PCI: imx6: Add DT bindings to configure PHY Tx driver settings

The settings in GPR8 are dependent upon the particular layout of the
hardware platform.  As such, they should be configurable via the device
tree.

Look up PHY Tx driver settings from the device tree.  Fall back to the
original hard-coded values if they are not specified in the device tree.

Signed-off-by: Justin Waters <justin.waters@timesys.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Lucas Stach <l.stach@pengutronix.de>

Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt

@@ -13,6 +13,13 @@ Required properties:
 - clock-names: Must include the following additional entries:
 	- "pcie_phy"
 
+Optional properties:
+- fsl,tx-deemph-gen1: Gen1 De-emphasis value. Default: 0
+- fsl,tx-deemph-gen2-3p5db: Gen2 (3.5db) De-emphasis value. Default: 0
+- fsl,tx-deemph-gen2-6db: Gen2 (6db) De-emphasis value. Default: 20
+- fsl,tx-swing-full: Gen2 TX SWING FULL value. Default: 127
+- fsl,tx-swing-low: TX launch amplitude swing_low value. Default: 127
+
 Example:
 
 	pcie@0x01000000 {

drivers/pci/host/pci-imx6.c

@@ -39,6 +39,11 @@ struct imx6_pcie {
 	struct pcie_port	pp;
 	struct regmap		*iomuxc_gpr;
 	void __iomem		*mem_base;
+	u32			tx_deemph_gen1;
+	u32			tx_deemph_gen2_3p5db;
+	u32			tx_deemph_gen2_6db;
+	u32			tx_swing_full;
+	u32			tx_swing_low;
 };
 
 /* PCIe Root Complex registers (memory-mapped) */
@@ -334,15 +339,20 @@ static void imx6_pcie_init_phy(struct pcie_port *pp)
 			IMX6Q_GPR12_LOS_LEVEL, 9 << 4);
 
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR8,
-			IMX6Q_GPR8_TX_DEEMPH_GEN1, 0 << 0);
+			   IMX6Q_GPR8_TX_DEEMPH_GEN1,
+			   imx6_pcie->tx_deemph_gen1 << 0);
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR8,
-			IMX6Q_GPR8_TX_DEEMPH_GEN2_3P5DB, 0 << 6);
+			   IMX6Q_GPR8_TX_DEEMPH_GEN2_3P5DB,
+			   imx6_pcie->tx_deemph_gen2_3p5db << 6);
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR8,
-			IMX6Q_GPR8_TX_DEEMPH_GEN2_6DB, 20 << 12);
+			   IMX6Q_GPR8_TX_DEEMPH_GEN2_6DB,
+			   imx6_pcie->tx_deemph_gen2_6db << 12);
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR8,
-			IMX6Q_GPR8_TX_SWING_FULL, 127 << 18);
+			   IMX6Q_GPR8_TX_SWING_FULL,
+			   imx6_pcie->tx_swing_full << 18);
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR8,
-			IMX6Q_GPR8_TX_SWING_LOW, 127 << 25);
+			   IMX6Q_GPR8_TX_SWING_LOW,
+			   imx6_pcie->tx_swing_low << 25);
 }
 
 static int imx6_pcie_wait_for_link(struct pcie_port *pp)
@@ -533,6 +543,7 @@ static int __init imx6_pcie_probe(struct platform_device *pdev)
 	struct imx6_pcie *imx6_pcie;
 	struct pcie_port *pp;
 	struct resource *dbi_base;
+	struct device_node *node = pdev->dev.of_node;
 	int ret;
 
 	imx6_pcie = devm_kzalloc(&pdev->dev, sizeof(*imx6_pcie), GFP_KERNEL);
@@ -585,6 +596,27 @@ static int __init imx6_pcie_probe(struct platform_device *pdev)
 		return PTR_ERR(imx6_pcie->iomuxc_gpr);
 	}
 
+	/* Grab PCIe PHY Tx Settings */
+	if (of_property_read_u32(node, "fsl,tx-deemph-gen1",
+				 &imx6_pcie->tx_deemph_gen1))
+		imx6_pcie->tx_deemph_gen1 = 0;
+
+	if (of_property_read_u32(node, "fsl,tx-deemph-gen2-3p5db",
+				 &imx6_pcie->tx_deemph_gen2_3p5db))
+		imx6_pcie->tx_deemph_gen2_3p5db = 0;
+
+	if (of_property_read_u32(node, "fsl,tx-deemph-gen2-6db",
+				 &imx6_pcie->tx_deemph_gen2_6db))
+		imx6_pcie->tx_deemph_gen2_6db = 20;
+
+	if (of_property_read_u32(node, "fsl,tx-swing-full",
+				 &imx6_pcie->tx_swing_full))
+		imx6_pcie->tx_swing_full = 127;
+
+	if (of_property_read_u32(node, "fsl,tx-swing-low",
+				 &imx6_pcie->tx_swing_low))
+		imx6_pcie->tx_swing_low = 127;
+
 	ret = imx6_add_pcie_port(pp, pdev);
 	if (ret < 0)
 		return ret;