On Tue, 21 May 2013 03:21:30 +0400 Sergey Yanovich <ynv...@gmail.com> wrote:
> This chip has a control register and can prevent altering saved clock.
> Without this patch we could have:
> ----8<----
> (arm)root@pac14:~# date
> Tue May 21 03:08:27 MSK 2013
> (arm)root@pac14:~# /etc/init.d/hwclock.sh show
> Tue May 21 11:13:58 2013 -0.067322 seconds
> (arm)root@pac14:~# /etc/init.d/hwclock.sh stop
> [info] Saving the system clock.
> [info] Hardware Clock updated to Tue May 21 03:09:01 MSK 2013.
> (arm)root@pac14:~# /etc/init.d/hwclock.sh show
> Tue May 21 11:14:15 2013 -0.624272 seconds
> ----8<----
>
> ...
>
> --- a/drivers/rtc/rtc-ds1302.c
> +++ b/drivers/rtc/rtc-ds1302.c
> @@ -23,8 +23,12 @@
> #define RTC_CMD_READ 0x81 /* Read command */
> #define RTC_CMD_WRITE 0x80 /* Write command */
>
> +#define RTC_CMD_WRITE_ENABLE 0x00 /* Write enable */
> +#define RTC_CMD_WRITE_DISABLE 0x80 /* Write disable */
> +
> #define RTC_ADDR_RAM0 0x20 /* Address of RAM0 */
> #define RTC_ADDR_TCR 0x08 /* Address of trickle charge register */
> +#define RTC_ADDR_CTRL 0x07 /* Address of control register
> */
> #define RTC_ADDR_YEAR 0x06 /* Address of year register */
> #define RTC_ADDR_DAY 0x05 /* Address of day of week
> register */
> #define RTC_ADDR_MON 0x04 /* Address of month register */
> @@ -313,6 +317,7 @@ static int __init ds1302_rtc_probe(struct platform_device
> *pdev)
> return PTR_ERR(rtc);
>
> platform_set_drvdata(pdev, rtc);
> + ds1302_writebyte(RTC_ADDR_CTRL, RTC_CMD_WRITE_ENABLE);
>
> return 0;
> }
> @@ -321,6 +326,7 @@ static int ds1302_rtc_remove(struct platform_device *pdev)
> {
> struct rtc_device *rtc = platform_get_drvdata(pdev);
>
> + ds1302_writebyte(RTC_ADDR_CTRL, RTC_CMD_WRITE_DISABLE);
> rtc_device_unregister(rtc);
> platform_set_drvdata(pdev, NULL);
ds1302_rtc_remove() no longer exists in my tree - it got whittled away
to nothing by
http://ozlabs.org/~akpm/mmots/broken-out/rtc-rtc-ds1302-remove-unnecessary-platform_set_drvdata.patch
and
http://ozlabs.org/~akpm/mmots/broken-out/drivers-rtc-rtc-ds1302c-remove-empty-function.patch
Perhaps it should be re-added for this?
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