OMAP - Disabling/Delaying LCD Sleep Mode

Peter,

Depending on which build of Linux you are using you can try the following...

echo 0 > /sys/power/fb_timeout_value

BR,

Steve

Hi Steve,

Thanks for the quick reply.

I take it '0' disables the timeout, and any other number would change the value?  So I could set it to, say, 600?

I tried creating the file on the running OMAP board and got the following error:

root@omap3evm:~# ls -al /sys/power/fb_timeout_value
ls: /sys/power/fb_timeout_value: No such file or directory

... although that directory does exist:

root@omap3evm:~# ls -al /sys/power/
drwxr-xr-x    2 root     root            0 Sep 11 16:17 .
drwxr-xr-x   12 root     root            0 Jan  1  1970 ..
-rw-r--r--    1 root     root         4096 Sep 11 16:17 clocks_off_while_idle
-rw-r--r--    1 root     root         4096 Sep 11 16:17 enable_off_mode
-rw-r--r--    1 root     root         4096 Sep 11 16:17 sleep_while_idle
-rw-r--r--    1 root     root         4096 Sep 11 16:17 sr_vdd1_autocomp
-rw-r--r--    1 root     root         4096 Sep 11 16:17 sr_vdd2_autocomp
-rw-r--r--    1 root     root         4096 Sep 11 16:17 state
-rw-r--r--    1 root     root         4096 Sep 11 16:17 voltage_off_while_idle

Any idea why I'd see that error?

The linux build is:

root@omap3evm:~# uname -a
Linux omap3evm 2.6.29-rc3-omap1 #1 Mon Jan 11 14:44:57 EST 2010 armv7l unknown

CPU Info:

root@omap3evm:~# cat /proc/cpuinfo
Processor       : ARMv7 Processor rev 3 (v7l)
BogoMIPS        : 499.92
Features        : swp half thumb fastmult vfp edsp neon
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x1
CPU part        : 0xc08
CPU revision    : 3

Hardware        : OMAP3 EVM
Revision        : 0020
Serial          : 0000000000000000
root@omap3evm:~#

Looking at the loop mounted ramdisk, it looks like there is no '/sys/power' directory before boot.  Would it break things if the '/sys/power' directory were created in the ramdisk before boot?

Thanks again,

Peter Sienkewicz

Sorry.. the error I got was:

root@omap3evm:~# echo 0 > /sys/fb_timeout_value
-sh: can't create /sys/power/fb_timeout_value: nonexistent directory

Peter,

Sorry, I am now at the limit of my experience with this.

The /sys/ entries are not really file system files in the normal sense and are used to access hardware features in a somewhat flexible manner hence does not really exist in the ram disk per-se.

I don't know enough about the various builds to know which versions this should work on and which it doesn't. Obviously yours doesn't :(

Sorry I can't help much more.

BR,

Steve

Hi Steve,

Do you know where I could find a build of linux that would support this capability?  If I got the latest kernel/ramdisk from the TI website, would that be sufficient?

Or do you know any other way do go about doing the same thing, without creating /dev/power/fb_timeout_value?  By modifying the source directly?

Or finally, if you're not quite sure moving forward, do you know of anybody who's done this before that you could refer me to?

Thanks again,

Peter

Hi Steve,

Another thought.. if I disabled Power Management in the kernel, would that disbale this behavour?

Finally.. just wanted to thank you for your help on all this ... much appreciated.

Peter

Peter,

You could try disabling power management if you don't explicitly need it.

I will see if I can find out more information for you, but the Linux builds are not really my forte.

You are more than welcome :) Hopefully I can actually be useful at the end of all this !!

BR,

Steve

Hi Steve,

I tried disabling 'power management' in the kernal, and after doing so, the LCD still goes into sleep mode. 

Please let me know if you find any other information on the matter.

Thanks again!

Peter

Peter,

OK, try this...

100 > /sys/devices/platform/omapfb/sleep_timeout

which should change the timeout from the default of 20 seconds to 100 seconds.

Supposedly this is described in the Migration Guide which should be included somewhere in the PSP release. I can't confirm this at the moment since I have not looked at the release.

Steve K. gave me this answer, so thanks Steve :)

BR,

Stev

Steve,

You forgot the echo in front of the 100

echo 100 >/sys/devices/platform/omapfb/sleep_timeout

Would set the timeout to 100 seconds instead of the default 20 secondis.

Steve K.

ooops, should pay more attention to cut and paste !! :)

Hi Steve,

That worked.. Thanks a million!!!

Regards

Peter Sienkewicz

Excellent.

I can go home now that I have actually achieved something :)

BR,

Steve