PCI: mediatek: Add system PM support for MT2712 and MT7622

In order to reduce the PCIe power consumption in system suspend,
the PCI bus physical layer should be gated. On system resume, the PCIe
link should be re-established and the related control register values
should be restored.

Define suspend_noirq & resume_noirq callback functions to implement
PM system syspend hooks for the PCI host controller.

Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
[lorenzo.pieralisi@arm.com: updated commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Ryder Lee <ryder.lee@mediatek.com>

drivers/pci/controller/pcie-mediatek.c

@@ -1168,6 +1168,55 @@ put_resources:
 	return err;
 }
 
+static int __maybe_unused mtk_pcie_suspend_noirq(struct device *dev)
+{
+	struct mtk_pcie *pcie = dev_get_drvdata(dev);
+	struct mtk_pcie_port *port;
+
+	if (list_empty(&pcie->ports))
+		return 0;
+
+	list_for_each_entry(port, &pcie->ports, list) {
+		clk_disable_unprepare(port->pipe_ck);
+		clk_disable_unprepare(port->obff_ck);
+		clk_disable_unprepare(port->axi_ck);
+		clk_disable_unprepare(port->aux_ck);
+		clk_disable_unprepare(port->ahb_ck);
+		clk_disable_unprepare(port->sys_ck);
+		phy_power_off(port->phy);
+		phy_exit(port->phy);
+	}
+
+	clk_disable_unprepare(pcie->free_ck);
+
+	return 0;
+}
+
+static int __maybe_unused mtk_pcie_resume_noirq(struct device *dev)
+{
+	struct mtk_pcie *pcie = dev_get_drvdata(dev);
+	struct mtk_pcie_port *port, *tmp;
+
+	if (list_empty(&pcie->ports))
+		return 0;
+
+	clk_prepare_enable(pcie->free_ck);
+
+	list_for_each_entry_safe(port, tmp, &pcie->ports, list)
+		mtk_pcie_enable_port(port);
+
+	/* In case of EP was removed while system suspend. */
+	if (list_empty(&pcie->ports))
+		clk_disable_unprepare(pcie->free_ck);
+
+	return 0;
+}
+
+static const struct dev_pm_ops mtk_pcie_pm_ops = {
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(mtk_pcie_suspend_noirq,
+				      mtk_pcie_resume_noirq)
+};
+
 static const struct mtk_pcie_soc mtk_pcie_soc_v1 = {
 	.ops = &mtk_pcie_ops,
 	.startup = mtk_pcie_startup_port,
@@ -1200,6 +1249,7 @@ static struct platform_driver mtk_pcie_driver = {
 		.name = "mtk-pcie",
 		.of_match_table = mtk_pcie_ids,
 		.suppress_bind_attrs = true,
+		.pm = &mtk_pcie_pm_ops,
 	},
 };
 builtin_platform_driver(mtk_pcie_driver);