> [...]
>>>
>>>> -	if (pcie->suspended) {
>>>> -		ret = qcom_pcie_host_init(&pcie->pci->pp);
>>>> -		if (ret)
>>>> -			return ret;
>>>> +		ret = icc_enable(pcie->icc_mem);
>>>> +		if (ret) {
>>>> +			dev_err(dev, "Failed to enable PCIe-MEM interconnect path: %d\n", ret);
>>>> +			goto disable_icc_cpu;
>>>> +		}
>>>> -		pcie->suspended = false;
>>>> +		/*
>>>> +		 * Ignore -ETIMEDOUT here since it is expected when no endpoint is
>>>> +		 * connected to the PCIe link.
>>>> +		 */
>>>> +		ret = dw_pcie_resume_noirq(pcie->pci);
>>>> +		if (ret && (ret != -ETIMEDOUT))
>>> No, dw_pcie_resume_noirq() was reworked to return -ETIMEDOUT to indicate a hard
>>> failure. If the device is not found, it will return -ENODEV. So you should
>>> fail the resume if -ETIMEDOUT is returned.
>> Ack, didn't noticed the reworked changes, I will change -ETIMEDOUT to
>> -ENODEV.
>>
> No, that's what not I meant. I meant, you should do:
>
> 	if (ret == -ETIMEDOUT)
> 		goto fail;
there can be other failures also right, where we should fail,
like pci->pp.ops->init(&pci->pp); can return different error other than 
-ETIMEDOUT in that case we should fail here. - Krishna Chaitanya.
> - Mani
>