Provide functions to access arbitrary GPIO pins and vectors

This change adds utility functions which allow to read any GPIO pin,
as well as a vector of GPIO pin values.

As presented, these functions will be available to Sandy Bridge and
Ivy Bridge systems only.

There is no error checking: trying to read GPIO pin number which
exceeds actual number of pins will return zero, trying to read GPIO
which is not actually configured as such will return unpredictable
value.

When reading a GPIO pin vector, the pin numbers are passed in an
array, terminated by -1. For instance, to read GPIO pins 4, 2, 15 as a
three bit number GPIO4 * 4 + GPIO2 * 2 + GPIO15 * 1, one should pass
pointer to array of {4, 2, 15, -1}.

Change-Id: I042c12dbcb3c46d14ed864a48fc37d54355ced7d
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: http://review.coreboot.org/1049
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/southbridge/intel/bd82x6x/gpio.c

@@ -25,6 +25,8 @@
 #include "pch.h"
 #include "gpio.h"
 
+#define MAX_GPIO_NUMBER 75 /* zero based */
+
 void setup_pch_gpios(const struct pch_gpio_map *gpio)
 {
 	u16 gpiobase = pci_read_config16(PCH_LPC_DEV, GPIO_BASE) & 0xfffc;
@@ -63,3 +65,38 @@ void setup_pch_gpios(const struct pch_gpio_map *gpio)
 	if (gpio->set3.reset)
 		outl(*((u32*)gpio->set3.reset), gpiobase + GP_RST_SEL3);
 }
+
+int get_gpio(int gpio_num)
+{
+	static const int gpio_reg_offsets[] = {0xc, 0x38, 0x48};
+	u16 gpio_base = pci_read_config16(PCH_LPC_DEV, GPIO_BASE) & 0xfffc;
+	int index, bit;
+
+	if (gpio_num > MAX_GPIO_NUMBER)
+		return 0; /* Just ignore wrong gpio numbers. */
+
+	index = gpio_num / 32;
+	bit = gpio_num % 32;
+
+	return (inl(gpio_base + gpio_reg_offsets[index]) >> bit) & 1;
+}
+
+/*
+ * get a number comprised of multiple GPIO values. gpio_num_array points to
+ * the array of gpio pin numbers to scan, terminated by -1.
+ */
+unsigned get_gpios(const int *gpio_num_array)
+{
+	int gpio;
+	unsigned bitmask = 1;
+	unsigned vector = 0;
+
+	while (bitmask &&
+	       ((gpio = *gpio_num_array++) != -1)) {
+		vector <<= 1;
+		if (get_gpio(gpio))
+			vector |= bitmask;
+		bitmask <<= 1;
+	}
+	return vector;
+}

src/southbridge/intel/bd82x6x/gpio.h

@@ -150,4 +150,12 @@ struct pch_gpio_map {
 /* Configure GPIOs with mainboard provided settings */
 void setup_pch_gpios(const struct pch_gpio_map *gpio);
 
+/* get GPIO pin value */
+int get_gpio(int gpio_num);
+/*
+ * get a number comprised of multiple GPIO values. gpio_num_array points to
+ * the array of gpio pin numbers to scan, terminated by -1.
+ */
+unsigned get_gpios(const int *gpio_num_array);
+
 #endif