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

[Manivannan Sadhasivam]

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@xxxxxxxxxxxxxxxx>
> ---
>  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.

- Mani

-- 
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