pitx-imx8m: fix UART3 and USB1_OTG iomux settings for rev2

Due to HW design errors in rev2, some signals must be reconfigured
to avoid malfunction or possible electrical damage.
- Setup UART3 RTS/CTS lines as GPIOs as polarity has been swapped on rev2
- Make sure to set GPIO1_IO12 (USB1_OTG_PWR) in input mode and remove usb0
  port from u-boot device tree to avoid conflicting drivers when external
  host is attached.
Signed-off-by: Thomas Schaefer <thomas.schaefer@kontron.com>

board/kontron/pitx-imx8m/pitx-imx8m.c

@@ -35,6 +35,7 @@
 #include <dwc3-uboot.h>
 #include <i2c.h>
 #include <search.h>
+#include <mapmem.h>
 
 #include "pitx-imx8m.h"
 #include "../common/emb_eep.h"
@@ -530,15 +531,46 @@ int misc_init_r(void)
 	hw_rev = get_hw_rev();
 	/* check if hw variant is L120 (7) */
 	if (hw_rev == 7) {
+		int nodeoffset;
+		void *fdt = map_sysmem((ulong)gd->fdt_blob, 0);
+
 		imx_iomux_v3_setup_pad(IMX8MQ_PAD_ECSPI1_MISO__GPIO5_IO8 |
-		                       MUX_PAD_CTRL(UART_PAD_CTRL));
+				       MUX_PAD_CTRL(UART_PAD_CTRL));
 		imx_iomux_v3_setup_pad(IMX8MQ_PAD_ECSPI1_SS0__GPIO5_IO9 |
-		                       MUX_PAD_CTRL(UART_PAD_CTRL | PAD_CTL_PUE));
+				       MUX_PAD_CTRL(UART_PAD_CTRL | PAD_CTL_PUE));
 
 		gpio_request(IMX_GPIO_NR(5, 8), "UART3_CTS#");
 		gpio_direction_output(IMX_GPIO_NR(5, 8), 0);
 		gpio_request(IMX_GPIO_NR(5, 9), "UART3_RTS#");
 		gpio_direction_input(IMX_GPIO_NR(5, 9));
+
+		/*
+		 * Set SION for GPIO1_IO12 pad. This ensures that the pad
+		 * cannot be put into GPIO output mode by the CLI 'gpio'
+		 * command causing TPS2062 OUT2 to drive against
+		 * V_5V0_USB1_OTG_VBUS voltage line from external host.
+		 *
+		 * In addition, usb0 port is removed from the u-boot device
+		 * tree. This ensures that SION setting is not overwritten
+		 * when 'usb start' is invoked.
+		 */
+		imx_iomux_v3_setup_pad(IMX8MQ_PAD_GPIO1_IO12__GPIO1_IO12 |
+				       MUX_PAD_CTRL(NO_PAD_CTRL) |
+				       MUX_MODE_SION);
+
+		/*
+		 * Remove USB OTG port (usb0) from the device tree as we cannot
+		 * use it in host mode on rev2 modules. However, using the ums
+		 * command is still possible.
+		 */
+		nodeoffset = fdt_path_offset (fdt, "usb0");
+		if (nodeoffset < 0) {
+			printf("libfdt path 'usb0' not found,"
+			        " cannot remove usb0 node\n");
+			return 0; /* No need to return an error code here */
+		}
+		if (!fdt_del_node (fdt, nodeoffset))
+			printf("Rev2 module: removing USB OTG port from DT\n");
 	}
 
 	return 0;