PCI: layerscape: Add function pointer for exit_from_l2()

Since different SoCs require different sequences for exiting L2, let's add
a separate "exit_from_l2()" callback to handle SoC specific sequences.

Change ls_pcie_exit_from_l2() return value from void to int in order
to propagate errors. Return an error if the exit_from_l2() callback
fails in the resume flow.

Link: https://lore.kernel.org/r/20231204160829.2498703-2-Frank.Li@nxp.com
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Roy Zang <Roy.Zang@nxp.com>

Author: nxpfrankli

drivers/pci/controller/dwc/pci-layerscape.c

@@ -39,6 +39,7 @@
 
 struct ls_pcie_drvdata {
 	const u32 pf_off;
+	int (*exit_from_l2)(struct dw_pcie_rp *pp);
 	bool pm_support;
 };
 
@@ -125,7 +126,7 @@ static void ls_pcie_send_turnoff_msg(struct dw_pcie_rp *pp)
 		dev_err(pcie->pci->dev, "PME_Turn_off timeout\n");
 }
 
-static void ls_pcie_exit_from_l2(struct dw_pcie_rp *pp)
+static int ls_pcie_exit_from_l2(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct ls_pcie *pcie = to_ls_pcie(pci);
@@ -150,6 +151,8 @@ static void ls_pcie_exit_from_l2(struct dw_pcie_rp *pp)
 				 10000);
 	if (ret)
 		dev_err(pcie->pci->dev, "L2 exit timeout\n");
+
+	return ret;
 }
 
 static int ls_pcie_host_init(struct dw_pcie_rp *pp)
@@ -180,6 +183,7 @@ static const struct ls_pcie_drvdata ls1021a_drvdata = {
 static const struct ls_pcie_drvdata layerscape_drvdata = {
 	.pf_off = 0xc0000,
 	.pm_support = true,
+	.exit_from_l2 = ls_pcie_exit_from_l2,
 };
 
 static const struct of_device_id ls_pcie_of_match[] = {
@@ -247,11 +251,14 @@ static int ls_pcie_suspend_noirq(struct device *dev)
 static int ls_pcie_resume_noirq(struct device *dev)
 {
 	struct ls_pcie *pcie = dev_get_drvdata(dev);
+	int ret;
 
 	if (!pcie->drvdata->pm_support)
 		return 0;
 
-	ls_pcie_exit_from_l2(&pcie->pci->pp);
+	ret = pcie->drvdata->exit_from_l2(&pcie->pci->pp);
+	if (ret)
+		return ret;
 
 	return dw_pcie_resume_noirq(pcie->pci);
 }