arm64: dts: ti: am642-phyboard-electra: Add overlay to enable PCIe

Add an overlay to enable PCIe on the am642-phyboard-electra. The
serdes is muxed from USB to PCIe, so we are restricted to USB2 while
using this overlay.
Signed-off-by: Nathan Morrisson <nmorrisson@phytec.com>
Reviewed-by: Wadim Egorov <w.egorov@phytec.de>
Link: https://lore.kernel.org/r/20240613195012.1925920-3-nmorrisson@phytec.comSigned-off-by: Vignesh Raghavendra <vigneshr@ti.com>

arch/arm64/boot/dts/ti/Makefile

@@ -51,6 +51,7 @@ dtb-$(CONFIG_ARCH_K3) += k3-am642-hummingboard-t-pcie.dtb
 dtb-$(CONFIG_ARCH_K3) += k3-am642-hummingboard-t-usb3.dtb
 dtb-$(CONFIG_ARCH_K3) += k3-am642-phyboard-electra-rdk.dtb
 dtb-$(CONFIG_ARCH_K3) += k3-am642-phyboard-electra-gpio-fan.dtbo
+dtb-$(CONFIG_ARCH_K3) += k3-am642-phyboard-electra-pcie-usb2.dtbo
 dtb-$(CONFIG_ARCH_K3) += k3-am642-sk.dtb
 dtb-$(CONFIG_ARCH_K3) += k3-am642-tqma64xxl-mbax4xxl.dtb
 dtb-$(CONFIG_ARCH_K3) += k3-am64-tqma64xxl-mbax4xxl-sdcard.dtbo
@@ -143,6 +144,8 @@ k3-am642-evm-icssg1-dualemac-mii-dtbs := \
 	k3-am642-evm.dtb k3-am642-evm-icssg1-dualemac-mii.dtbo
 k3-am642-phyboard-electra-gpio-fan-dtbs := \
 	k3-am642-phyboard-electra-rdk.dtb k3-am642-phyboard-electra-gpio-fan.dtbo
+k3-am642-phyboard-electra-pcie-usb2-dtbs := \
+	k3-am642-phyboard-electra-rdk.dtb k3-am642-phyboard-electra-pcie-usb2.dtbo
 k3-am642-tqma64xxl-mbax4xxl-sdcard-dtbs := \
 	k3-am642-tqma64xxl-mbax4xxl.dtb k3-am64-tqma64xxl-mbax4xxl-sdcard.dtbo
 k3-am642-tqma64xxl-mbax4xxl-wlan-dtbs := \

arch/arm64/boot/dts/ti/k3-am642-phyboard-electra-pcie-usb2.dtso

+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * DT overlay for PCIe support (limits USB to 2.0/high-speed)
+ *
+ * Copyright (C) 2021 PHYTEC America, LLC - https://www.phytec.com
+ * Author: Matt McKee <mmckee@phytec.com>
+ *
+ * Copyright (C) 2024 PHYTEC America, LLC - https://www.phytec.com
+ * Author: Nathan Morrisson <nmorrisson@phytec.com>
+ */
+
+/dts-v1/;
+/plugin/;
+
+#include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/phy/phy.h>
+#include <dt-bindings/phy/phy-cadence.h>
+
+#include "k3-pinctrl.h"
+#include "k3-serdes.h"
+
+&{/} {
+	pcie_refclk0: pcie-refclk0 {
+		compatible = "gpio-gate-clock";
+		pinctrl-names = "default";
+		pinctrl-0 = <&pcie_usb_sel_pins_default>;
+		clocks = <&serdes_refclk>;
+		#clock-cells = <0>;
+		enable-gpios = <&main_gpio1 7 GPIO_ACTIVE_HIGH>;
+	};
+};
+
+&main_pmx0 {
+	pcie_usb_sel_pins_default: pcie-usb-sel-default-pins {
+		pinctrl-single,pins = <
+			AM64X_IOPAD(0x017c, PIN_OUTPUT, 7)	/* (T1) PRG0_PRU0_GPO7.GPIO1_7 */
+		>;
+	};
+
+	pcie_pins_default: pcie-default-pins {
+		pinctrl-single,pins = <
+			AM64X_IOPAD(0x0098, PIN_OUTPUT, 7)	/* (W19) GPMC0_WAIT0.GPIO0_37 */
+		>;
+	};
+};
+
+&pcie0_rc {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pcie_pins_default>;
+	reset-gpios = <&main_gpio0 37 GPIO_ACTIVE_HIGH>;
+	phys = <&serdes0_pcie_usb_link>;
+	phy-names = "pcie-phy";
+	num-lanes = <1>;
+	status = "okay";
+};
+
+&serdes0_pcie_usb_link {
+	cdns,phy-type = <PHY_TYPE_PCIE>;
+};
+
+&serdes_ln_ctrl {
+	idle-states = <AM64_SERDES0_LANE0_PCIE0>;
+};
+
+&serdes0 {
+	assigned-clock-parents = <&pcie_refclk0>, <&pcie_refclk0>, <&pcie_refclk0>;
+};
+
+&serdes_refclk {
+	clock-frequency = <100000000>;
+};
+
+/*
+ * Assign pcie_refclk0 to serdes_wiz0 as ext_ref_clk.
+ * This makes sure that the clock generator gets enabled at the right time.
+ */
+&serdes_wiz0 {
+	clocks = <&k3_clks 162 0>, <&k3_clks 162 1>, <&pcie_refclk0>;
+};
+
+&usbss0 {
+	ti,usb2-only;
+};
+
+&usb0 {
+	maximum-speed = "high-speed";
+};