Hi Kevin, Thanks for the detailed response. I will try to find an un-solved bug to report next time ;) Thanks, Andrew Murray -----Original Message----- From: Kevin Hilman [mailto:khilman@xxxxxxxxxxxxxxxxxxx] Sent: 26 January 2010 16:32 To: Andrew Murray Cc: linux-omap@xxxxxxxxxxxxxxx Subject: Re: Issue with pm_debug? "Andrew Murray" <amurray@xxxxxxxxxxxxxx> writes: > Hello, > > I've been studying the power management support on the OMAP 35x EVM (Rev > G) and have noticed something which seems inconsistent with the > documentation. > > According to the elinux OMAP Power Management wiki page > (http://elinux.org/OMAP_Power_Management) - setting "sleep_while_idle" > to '1' and setting "enable_off_mode" and "voltage_off_while_idle" to '0' > in the debugfs should result in a kernel which will never hit 'off' > sleep states. > > However in this set up (with both ladder and menu governor) I've found > that in this state the C5 and C6 states are entered (according to > /sys/devices/system/cpu/cpu0/cpuidle/state[5/6]/time). However according > to the sources these states include the off state. > > Also the /debug/pm_debug/time indicates the off state wasn't reached. > Therefore is it just the case that the CPUIdle framework requested C5/6 > and the omap driver accepted by actually used another state? Yes, you're correct. (also, as an aside, /debug/pm_debug/count might be useful to you as well) > Is this incorrect behaviour? Yes, this is a bug. This is a known problem in that CPUidle statistics are wrong because we don't correctly report back to CPUidle the actual state that was entered when enable_off_mode==0. Sanjeev has proposed a patch for this and I have requested some changes from him: http://patchwork.kernel.org/patch/62533/ after the changes I have proposed, I plan to merge this into the PM branch. We have a similar issue with the recently posted OSWR support, and Sanjeev's patch will address both dynamic enable of off-mode and of OSWR. > Or is my understanding of power management implementation incorrect? > Any clarifications would be of great value. > > I've used the 'pm' branch in the khilman linux-omap-pm repository. (Is > this the most appropriate mailing list?) Yes, you're in the right place :) Thanks for reporting the problem and the thorough analysis. Kevin No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.432 / Virus Database: 271.1.1/2641 - Release Date: 01/25/10 19:36:00 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
