add ref. crystal trimming.

board/std_conf.h

@@ -7,4 +7,24 @@
 #define vreg_init() default_vreg_init()
 #endif
 
+/* XTAL TUNE parameters */
+/* recommended defaults from the datasheet */
+
+/* Coarse tune: add 4pf */
+#ifndef CTUNE_4PF
+#define CTUNE_4PF 1
+#endif
+/* Coarse tune: add 0-7 pf */
+#ifndef CTUNE
+#define CTUNE 5
+#endif
+/* Fine tune: add FTUNE * 156fF (FTUNE is 4bits) */
+#ifndef FTUNE
+#define FTUNE 16
+#endif
+/* datasheet recommends taht you don't change this */
+#ifndef IBIAS
+#define IBIAS 0x1F
+#endif
+
 #endif