uboot中rtc顶层分析

uboot一般不会要求开启rtc，不过还是支持rtc以备特殊需求的。底层驱动移植前面两篇已经介绍，这里介绍顶层的调用过程。顶层在uboot/common/cmd_date.c

/*
* (C) Copyright 2001
* Wolfgang Denk, DENX Software Engineering, [e-mail].
*
* 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
*/

/*
* RTC, Date & Time support: get and set date & time
*/

include

include

include

include

ifdef CONFIG_RELOC_FIXUP_WORKS

define RELOC(a) a

else

define RELOC(a) ((typeof(a))((unsigned long)(a) + gd->reloc_off))

endif

int mk_date (char , struct rtc_time );

int do_date (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
struct rtc_time tm;
int rcode = 0;
int old_bus;

/* switch to correct I2C bus */old_bus = I2C_GET_BUS();I2C_SET_BUS(CONFIG_SYS_RTC_BUS_NUM);switch (argc) {case 2:         /* set date & time */    if (strcmp(argv[1],"reset") == 0) {        puts ("Reset RTC...\n");        rtc_reset ();    } else {        /* initialize tm with current time */        rcode = rtc_get (&tm);        if(!rcode) {            /* insert new date & time */            if (mk_date (argv[1], &tm) != 0) {                puts ("## Bad date format\n");                break;            }            /* and write to RTC */            rcode = rtc_set (&tm);            if(rcode)                puts("## Set date failed\n");        } else {            puts("## Get date failed\n");        }    }    /* FALL TROUGH */case 1:         /* get date & time */    rcode = rtc_get (&tm);    if (rcode) {        puts("## Get date failed\n");        break;    }    printf ("Date: %4d-%02d-%02d (%sday)    Time: %2d:%02d:%02d\n",        tm.tm_year, tm.tm_mon, tm.tm_mday,        (tm.tm_wday<0 || tm.tm_wday>6) ?            "unknown " : RELOC(weekdays[tm.tm_wday]),        tm.tm_hour, tm.tm_min, tm.tm_sec);    break;default:    cmd_usage(cmdtp);    rcode = 1;}/* switch back to original I2C bus */I2C_SET_BUS(old_bus);return rcode;

}

/*
* simple conversion of two-digit string with error checking
*/
static int cnvrt2 (char *str, int *valp)
{
int val;

if ((*str < '0') || (*str > '9'))    return (-1);val = *str - '0';++str;if ((*str < '0') || (*str > '9'))    return (-1);*valp = 10 * val + (*str - '0');return (0);

}

/*
* Convert date string: MMDDhhmm[[CC]YY][.ss]
*
* Some basic checking for valid values is done, but this will not catch
* all possible error conditions.
*/
int mk_date (char *datestr, struct rtc_time *tmp)
{
int len, val;
char *ptr;

ptr = strchr (datestr,'.');len = strlen (datestr);/* Set seconds */if (ptr) {    int sec;    *ptr++ = '\0';    if ((len - (ptr - datestr)) != 2)        return (-1);    len = strlen (datestr);    if (cnvrt2 (ptr, &sec))        return (-1);    tmp->tm_sec = sec;} else {    tmp->tm_sec = 0;}if (len == 12) {        /* MMDDhhmmCCYY */    int year, century;    if (cnvrt2 (datestr+ 8, &century) ||        cnvrt2 (datestr+10, &year) ) {        return (-1);    }    tmp->tm_year = 100 * century + year;} else if (len == 10) {     /* MMDDhhmmYY   */    int year, century;    century = tmp->tm_year / 100;    if (cnvrt2 (datestr+ 8, &year))        return (-1);    tmp->tm_year = 100 * century + year;}switch (len) {case 8:         /* MMDDhhmm */    /* fall thru */case 10:        /* MMDDhhmmYY   */    /* fall thru */case 12:        /* MMDDhhmmCCYY */    if (cnvrt2 (datestr+0, &val) ||        val > 12) {        break;    }    tmp->tm_mon  = val;    if (cnvrt2 (datestr+2, &val) ||        val > ((tmp->tm_mon==2) ? 29 : 31)) {        break;    }    tmp->tm_mday = val;    if (cnvrt2 (datestr+4, &val) ||        val > 23) {        break;    }    tmp->tm_hour = val;    if (cnvrt2 (datestr+6, &val) ||        val > 59) {        break;    }    tmp->tm_min  = val;    /* calculate day of week */    GregorianDay (tmp);    return (0);default:    break;}return (-1);

}

/*****************************************/

U_BOOT_CMD(
date, 2, 1, do_date,
“get/set/reset date & time”,
“[MMDDhhmm[[CC]YY][.ss]]\ndate reset\n”
” - without arguments: print date & time\n”
” - with numeric argument: set the system date & time\n”
” - with ‘reset’ argument: reset the RTC”
);
这里反向分析：
第一步是注册 date命令
U_BOOT_CMD(
date, 2, 1, do_date,
“get/set/reset date & time”,
“[MMDDhhmm[[CC]YY][.ss]]\ndate reset\n”
” - without arguments: print date & time\n”
” - with numeric argument: set the system date & time\n”
” - with ‘reset’ argument: reset the RTC”
);
这个命令就是rtc的控制命令了 调用的函数是 do_date
int do_date (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
可以看到这命令是调用了rtc里面注册的rtc_reset、rtc_get、rtc_set
分为case1 ：获取当年的时间
case2 设置时间；
时间转换函数mk_date 可以将我们输入的字符串转化成为时间的年月日 供rtc_set 配置下去去