libubb/mmcclk.c: helper functions for selecting and configuring the MMC bus clock

Experimental.

libubb/include/ubb/mmcclk.h

@@ -0,0 +1,36 @@
+/*
+ * include/ubb/mmcclk.h -  Calculate MMC bus clock speed
+ *
+ * Written 2013 by Werner Almesberger
+ * Copyright 2013 Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef UBB_MMCCLK_H
+#define UBB_MMCCLK_H
+
+#include <stdint.h>
+
+
+#define	BEN_SYS_CLK_HZ		336000000
+
+
+struct mmcclk {
+	int sys_clk_hz;		/* system clock speed in Hz */
+	double bus_clk_hz;	/* MMC bus clock in Hz */
+	uint32_t clkdiv;	/* MSC controller clock */
+	uint32_t clkrt;		/* bus clock divider */
+};
+
+
+void mmcclk_first(struct mmcclk *dsc, int sys_clk_hz);
+int mmcclk_next(struct mmcclk *dsc);
+
+void mmcclk_start(struct mmcclk *dsc);
+void mmcclk_stop(void);
+
+#endif /* !UBB_MMCCLK_H */