i.MX6Q: mx6qsabrelite: Add keypress support to alter boot flow

Uses the 'magic_keys' idiom as described in doc/README.kbd:
	http://lists.denx.de/pipermail/u-boot/2012-April/122502.html

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>

board/freescale/mx6qsabrelite/mx6qsabrelite.c

@@ -50,6 +50,10 @@ DECLARE_GLOBAL_DATA_PTR;
 	PAD_CTL_PUS_100K_DOWN | PAD_CTL_SPEED_MED |		\
 	PAD_CTL_DSE_40ohm     | PAD_CTL_SRE_FAST)
 
+#define BUTTON_PAD_CTRL (PAD_CTL_PKE | PAD_CTL_PUE |		\
+	PAD_CTL_PUS_100K_UP | PAD_CTL_SPEED_MED   |		\
+	PAD_CTL_DSE_40ohm   | PAD_CTL_HYS)
+
 int dram_init(void)
 {
        gd->ram_size = get_ram_size((void *)PHYS_SDRAM, PHYS_SDRAM_SIZE);
@@ -122,6 +126,22 @@ iomux_v3_cfg_t enet_pads2[] = {
 	MX6Q_PAD_RGMII_RX_CTL__RGMII_RX_CTL	| MUX_PAD_CTRL(ENET_PAD_CTRL),
 };
 
+/* Button assignments for J14 */
+static iomux_v3_cfg_t button_pads[] = {
+	/* Menu */
+	MX6Q_PAD_NANDF_D1__GPIO_2_1	| MUX_PAD_CTRL(BUTTON_PAD_CTRL),
+	/* Back */
+	MX6Q_PAD_NANDF_D2__GPIO_2_2	| MUX_PAD_CTRL(BUTTON_PAD_CTRL),
+	/* Labelled Search (mapped to Power under Android) */
+	MX6Q_PAD_NANDF_D3__GPIO_2_3	| MUX_PAD_CTRL(BUTTON_PAD_CTRL),
+	/* Home */
+	MX6Q_PAD_NANDF_D4__GPIO_2_4	| MUX_PAD_CTRL(BUTTON_PAD_CTRL),
+	/* Volume Down */
+	MX6Q_PAD_GPIO_19__GPIO_4_5	| MUX_PAD_CTRL(BUTTON_PAD_CTRL),
+	/* Volume Up */
+	MX6Q_PAD_GPIO_18__GPIO_7_13	| MUX_PAD_CTRL(BUTTON_PAD_CTRL),
+};
+
 static void setup_iomux_enet(void)
 {
 	gpio_direction_output(87, 0);  /* GPIO 3-23 */
@@ -267,11 +287,18 @@ int board_eth_init(bd_t *bis)
 	return 0;
 }
 
+static void setup_buttons(void)
+{
+	imx_iomux_v3_setup_multiple_pads(button_pads,
+					 ARRAY_SIZE(button_pads));
+}
+
 int board_early_init_f(void)
 {
-       setup_iomux_uart();
+	setup_iomux_uart();
+	setup_buttons();
 
-       return 0;
+	return 0;
 }
 
 int board_init(void)
@@ -292,3 +319,94 @@ int checkboard(void)
 
        return 0;
 }
+
+struct button_key {
+	char const	*name;
+	unsigned	gpnum;
+	char		ident;
+};
+
+static struct button_key const buttons[] = {
+	{"back",	GPIO_NUMBER(2, 2),	'B'},
+	{"home",	GPIO_NUMBER(2, 4),	'H'},
+	{"menu",	GPIO_NUMBER(2, 1),	'M'},
+	{"search",	GPIO_NUMBER(2, 3),	'S'},
+	{"volup",	GPIO_NUMBER(7, 13),	'V'},
+	{"voldown",	GPIO_NUMBER(4, 5),	'v'},
+};
+
+/*
+ * generate a null-terminated string containing the buttons pressed
+ * returns number of keys pressed
+ */
+static int read_keys(char *buf)
+{
+	int i, numpressed = 0;
+	for (i = 0; i < ARRAY_SIZE(buttons); i++) {
+		if (!gpio_get_value(buttons[i].gpnum))
+			buf[numpressed++] = buttons[i].ident;
+	}
+	buf[numpressed] = '\0';
+	return numpressed;
+}
+
+static int do_kbd(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	char envvalue[ARRAY_SIZE(buttons)+1];
+	int numpressed = read_keys(envvalue);
+	setenv("keybd", envvalue);
+	return numpressed == 0;
+}
+
+U_BOOT_CMD(
+	kbd, 1, 1, do_kbd,
+	"Tests for keypresses, sets 'keybd' environment variable",
+	"Returns 0 (true) to shell if key is pressed."
+);
+
+#ifdef CONFIG_PREBOOT
+static char const kbd_magic_prefix[] = "key_magic";
+static char const kbd_command_prefix[] = "key_cmd";
+
+static void preboot_keys(void)
+{
+	int numpressed;
+	char keypress[ARRAY_SIZE(buttons)+1];
+	numpressed = read_keys(keypress);
+	if (numpressed) {
+		char *kbd_magic_keys = getenv("magic_keys");
+		char *suffix;
+		/*
+		 * loop over all magic keys
+		 */
+		for (suffix = kbd_magic_keys; *suffix; ++suffix) {
+			char *keys;
+			char magic[sizeof(kbd_magic_prefix) + 1];
+			sprintf(magic, "%s%c", kbd_magic_prefix, *suffix);
+			keys = getenv(magic);
+			if (keys) {
+				if (!strcmp(keys, keypress))
+					break;
+			}
+		}
+		if (*suffix) {
+			char cmd_name[sizeof(kbd_command_prefix) + 1];
+			char *cmd;
+			sprintf(cmd_name, "%s%c", kbd_command_prefix, *suffix);
+			cmd = getenv(cmd_name);
+			if (cmd) {
+				setenv("preboot", cmd);
+				return;
+			}
+		}
+	}
+}
+#endif
+
+int misc_init_r(void)
+{
+#ifdef CONFIG_PREBOOT
+	preboot_keys();
+#endif
+	return 0;
+}

include/configs/mx6qsabrelite.h

@@ -42,6 +42,7 @@
 
 #define CONFIG_ARCH_CPU_INIT
 #define CONFIG_BOARD_EARLY_INIT_F
+#define CONFIG_MISC_INIT_R
 #define CONFIG_MXC_GPIO
 
 #define CONFIG_MXC_UART
@@ -110,6 +111,8 @@
 
 #define CONFIG_BOOTDELAY	       3
 
+#define CONFIG_PREBOOT                 ""
+
 #define CONFIG_LOADADDR			       0x10800000
 #define CONFIG_SYS_TEXT_BASE	       0x17800000