gpio: Add driver for Altera's PIO core

This driver may handle multiple PIO cores and thus needs to be
setup by calling the altera_pio_init() function within the early
board setup routine.

The driver comes with some extras, see below the copyleft header.

Signed-off-by: Joachim Foerster <joachim.foerster@missinglinkelectronics.com>
Tested-by: Thomas Chou <thomas@wytron.com.tw>
Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
diff --git a/board/altera/nios2-generic/custom_fpga.h b/board/altera/nios2-generic/custom_fpga.h
index f7f3853..fd3ec9a 100644
--- a/board/altera/nios2-generic/custom_fpga.h
+++ b/board/altera/nios2-generic/custom_fpga.h
@@ -51,6 +51,7 @@
 /* led_pio.s1 is a altera_avalon_pio */
 #define LED_PIO_BASE 0x82120870
 #define LED_PIO_WIDTH 8
+#define LED_PIO_RSTVAL 0x0
 
 /* high_res_timer.s1 is a altera_avalon_timer */
 #define CONFIG_SYS_TIMER_BASE 0x82120820
diff --git a/board/altera/nios2-generic/nios2-generic.c b/board/altera/nios2-generic/nios2-generic.c
index 49ef80d..0f88275 100644
--- a/board/altera/nios2-generic/nios2-generic.c
+++ b/board/altera/nios2-generic/nios2-generic.c
@@ -26,6 +26,7 @@
 #include <netdev.h>
 #include <mtd/cfi_flash.h>
 #include <asm/io.h>
+#include <asm/gpio.h>
 
 void text_base_hook(void); /* nop hook for text_base.S */
 
@@ -43,6 +44,13 @@
 int board_early_init_f(void)
 {
 	text_base_hook();
+#ifdef CONFIG_ALTERA_PIO
+#ifdef LED_PIO_BASE
+	altera_pio_init(LED_PIO_BASE, LED_PIO_WIDTH, 'o',
+			LED_PIO_RSTVAL, (1 << LED_PIO_WIDTH) - 1,
+			"led");
+#endif
+#endif
 #if defined(CONFIG_ENV_IS_IN_FLASH) && defined(CONFIG_ENV_ADDR)
 	early_flash_cmd_reset();
 #endif