uboot移植rtc

uboot中可能会有需求提供rtc的支持目的达到uboot启动也能够进行墙上时间的显示和后面推断。大部分rtc支持的一个必要条件就是已经有i2c的支持。由于非常多的rtc是i2c接口控制的。uboot中i2c的移植在前一篇中已经提过。这里就仅仅做rtc的移植。这里选择了经常使用的一款rtc芯片pcf8653来分析。
第一步 开启支持的选项，
uboot/include/configs/mpc5200-common.h这个配置文件里开启了8653这个芯片的支持。
/*
* RTC configuration
*/

define CONFIG_RTC_PCF8563

define CONFIG_SYS_I2C_RTC_ADDR 0x51

这里定义了8653的开启配置和他的i2c的device id
第二步：uboot/drivers/rtc/Makefile
COBJS-$(CONFIG_RTC_PCF8563) += pcf8563.o
确定有这么一条，假设移植里面不存在的你就要自己加入了。

第三步 实现pcf8563.c 这个文件，这个就相当于新建立一个命令。可是这个命令还是uboot做了统一的。这样就能够方便使用者了。

/*
* (C) Copyright 2001
* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
*
* 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
*/

/*
* Date & Time support for Philips PCF8563 RTC
*/

/* #define DEBUG */

include

include

include

include

if defined(CONFIG_CMD_DATE)

static uchar rtc_read (uchar reg);
static void rtc_write (uchar reg, uchar val);

/* ————————————————————————- */

int rtc_get (struct rtc_time *tmp)
{
int rel = 0;
uchar sec, min, hour, mday, wday, mon_cent, year;

sec = rtc_read (0x02)-0x80;
min = rtc_read (0x03);
hour    = rtc_read (0x04);
mday    = rtc_read (0x05);
wday    = rtc_read (0x06);
mon_cent= rtc_read (0x07);
year    = rtc_read (0x08);

debug ( "Get RTC year: %02x mon/cent: %02x mday: %02x wday: %02x "
    "hr: %02x min: %02x sec: %02x
",
    year, mon_cent, mday, wday,
    hour, min, sec );
debug( "Alarms: wday: %02x day: %02x hour: %02x min: %02x
",
    rtc_read (0x0C),
    rtc_read (0x0B),
    rtc_read (0x0A),
    rtc_read (0x09) );

/*
if (sec & 0x80) {
puts (“xu Warning: RTC Low Voltage - date/time not reliable ”);
rel = -1;
}
*/
tmp->tm_sec = bcd2bin (sec & 0x7F);
tmp->tm_min = bcd2bin (min & 0x7F);
tmp->tm_hour = bcd2bin (hour & 0x3F);
tmp->tm_mday = bcd2bin (mday & 0x3F);
tmp->tm_mon = bcd2bin (mon_cent & 0x1F);
tmp->tm_year = bcd2bin (year) + ((mon_cent & 0x80) ?

2000 : 1900);
tmp->tm_wday = bcd2bin (wday & 0x07);
tmp->tm_yday = 0;
tmp->tm_isdst= 0;

debug( "Get DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d
",
    tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
    tmp->tm_hour, tmp->tm_min, tmp->tm_sec);

return rel;

}

int rtc_set (struct rtc_time *tmp)
{
uchar century;

debug ( "Set DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d
",
    tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
    tmp->tm_hour, tmp->tm_min, tmp->tm_sec);

rtc_write (0x08, bin2bcd(tmp->tm_year % 100));

century = (tmp->tm_year >= 2000) ? 0x80 : 0;
rtc_write (0x07, bin2bcd(tmp->tm_mon) | century);

rtc_write (0x06, bin2bcd(tmp->tm_wday));
rtc_write (0x05, bin2bcd(tmp->tm_mday));
rtc_write (0x04, bin2bcd(tmp->tm_hour));
rtc_write (0x03, bin2bcd(tmp->tm_min ));
rtc_write (0x02, bin2bcd(tmp->tm_sec ));

return 0;

}

void rtc_reset (void)
{

/* clear all control & status registers */
rtc_write (0x00, 0x00);
rtc_write (0x01, 0x00);
rtc_write (0x0D, 0x00);

/* clear Voltage Low bit */
rtc_write (0x02, rtc_read (0x02) & 0x7F);

/* reset all alarms */
rtc_write (0x09, 0x00);
rtc_write (0x0A, 0x00);
rtc_write (0x0B, 0x00);
rtc_write (0x0C, 0x00);

}

/* ————————————————————————- */

static uchar rtc_read (uchar reg)
{
return (i2c_reg_read (CONFIG_SYS_I2C_RTC_ADDR, reg));
}

static void rtc_write (uchar reg, uchar val)
{
i2c_reg_write (CONFIG_SYS_I2C_RTC_ADDR, reg, val);
}

endif

这俩能够看到
开启CONFIG_CMD_DATE 这个配置
在uboot/include/rtc.h中也是相同对rtc定义了几个标准函数：
int rtc_get (struct rtc_time *);
int rtc_set (struct rtc_time *);
void rtc_reset (void);

void GregorianDay (struct rtc_time *);
void to_tm (int, struct rtc_time *);
unsigned long mktime (unsigned int, unsigned int, unsigned int,
unsigned int, unsigned int, unsigned int);
我们上面的8563文件里也是相应的实现这几个函数。依照标准的參数配置回应标准的数据或者配置。

这里还要关心一个date.c的文件 这个文件实现了date命令unsigned long mktime (unsigned int, unsigned int, unsigned int,
unsigned int, unsigned int, unsigned int);