System76 EC console support

Change-Id: I04c2aeb19d780a7c6638b502192fa9f569e32e94

src/drivers/system76_ec/system76_ec.c

@@ -0,0 +1,49 @@
+#include <arch/io.h>
+#include <console/system76_ec.h>
+#include <delay.h>
+
+#define SYSTEM76_EC_BASE 0x0E00
+
+static uint8_t system76_ec_read(uint8_t addr) {
+    return inb(SYSTEM76_EC_BASE + (uint16_t)addr);
+}
+
+static void system76_ec_write(uint8_t addr, uint8_t data) {
+    outb(data, SYSTEM76_EC_BASE + (uint16_t)addr);
+}
+
+int system76_ec_print(uint8_t *buf, size_t len) {
+    size_t i;
+    for (i=0; i < len;) {
+        if (system76_ec_read(0) == 0) {
+            size_t j;
+            for (j=0; (i < len) && ((j + 4) < 256); i++, j++) {
+                system76_ec_write((uint8_t)(j + 4), buf[i]);
+            }
+            // Flags
+            system76_ec_write(2, 0);
+            // Length
+            system76_ec_write(3, (uint8_t)j);
+            // Command
+            system76_ec_write(0, 4);
+            // Wait for command completion, for up to 1 second
+            int timeout;
+            for (timeout = 1000000; timeout > 0; timeout--) {
+                if (system76_ec_read(0) == 0) break;
+                udelay(1);
+            }
+            if (timeout == 0) {
+                // Error: timeout occured
+                return -1;
+            }
+            if (system76_ec_read(1) != 0) {
+                // Error: command failed
+                return -1;
+            }
+        } else {
+            // Error: command is already running
+            return -1;
+        }
+    }
+    return (int)i;
+}