i2c, bootcount: add support for bootcounter on i2c devices

add support for bootcounter on an i2c device. And add a
README for all bootcounter options.

Signed-off-by: Heiko Schocher <hs@denx.de>

README

@@ -2855,6 +2855,26 @@ CBFS (Coreboot Filesystem) support
 		The signing part is build into mkimage regardless of this
 		option.
 
+- bootcount support:
+		CONFIG_BOOTCOUNT_LIMIT
+
+		This enables the bootcounter support, see:
+		http://www.denx.de/wiki/DULG/UBootBootCountLimit
+
+		CONFIG_AT91SAM9XE
+		enable special bootcounter support on at91sam9xe based boards.
+		CONFIG_BLACKFIN
+		enable special bootcounter support on blackfin based boards.
+		CONFIG_SOC_DA8XX
+		enable special bootcounter support on da850 based boards.
+		CONFIG_BOOTCOUNT_RAM
+		enable support for the bootcounter in RAM
+		CONFIG_BOOTCOUNT_I2C
+		enable support for the bootcounter on an i2c (like RTC) device.
+			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
+			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
+						    the bootcounter.
+			CONFIG_BOOTCOUNT_ALEN = address len
 
 - Show boot progress:
 		CONFIG_SHOW_BOOT_PROGRESS

drivers/bootcount/Makefile

@@ -9,3 +9,4 @@ obj-$(CONFIG_SOC_DA8XX)		+= bootcount_davinci.o
 obj-$(CONFIG_BOOTCOUNT_AM33XX)	+= bootcount_davinci.o
 obj-$(CONFIG_BOOTCOUNT_RAM)	+= bootcount_ram.o
 obj-$(CONFIG_BOOTCOUNT_ENV)	+= bootcount_env.o
+obj-$(CONFIG_BOOTCOUNT_I2C)	+= bootcount_i2c.o

drivers/bootcount/bootcount_i2c.c

@@ -0,0 +1,44 @@
+/*
+ * (C) Copyright 2013
+ * Heiko Schocher, DENX Software Engineering, hs@denx.de.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <bootcount.h>
+#include <linux/compiler.h>
+#include <i2c.h>
+
+#define BC_MAGIC	0xbc
+
+void bootcount_store(ulong a)
+{
+	unsigned char buf[3];
+	int ret;
+
+	buf[0] = BC_MAGIC;
+	buf[1] = (a & 0xff);
+	ret = i2c_write(CONFIG_SYS_I2C_RTC_ADDR, CONFIG_SYS_BOOTCOUNT_ADDR,
+		  CONFIG_BOOTCOUNT_ALEN, buf, 2);
+	if (ret != 0)
+		puts("Error writing bootcount\n");
+}
+
+ulong bootcount_load(void)
+{
+	unsigned char buf[3];
+	int ret;
+
+	ret = i2c_read(CONFIG_SYS_I2C_RTC_ADDR, CONFIG_SYS_BOOTCOUNT_ADDR,
+		       CONFIG_BOOTCOUNT_ALEN, buf, 2);
+	if (ret != 0) {
+		puts("Error loading bootcount\n");
+		return 0;
+	}
+	if (buf[0] == BC_MAGIC)
+		return buf[1];
+
+	bootcount_store(0);
+
+	return 0;
+}