设备树学习之（六）RTC

转载自：http://blog.csdn.net/lizuobin2/article/details/54564621

开发板：tiny4412SDK + S702 + 4GB Flash

要移植的内核版本：Linux-4.4.0 （支持device tree）

u-boot版本：友善之臂自带的 U-Boot 2010.12

busybox版本：busybox 1.25

目标：

Linux4.4 中已经对 tiny4412 rtc 有了支持，但是使能设备树之后启动报错，简单修改，使 rtc 正常工作。

设备树：

rtc: rtc@10070000 {
compatible = "samsung,s3c6410-rtc";
reg = <0x10070000 0x100>;
interrupt-parent = <&pmu_system_controller>;//注释掉此行
interrupts = <0 44 0>, <0 45 0>;
clocks = <&clock CLK_RTC>;
clock-names = "rtc";
status = "disabled";
};

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启动错误信息：

[    2.193630] s3c-rtc 10070000.rtc: failed to find rtc source clock
[    2.198950] s3c-rtc: probe of 10070000.rtc failed with error -2

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[/code]

简单修改：

修改：driver/rtc/rtc-s3c.c
注释掉以下代码
/*
if (info->data->needs_src_clk) {
info->rtc_src_clk = devm_clk_get(&pdev->dev, "rtc_src");
if (IS_ERR(info->rtc_src_clk)) {
dev_err(&pdev->dev,
"failed to find rtc source clock\n");
clk_disable_unprepare(info->rtc_clk);
return PTR_ERR(info->rtc_src_clk);
}
clk_prepare_enable(info->rtc_src_clk);
}
*/
或者修改：
static struct s3c_rtc_data const s3c6410_rtc_data = {
.max_user_freq      = 32768,
.needs_src_clk      = true, //修改为false
.irq_handler        = s3c6410_rtc_irq,
.set_freq           = s3c6410_rtc_setfreq,
.enable_tick        = s3c6410_rtc_enable_tick,
.save_tick_cnt      = s3c6410_rtc_save_tick_cnt,
.restore_tick_cnt   = s3c6410_rtc_restore_tick_cnt,
.enable         = s3c24xx_rtc_enable,
.disable        = s3c6410_rtc_disable,
};

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[/code]

linux 下更改系统时间：

date: invalid option -- 'h'
BusyBox v1.25.0 (2016-12-16 21:42:21 ULAT) multi-call binary.

Usage: date [OPTIONS] [+FMT] [TIME]

Display time (using +FMT), or set time

[-s,--set] TIME Set time to TIME
-u,--utc        Work in UTC (don't convert to local time)
-R,--rfc-2822   Output RFC-2822 compliant date string
-I[SPEC]        Output ISO-8601 compliant date string
SPEC='date' (default) for date only,
'hours', 'minutes', or 'seconds' for date and
time to the indicated precision
-r,--reference FILE     Display last modification time of FILE
-d,--date TIME  Display TIME, not 'now'
-D FMT          Use FMT for -d TIME conversion

Recognized TIME formats:
hh:mm[:ss]
[YYYY.]MM.DD-hh:mm[:ss]
YYYY-MM-DD hh:mm[:ss]
[[[[[YY]YY]MM]DD]hh]mm[.ss]
'date TIME' form accepts MMDDhhmm[[YY]YY][.ss] instead
date -s 2017-01-01
date -s 22:50:00

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[/code]

系统时间和硬件rtc的同步：

/ # hwclock -h
hwclock: invalid option -- 'h'
BusyBox v1.25.0 (2016-12-16 21:42:21 ULAT) multi-call binary.

Usage: hwclock [-r|--show] [-s|--hctosys] [-w|--systohc] [-t|--systz] [-l|--loc]

Query and set hardware clock (RTC)

-r      Show hardware clock time
-s      Set system time from hardware clock
-w      Set hardware clock from system time
-t      Set in-kernel timezone, correct system time
if hardware clock is in local time
-u      Assume hardware clock is kept in UTC
-l      Assume hardware clock is kept in local time
-f FILE Use specified device (e.g. /dev/rtc2)

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[/code]