AM1808 - Date/Time Initialization

Dan Tesone

Other Parts Discussed in Thread: OMAP-L138, AM1808

Can someone enlighten me on how to go about initializing the Date/Time such that it persists over "reboots"?
I have attempted to use the linux Date command followed by a hwclock -w command as follows:

date -s "2011-09-26 12:41:00"
hwclock -w

But this does not do the trick. It seems as though whenever I reboot, the date/time reported is via running the "date" command starts at:
Fri Dec 11 11:54:00 UTC 2009

I do see the following line during boot:
omap_rtc omap_rtc: setting system clock to 2000-01-01 00:00:00 UTC (946684800)

My Kernel configuration options have "Set system time from RTC on startup and resume" enabled for Real Time Clock.
Also - I am using a RAM disk that is loaded from NAND when reboot takes place.

Anyone have any ideas?

over 14 years ago

0 Sudhakar Rajashekhara over 14 years ago

TI__Expert 5170 points

Hi,

On few OMAP-L138 platforms, it was observed that RTC is not working properly. Please try the patch at http://arago-project.org/git/projects/?p=linux-davinci.git;a=commit;h=72a745b1ca171314e4679bd2190284bda07667bc and let me know whether this resolves the issue.

Regards, Sudhakar

0 Dan Tesone over 14 years ago in reply to Sudhakar Rajashekhara

Intellectual 450 points

Hi Sudhakar - thanks for your reply. I downloaded the rtc-omap.c file from the link you provided, Cross-compiled my Kernel and reflashed my NAND uImage. When I boot, I get the same behviour I original received. Here is the sequence of steps I went through:

> date -s "2011-09-29 08:55:00" <enter>
Thu Sep 28 08:55:00 UTC 2011
> hwclock -w <enter>
> hwclock -r <enter>
Sat Jan 1 00:00:00 200 0.000000 seconds

Is hwclock -w the call I should be making? Performing a read afterward does not seem to indicate the write call did anything. Then I perform a reboot...but I get the same - Date reverts back to Fri Dec 11 11:54:00 UTC 2009 (which I really don't understand).
Is there a uBoot setting I need set?
Thanks for your help.

0 Sudhakar Rajashekhara over 14 years ago in reply to Dan Tesone

TI__Expert 5170 points

Hi,

Have you installed a battery such that the time is retained across restarts? By default OMAP-L138 EVM does not come with any battery.

Regards, Sudhakar

0 Dan Tesone over 14 years ago in reply to Sudhakar Rajashekhara

Intellectual 450 points

Hi Sudhakar,

Thanks for your reply - that must be the case (as obvious as it should have been) - I am working with a custom board with the same AM1808 that is on the OMAP-L138 EVM and our board also does not have a battery. Although currently I have no way to confirm this will totally fix the problem, I feel reasonably assured it will - so I will mark your last reply as the solution. Thanks for pointing out what I should have been asking myself ... "when the power is off how will the internal clock keep time without a battery?".

Processors

Processors forum

AM1808 - Date/Time Initialization