Why is the e500v2 core not using cpuidle?

[Scott Wood]

On 02/07/2013 06:19:25 AM, Thomas Waldecker wrote:
> Hi Scott,
> 
> I measured the power consumption of the whole system on the tqmp2020  
> ( http://tq-group.com/tqmp2020 )
> with a QorIQ P2020.
> 
> Kernel:
> root at generic-powerpc-e500v2:/sys/power# uname -a
> Linux generic-powerpc-e500v2 3.7.0-rc8-00004-g6e93414 #4 SMP Tue Dec  
> 11 08:53:23 CET 2012 ppc GNU/Linux
> root at generic-powerpc-e500v2:/sys/power# cat /etc/issue
> ELDK 5.2.1 \n \l
> 
> In idle using doze I got:
> 545mA, 18V => 9.81W
> 
> In idle using nap I got:
> 500mA, 18V => 9W
> 
> That's a difference of 0.81W,
> 0.81W/9.81W = 0.083 (8.3 %)

Thanks.

> > The only way you'll get into sleep mode is through /sys/power/state.
> 
> How can I use this interface?
> 
> root at generic-powerpc-e500v2:/sys/power# ls -la
> total 0
> drwxr-xr-x  2 root root    0 Feb  1 15:39 .
> dr-xr-xr-x 12 root root    0 Feb  1 15:19 ..
> -rw-r--r--  1 root root 4096 Feb  1 15:39 state
> root at generic-powerpc-e500v2:/sys/power# cat state
> root at generic-powerpc-e500v2:/sys/power# echo "sleep" > state
> -sh: echo: write error: Function not implemented
> root at generic-powerpc-e500v2:/sys/power# echo 0 > state
> -sh: echo: write error: Function not implemented
> root at generic-powerpc-e500v2:/sys/power#

Make sure that CONFIG_FSL_PMC is enabled, and that you have a pmc node  
in the device tree.  You'll only have standby, not sleep.  mpc8536 and  
p1022 can support what the chip calls "deep sleep" and is exposed as  
"sleep" rather than "standby", but it doesn't look like the code for  
that has made it into mainline Linux yet.

-Scott