rpi gpio: Rework GPIO support

* GPIO calls now simplier and more correct
* Set UART pins to AUX0 mode

src/system/boot/platform/raspberrypi_arm/gpio.cpp

@@ -4,22 +4,108 @@
  *
  * Authors:
  *		Alexander von Gluck, [email protected]
+ *		Gordon Henderson, [email protected]
  */
 
 
 #include "gpio.h"
 
 
+//  Define the shift up for the 3 bits per pin in each GPFSEL port
+static uint8_t
+kGPIOToShift[] =
+{
+	0, 3, 6, 9, 12, 15, 18, 21, 24, 27,
+	0, 3, 6, 9, 12, 15, 18, 21, 24, 27,
+	0, 3, 6, 9, 12, 15, 18, 21, 24, 27,
+	0, 3, 6, 9, 12, 15, 18, 21, 24, 27,
+	0, 3, 6, 9, 12, 15, 18, 21, 24, 27,
+};
+
+
+//  Map a BCM_GPIO pin to it's control port. (GPFSEL 0-5)
+static uint8_t
+kGPIOToGPFSEL[] =
+{
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+	2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+	3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+	4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+	5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
+};
+
+
+// (Word) offset to the GPIO Set registers for each GPIO pin
+static uint8_t
+kGPIOToGPSET[] =
+{
+	7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+	7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+	8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+	8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+};
+
+// (Word) offset to the GPIO Clear registers for each GPIO pin
+static uint8_t
+kGPIOToGPCLR[] =
+{
+	10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
+	10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
+	11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
+	11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
+};
+
+
+/*!
+ * At GPIO (base) (pin) state set (value)
+ */
+void
+gpio_write(addr_t base, int pin, bool value)
+{
+	volatile addr_t *gpio = (addr_t*)base;
+
+	if (value == 1)
+		*(gpio + kGPIOToGPSET[pin]) = 1 << pin;
+	else
+		*(gpio + kGPIOToGPCLR[pin]) = 1 << pin;
+}
+
+
+/*!
+ * At GPIO (base) (pin) set mode (mode)
+ */
+void
+gpio_mode(addr_t base, int pin, int mode)
+{
+	int sel = kGPIOToGPFSEL[pin];
+	int shift = kGPIOToShift[pin];
+
+	volatile addr_t *gpio = (addr_t*)base + sel;
+
+	if (mode == GPIO_IN)
+		*gpio = (*gpio & ~(7 << shift));
+	else if (mode == GPIO_OUT)
+		*gpio = (*gpio & ~(7 << shift)) | (1 << shift);
+	else
+		*gpio = (*gpio & ~(7 << shift)) | (mode << shift);
+}
+
+
 void
 gpio_init()
 {
-	// Set up pointer to Raspberry Pi GPIO base
-	gGPIOBase = (volatile unsigned *)GPIO_BASE;
-
-	// Take control of ok led and general use pins
+	// ** Take control of ok led, and general use pins
 	int pin = 0;
-	for (pin = 16; pin <= 25; pin++) {
-		GPIO_IN(pin);
-		GPIO_OUT(pin);
-	}
+	for (pin = 16; pin <= 25; pin++)
+		gpio_mode(GPIO_BASE, pin, GPIO_OUT);
+
+	// ** Prepare UART pins for serial communication
+	// Set alternate function 0 on UART pins
+	gpio_mode(GPIO_BASE, 14, GPIO_ALT0);
+	gpio_mode(GPIO_BASE, 15, GPIO_ALT0);
+
+	// Pull UART pins to initial state low
+	gpio_write(GPIO_BASE, 14, 0);
+	gpio_write(GPIO_BASE, 15, 0);
 }

src/system/boot/platform/raspberrypi_arm/gpio.h

@@ -9,24 +9,30 @@
 #define _SYSTEM_BOOT_PLATFORM_PI_GPIO_H
 
 
+#include <SupportDefs.h>
+
 #include <arch/arm/bcm2708.h>
 
 
-// Macros for easy GPIO pin access in loader
-#define GPIO_IN(g) *(gGPIOBase + ((g)/10)) &= ~(7<<(((g)%10)*3))
-#define GPIO_OUT(g) *(gGPIOBase + ((g)/10)) |=  (1<<(((g)%10)*3))
-#define GPIO_SET(g) *(gGPIOBase + 7) = (1<<g)
-#define GPIO_CLR(g) *(gGPIOBase + 10) = (1<<g)
+#define GPIO_IN		0
+#define GPIO_OUT	1
+#define GPIO_ALT0	4
+#define GPIO_ALT1	5
+#define GPIO_ALT2	6
+#define GPIO_ALT3	7
+#define GPIO_ALT4	3
+#define GPIO_ALT5	2
 
 
-volatile unsigned *gGPIOBase;
-
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 
+void gpio_write(addr_t base, int pin, bool value);
+void gpio_mode(addr_t base, int pin, int mode);
+
 void gpio_init();
 
 

src/system/boot/platform/raspberrypi_arm/start.c

@@ -108,7 +108,7 @@ pi_start(void)
 	gpio_init();
 
 	// Flick on "OK" led
-	GPIO_CLR(16);
+	gpio_write(GPIO_BASE, 16, 0);
 
 	mmu_init();
 	serial_init();

src/system/kernel/arch/arm/uart_pl011.cpp

@@ -60,6 +60,7 @@ void
 uart_pl011_init_early(void)
 {
 	// Perform special hardware UART configuration
+	// Raspberry Pi: Early setup handled by gpio_init in platform code
 }