FROMLIST: PCI: qcom: Add D3cold support

Add support for transitioning PCIe endpoints under host bridge into
D3cold by 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 device is suspended into D3cold, fully tear down interconnect
bandwidth, OPP votes. If D3cold is not entered, retain existing behavior
by keeping the required interconnect and OPP votes.

Use dw_pcie::skip_pwrctrl_off to avoid powering off devices during suspend
to preserve wakeup capability of the devices and also not to power on the
devices in the init path.

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.

Link: https://lore.kernel.org/all/20260429-d3cold-v5-5-89e9735b9df6@oss.qualcomm.com/
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
Signed-off-by: Ziyue Zhang <ziyue.zhang@oss.qualcomm.com>

Author: krishnachaitanya-linux

drivers/pci/controller/dwc/pcie-qcom.c

@@ -1385,9 +1385,10 @@ static int qcom_pcie_host_init(struct dw_pcie_rp *pp)
 err_assert_reset:
 	qcom_pcie_perst_assert(pcie);
 err_pwrctrl_power_off:
-	pci_pwrctrl_power_off_devices(pci->dev);
+	if (!pp->skip_pwrctrl_off)
+		pci_pwrctrl_power_off_devices(pci->dev);
 err_pwrctrl_destroy:
-	if (ret != -EPROBE_DEFER)
+	if (ret != -EPROBE_DEFER && !pci->suspended)
 		pci_pwrctrl_destroy_devices(pci->dev);
 err_disable_phy:
 	qcom_pcie_phy_power_off(pcie);
@@ -2035,11 +2036,6 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
 	if (ret)
 		return ret;
 
-	if (pcie->pci->suspended)
-		dev_pm_genpd_rpm_always_on(dev, false);
-	else
-		dev_pm_genpd_rpm_always_on(dev, true);
-
 	if (pcie->pci->suspended) {
 		ret = icc_disable(pcie->icc_mem);
 		if (ret)