omap4: calculate EMIF register values

Calculate EMIF register values based on AC timing parameters
from the SDRAM datasheet and the DDR frequency rather than
using the hard-coded values.

For a new board the user doen't have to go through the tedious
process of calculating the register values. Instead, just
provide the AC timings from the device data sheet as input
and the driver will automatically calculate the register values.

Signed-off-by: Aneesh V <aneesh@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>

2 files changed, 58 insertions, 0 deletions

diff --git a/arch/arm/cpu/armv7/omap-common/Makefile b/arch/arm/cpu/armv7/omap-common/Makefile
index dc01ee5d3..8f698f841 100644
--- a/arch/arm/cpu/armv7/omap-common/Makefile
+++ b/arch/arm/cpu/armv7/omap-common/Makefile
@@ -28,6 +28,7 @@ LIB	= $(obj)libomap-common.o
 SOBJS	:= reset.o
 
 COBJS	:= timer.o
+COBJS	+= utils.o
 
 SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(SOBJS) $(COBJS))
diff --git a/arch/arm/cpu/armv7/omap-common/utils.c b/arch/arm/cpu/armv7/omap-common/utils.c
new file mode 100644
index 000000000..ea935da45
--- /dev/null
+++ b/arch/arm/cpu/armv7/omap-common/utils.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2011 Linaro Limited
+ * Aneesh V <aneesh@ti.com>
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+#include <common.h>
+static void do_cancel_out(u32 *num, u32 *den, u32 factor)
+{
+	while (1) {
+		if (((*num)/factor*factor == (*num)) &&
+		   ((*den)/factor*factor == (*den))) {
+			(*num) /= factor;
+			(*den) /= factor;
+		} else
+			break;
+	}
+}
+
+/*
+ * Cancel out the denominator and numerator of a fraction
+ * to get smaller numerator and denominator.
+ */
+void cancel_out(u32 *num, u32 *den, u32 den_limit)
+{
+	do_cancel_out(num, den, 2);
+	do_cancel_out(num, den, 3);
+	do_cancel_out(num, den, 5);
+	do_cancel_out(num, den, 7);
+	do_cancel_out(num, den, 11);
+	do_cancel_out(num, den, 13);
+	do_cancel_out(num, den, 17);
+	while ((*den) > den_limit) {
+		*num /= 2;
+		/*
+		 * Round up the denominator so that the final fraction
+		 * (num/den) is always <= the desired value
+		 */
+		*den = (*den + 1) / 2;
+	}
+}