linux-kernel - [PATCH v2 2/2] arm64: dts: exynos: Enable USB support on E850-96 board

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Message-Id: <20230825215445.28309-3-semen.protsenko@linaro.org>
Date:   Fri, 25 Aug 2023 16:54:45 -0500
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Conor Dooley <conor+dt@...nel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        JaeHun Jung <jh0801.jung@...sung.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] arm64: dts: exynos: Enable USB support on E850-96 board

The E850-96 board has a micro-USB socket and two USB 2.0 host sockets.
The USB role (host or peripheral) is selected automatically depending on
micro-USB cable attachment state:
  - micro-USB cable is attached: USB device role
  - micro-USB cable is detached: USB host role

USB can't act simultaneously as a device and a host, because Exynos850
SoC has only one USB controller and there are no external USB
controllers on the E850-96 board. So the USB switch chip (specifically
TS3USB221A) connects SoC USB lines either to micro-USB connector or to
USB hub chip (LAN9514), w.r.t. micro-USB cable attachment state.

When USB works in the host role, Ethernet capability becomes available
too, as the LAN9514 chip (providing USB hub) also enables Ethernet PHY
and Ethernet MAC.

Dynamic role switching is done in gpio-usb-b-connector, using current
micro-USB VBUS line level as a trigger:
  - VBUS=high: SoC USB lines are wired to micro-USB socket
  - VBUS=low: SoC USB lines are wired to USB hub chip

In order to make USB host functional when the board was booted with
micro-USB cable disconnected, role-switch-default-mode = "host" is used.

One can use E850-96 board schematics [1] to figure out how exactly all
related USB hardware connections and lines reflect into corresponding
device tree definitions.

As PMIC regulators are not implemented yet, we rely on USB LDOs being
already enabled in the bootloader. A dummy regulator is provided to
"usbdrd" vdd nodes for now.

[1] https://www.96boards.org/documentation/consumer/e850-96b/hardware-docs/

Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
---
Changes in v2:
  - none

 .../boot/dts/exynos/exynos850-e850-96.dts     | 58 +++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/arch/arm64/boot/dts/exynos/exynos850-e850-96.dts b/arch/arm64/boot/dts/exynos/exynos850-e850-96.dts
index 6ed38912507f..8d733361ef82 100644
--- a/arch/arm64/boot/dts/exynos/exynos850-e850-96.dts
+++ b/arch/arm64/boot/dts/exynos/exynos850-e850-96.dts
@@ -29,6 +29,22 @@ chosen {
 		stdout-path = &serial_0;
 	};
 
+	connector {
+		compatible = "gpio-usb-b-connector", "usb-b-connector";
+		label = "micro-USB";
+		type = "micro";
+		vbus-supply = <&reg_usb_host_vbus>;
+		id-gpios = <&gpa0 0 GPIO_ACTIVE_LOW>;
+		pinctrl-names = "default";
+		pinctrl-0 = <&micro_usb_det_pins>;
+
+		port {
+			usb_dr_connector: endpoint {
+				remote-endpoint = <&usb1_drd_sw>;
+			};
+		};
+	};
+
 	/*
 	 * RAM: 4 GiB (eMCP):
 	 *   - 2 GiB at 0x80000000
@@ -111,6 +127,20 @@ bt_active_led: led-5 {
 		};
 	};
 
+	/* TODO: Remove this once PMIC is implemented  */
+	reg_dummy: regulator-0 {
+		compatible = "regulator-fixed";
+		regulator-name = "dummy_reg";
+	};
+
+	reg_usb_host_vbus: regulator-1 {
+		compatible = "regulator-fixed";
+		regulator-name = "usb_host_vbus";
+		regulator-min-microvolt = <5000000>;
+		regulator-max-microvolt = <5000000>;
+		gpio = <&gpa3 5 GPIO_ACTIVE_LOW>;
+	};
+
 	/*
 	 * RTC clock (XrtcXTI); external, must be 32.768 kHz.
 	 *
@@ -172,6 +202,12 @@ key_volup_pins: key-volup-pins {
 		samsung,pin-pud = <EXYNOS_PIN_PULL_NONE>;
 		samsung,pin-drv = <EXYNOS5420_PIN_DRV_LV1>;
 	};
+
+	micro_usb_det_pins: micro-usb-det-pins {
+		samsung,pins = "gpa0-0";
+		samsung,pin-function = <EXYNOS_PIN_FUNC_INPUT>;
+		samsung,pin-pud = <EXYNOS_PIN_PULL_NONE>;
+	};
 };
 
 &rtc {
@@ -186,6 +222,28 @@ &serial_0 {
 	pinctrl-0 = <&uart1_pins>;
 };
 
+&usbdrd {
+	status = "okay";
+	vdd10-supply = <&reg_dummy>;
+	vdd33-supply = <&reg_dummy>;
+};
+
+&usbdrd_dwc3 {
+	dr_mode = "otg";
+	usb-role-switch;
+	role-switch-default-mode = "host";
+
+	port {
+		usb1_drd_sw: endpoint {
+			remote-endpoint = <&usb_dr_connector>;
+		};
+	};
+};
+
+&usbdrd_phy {
+	status = "okay";
+};
+
 &usi_uart {
 	samsung,clkreq-on; /* needed for UART mode */
 	status = "okay";
-- 
2.39.2