samsung: board: support eMMC reset using DT

Some exynos boards require special handling of nRESET_OUT line for eMMC
memory to perform complete reboot e.g. Odroid X2/U3/XU3 boards.

This will support eMMC reset using DT from reset_misc of samsung common
board file.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>

board/samsung/common/board.c

@@ -355,3 +355,31 @@ int misc_init_r(void)
 	return 0;
 }
 #endif
+
+void reset_misc(void)
+{
+	struct gpio_desc gpio = {};
+	int node;
+
+	node = fdt_node_offset_by_compatible(gd->fdt_blob, 0,
+			"samsung,emmc-reset");
+	if (node < 0)
+		return;
+
+	gpio_request_by_name_nodev(gd->fdt_blob, node, "reset-gpio", 0, &gpio,
+				   GPIOD_IS_OUT);
+
+	if (dm_gpio_is_valid(&gpio)) {
+		/*
+		 * Reset eMMC
+		 *
+		 * FIXME: Need to optimize delay time. Minimum 1usec pulse is
+		 *	  required by 'JEDEC Standard No.84-A441' (eMMC)
+		 *	  document but real delay time is expected to greater
+		 *	  than 1usec.
+		 */
+		dm_gpio_set_value(&gpio, 0);
+		mdelay(10);
+		dm_gpio_set_value(&gpio, 1);
+	}
+}

board/samsung/odroid/odroid.c

@@ -503,11 +503,3 @@ int board_usb_init(int index, enum usb_init_type init)
 	return s3c_udc_probe(&s5pc210_otg_data);
 }
 #endif
-
-void reset_misc(void)
-{
-	/* Reset eMMC*/
-	gpio_set_value(EXYNOS4X12_GPIO_K12, 0);
-	mdelay(10);
-	gpio_set_value(EXYNOS4X12_GPIO_K12, 1);
-}

doc/device-tree-bindings/exynos/emmc-reset.txt

@@ -0,0 +1,15 @@
+* Samsung eMMC reset
+
+Some exynos boards require special handling of nRESET_OUT line for eMMC memory
+to perform complete reboot.
+
+Required properties:
+- compatible: should be "samsung,emmc-reset"
+- reset-gpio: gpio chip for eMMC reset.
+
+Example:
+
+emmc-reset {
+        compatible = "samsung,emmc-reset";
+        reset-gpio = <&gpk1 2 0>;
+};