[PATCH v2 2/2] ARM: dts: am335x-bone-common: Add GPIO PHY reset on revision C3 board

[Shengyu Qu]

This patch adds ethernet PHY reset GPIO config for Beaglebone Black
series boards with revision C3. This fixes a random phy startup failure
bug discussed at [1]. The GPIO pin used for reset is not used on older
revisions, so it is ok to apply to all board revisions. The reset timing
was discussed and tested at [2].

[1] https://forum.digikey.com/t/ethernet-device-is-not-detecting-on-ubuntu-20-04-lts-on-bbg/19948
[2] https://forum.beagleboard.org/t/recognizing-a-beaglebone-black-rev-c3-board/31249/

Signed-off-by: Robert Nelson <robertcnelson@xxxxxxxxx>
Signed-off-by: Shengyu Qu <wiagn233@xxxxxxxxxxx>
---
Changes since v1:
 - Using /**/ rather than // to comment
---
 arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi b/arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi
index 7b784a87efc6..96451c8a815c 100644
--- a/arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi
+++ b/arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi
@@ -145,6 +145,8 @@ davinci_mdio_default: davinci-mdio-default-pins {
 			/* MDIO */
 			AM33XX_PADCONF(AM335X_PIN_MDIO, PIN_INPUT_PULLUP | SLEWCTRL_FAST, MUX_MODE0)
 			AM33XX_PADCONF(AM335X_PIN_MDC, PIN_OUTPUT_PULLUP, MUX_MODE0)
+			/* Added to support GPIO controlled PHY reset */
+			AM33XX_PADCONF(AM335X_PIN_UART0_CTSN, PIN_OUTPUT_PULLUP, MUX_MODE7)
 		>;
 	};
 
@@ -153,6 +155,8 @@ davinci_mdio_sleep: davinci-mdio-sleep-pins {
 			/* MDIO reset value */
 			AM33XX_PADCONF(AM335X_PIN_MDIO, PIN_INPUT_PULLDOWN, MUX_MODE7)
 			AM33XX_PADCONF(AM335X_PIN_MDC, PIN_INPUT_PULLDOWN, MUX_MODE7)
+			/* Added to support GPIO controlled PHY reset */
+			AM33XX_PADCONF(AM335X_PIN_UART0_CTSN, PIN_INPUT_PULLDOWN, MUX_MODE7)
 		>;
 	};
 
@@ -378,6 +382,10 @@ &davinci_mdio_sw {
 
 	ethphy0: ethernet-phy@0 {
 		reg = <0>;
+		/* Support GPIO reset on revision C3 boards */
+		reset-gpios = <&gpio1 8 GPIO_ACTIVE_LOW>;
+		reset-assert-us = <300>;
+		reset-deassert-us = <6500>;
 	};
 };
 
-- 
2.41.0