Thanks for the pointer to the pm-wip-opp branch - I'm not familiar with the new opp layer so I'll take a look. I currently have no need to directly control the VDD2 frequency - though after browsing the code I was interested to find out if my understanding was correct or if I was missing something. I guess if there was a need the framework is already in place such that a kernel module could simply use the API. I apologise for all these questions - I've spent the past couple of weeks getting to grips with power management in the OMAP and wanted to understand the level of kernel support for the various features. Though I do have a final question: I understood OPP's to be pairs of voltage and frequency and there were only a certain number of discrete OPP steps for each domain, i.e. 5 for VDD1, 2/3 for VDD2. However from reading the TPM (and the fact that the L3 frequency differs to the white paper documentation) it suggests that voltage/frequency can be set to any value. Thus leading me to wonder why there aren't more OPP sets? Or is it the case that the chosen sets represent a broad range of power-efficient OPPs? I've noticed that other than using the debugfs there is no way for a user to configure sleep_when_idle, enable_off_mode, voltage_off_when_idle. Do you think it would be worthwhile to add these options to the KConfigs? I'd be happy to make these modifications if so. :) Many Thanks, Andrew Murray -----Original Message----- From: Nishanth Menon [mailto:nm@xxxxxx] Sent: 26 January 2010 20:41 To: Andrew Murray Cc: linux-omap@xxxxxxxxxxxxxxx Subject: Re: PM: VDD2 OPPs Andrew Murray had written, on 01/26/2010 02:34 PM, the following: > Hello, > > With regards to the OMAP2 (or at least the 3530 EVM) -the TRM and > various whitepapers suggest that they are 3 OPP levels available for > VDD2 (L3). However, from looking at the sources (linux-omap-pm / pm > branch) it seems that only 2 OPP levels are supported (@166Mhz and > @83Mhz) and used. I also notice that these rates are different to those > in a whitepaper (166, 100 and 41.5). Is there any particular reason why on OMAP34/35xx, I believe it should be s/100/83/. > only 2 OPPs are used? to my knowledge 41.5Mhz is not known to provide any performance benefits. you can also see [1] and add 41.5 (pm-wip-opp is the new branch where we are introducing opp layer. > > I understand that the OPP level of VDD2 may be set by changes to the OPP > level of VDD1 (i.e. resource34xx.c:set_opp) - and modifying VDD1's OPP > via cpufreq seems to be the only way to adjust the VDD2 OPP from > user-land - is this correct? The old /sys/power/vdd2_[opp|lock] was deprecated out. currently the control is for vdd1 OPP using cpufreq and indirect dependency for VDD2, is there a need for direct control of VDD2 freq? -- Regards, Nishanth Menon Ref: [1] http://git.kernel.org/?p=linux/kernel/git/khilman/linux-omap-pm.git;a=bl ob;f=arch/arm/mach-omap2/cpufreq34xx.c;h=07873e87ffc0fef97b4554efc3f17dc 696cb25e3;hb=4f54a09e0ed9b2ee8e1adfe1716297792310d1c6#l46 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
