PCI: imx6: Factor out ref clock enable

Factor out ref clock enable to make it cleaner to add imx6sx support.  No
functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Christoph Fritz <chf.fritz@googlemail.com>

drivers/pci/host/pci-imx6.c

@@ -269,6 +269,23 @@ static int imx6_pcie_assert_core_reset(struct pcie_port *pp)
 	return 0;
 }
 
+static int imx6_pcie_enable_ref_clk(struct imx6_pcie *imx6_pcie)
+{
+	/* power up core phy and enable ref clock */
+	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
+			IMX6Q_GPR1_PCIE_TEST_PD, 0 << 18);
+	/*
+	 * the async reset input need ref clock to sync internally,
+	 * when the ref clock comes after reset, internal synced
+	 * reset time is too short, cannot meet the requirement.
+	 * add one ~10us delay here.
+	 */
+	udelay(10);
+	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
+			IMX6Q_GPR1_PCIE_REF_CLK_EN, 1 << 16);
+	return 0;
+}
+
 static int imx6_pcie_deassert_core_reset(struct pcie_port *pp)
 {
 	struct imx6_pcie *imx6_pcie = to_imx6_pcie(pp);
@@ -292,18 +309,11 @@ static int imx6_pcie_deassert_core_reset(struct pcie_port *pp)
 		goto err_pcie;
 	}
 
-	/* power up core phy and enable ref clock */
-	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
-			IMX6Q_GPR1_PCIE_TEST_PD, 0 << 18);
-	/*
-	 * the async reset input need ref clock to sync internally,
-	 * when the ref clock comes after reset, internal synced
-	 * reset time is too short, cannot meet the requirement.
-	 * add one ~10us delay here.
-	 */
-	udelay(10);
-	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
-			IMX6Q_GPR1_PCIE_REF_CLK_EN, 1 << 16);
+	ret = imx6_pcie_enable_ref_clk(imx6_pcie);
+	if (ret) {
+		dev_err(pp->dev, "unable to enable pcie ref clock\n");
+		goto err_ref_clk;
+	}
 
 	/* allow the clocks to stabilize */
 	usleep_range(200, 500);
@@ -316,6 +326,8 @@ static int imx6_pcie_deassert_core_reset(struct pcie_port *pp)
 	}
 	return 0;
 
+err_ref_clk:
+	clk_disable_unprepare(imx6_pcie->pcie);
 err_pcie:
 	clk_disable_unprepare(imx6_pcie->pcie_bus);
 err_pcie_bus: