>-----Original Message----- >From: Paul Walmsley [mailto:paul@xxxxxxxxx] >Sent: Wednesday, July 01, 2009 4:02 AM >To: Nayak, Rajendra >Cc: Kevin Hilman; Kalle Jokiniemi; linux-omap@xxxxxxxxxxxxxxx; >Derrick, David; Woodruff, Richard >Subject: RE: [PATCH 01/04] OMAP3: PM: Disable PER DPLL idle >before OFF, reduces OFF latency by 20ms > >On Tue, 30 Jun 2009, Nayak, Rajendra wrote: > >> >-----Original Message----- >> >From: Kevin Hilman [mailto:khilman@xxxxxxxxxxxxxxxxxxx] >> >Sent: Tuesday, June 30, 2009 12:28 AM >> >To: Nayak, Rajendra >> >Cc: Kalle Jokiniemi; linux-omap@xxxxxxxxxxxxxxx; Derrick, >> >David; Woodruff, Richard >> >Subject: Re: [PATCH 01/04] OMAP3: PM: Disable PER DPLL idle >> >before OFF, reduces OFF latency by 20ms >> > >> >"Nayak, Rajendra" <rnayak@xxxxxx> writes: >> > >> >> >> >> >> >>>-----Original Message----- >> >>>From: Kalle Jokiniemi [mailto:kalle.jokiniemi@xxxxxxxxx] >> >>>Sent: Wednesday, June 17, 2009 6:18 PM >> >>>To: Nayak, Rajendra >> >>>Cc: linux-omap@xxxxxxxxxxxxxxx; Derrick, David; Woodruff, Richard >> >>>Subject: RE: [PATCH 01/04] OMAP3: PM: Disable PER DPLL idle >> >>>before OFF, reduces OFF latency by 20ms >> >>> >> >>>On Wed, 2009-06-17 at 15:38 +0300, Nayak, Rajendra wrote: >> >>>> >> >>>> >-----Original Message----- >> >>>> >From: Kalle Jokiniemi [mailto:kalle.jokiniemi@xxxxxxxxx] >> >>>> >Sent: Wednesday, June 17, 2009 3:56 PM >> >>>> >To: Nayak, Rajendra >> >>>> >Cc: linux-omap@xxxxxxxxxxxxxxx; Derrick, David; >Woodruff, Richard >> >>>> >Subject: RE: [PATCH 01/04] OMAP3: PM: Disable PER DPLL idle >> >>>> >before OFF, reduces OFF latency by 20ms >> >>>> > >> >>>> >On Wed, 2009-06-17 at 12:50 +0300, Nayak, Rajendra wrote: >> >>>> >> >-----Original Message----- >> >>>> >> >From: Kalle Jokiniemi [mailto:kalle.jokiniemi@xxxxxxxxx] >> >>>> >> >Sent: Wednesday, June 17, 2009 1:17 PM >> >>>> >> >To: Nayak, Rajendra >> >>>> >> >Cc: linux-omap@xxxxxxxxxxxxxxx; Derrick, David; >> >Woodruff, Richard >> >>>> >> >Subject: Re: [PATCH 01/04] OMAP3: PM: Disable PER DPLL idle >> >>>> >> >before OFF, reduces OFF latency by 20ms >> >>>> >> > >> >>>> >> >Hi Rajendra, >> >>>> >> > >> >>>> >> >On Tue, 2009-06-16 at 14:52 +0300, Rajendra Nayak wrote: >> >>>> >> >> If autoidle for DPLL4 is enabled in the stored scratchpad >> >>>> >> >> value of CM_AUTOIDLE_PLL then there is an added delay by >> >>>> >> >> the boot ROM when coming out of OFF mode. >> >>>> >> >> The patch disables this bitfield in the stored >> >>>scratchpad value. >> >>>> >> >> >> >>>> >> >> This should significantly reduce CORE OFF latency and also >> >>>> >> >> bring down the threshold for CORE OFF, making OFF >affordable >> >>>> >> >> even with smaller sleep times. >> >>>> >> > >> >>>> >> >I did some measurements on RX-51 with this patch, and it >> >>>> >seems it does >> >>>> >> >not reduce latency, it increases it by few hundred us. >> >>>> >> > >> >>>> >> >Servicing an empty timer interrupt from off mode >> >>>(measured from VDD1 >> >>>> >> >ramp up to start of VDD1 ramp down): >> >>>> >> > >> >>>> >> >with dpll4 patch : ~14100us >> >>>> >> >without patch : ~13600us >> >>>> >> > >> >>>> >> >I attached pictures of both situations. >> >>>> >> > >> >>>> >> >My kernel had only C7 state enabled. >> >>>> >> > >> >>>> >> >Have you measured the latency effects on SDP or some >> >other board? >> >>>> >> >> >>>> >> I haven't done the latency measurements on SDP yet, but >> >>>> >David had done it >> >>>> >> sometime back, using a different codebase though. >> >>>> > >> >>>> >OK, I also used our internal code base. Though the PM >> >>>functionality is >> >>>> >pretty much the same as in l-o:pm branch. >> >>>> > >> >>>> >> >> >>>> >> Can you explain more on how you are measuring the latency >> >>>> >here, I am a bit >> >>>> >> confused. This is supposed to bring down the OFF wakeup >> >>>> >latency, the sleep latency >> >>>> >> remains the same. >> >>>> > >> >>>> >I'm doing a timer interrupt periodically. Servicing that timer >> >>>> >interrupt >> >>>> >takes the same amount of time every time. What varies (with >> >>>the patch) >> >>>> >is the transition times from off to active and back to off. >> >>>> > >> >>>> >In the pictures the top graph shows current and bottom >> >>>graph shows the >> >>>> >VDD1 and VDD2 voltages. I zoomed from the pictures the >> >interval from >> >>>> >when VDD1 goes up, to the point when it starts to go >down again. >> >>>> > >> >>>> >So I measured: wakeup latency + interrupt service + >sleep latency. >> >>>> >> >>>> Is the boot ROM different on the OMAP devices on nokia >h/w or is it >> >>>> the same as that on the SDP? >> >>> >> >>>I have heard that our ROM version would be somehow older >> >version, but I >> >>>really don't have any facts on that matter. >> >> >> >> Oh.. it turns out that when the scratchpad save routine is >> >called, the autoidle >> >> for PER is not even set. Its only set some place later. >> >> So the 20ms or so advantage was always there on l-o pm >> >branch even without this >> >> patch :) >> >> >> > >> >So for the benefit of the archives... >> > >> >I'm dropping this patch since the equivalent is alrady in PM branch. >> >> Kevin, >> >> Today the sequence is such that the PER dpll autoidle is set >only after the first >> scratchpad save (so this patch has no affect). Sometime in >future, if with some change >> in function sequencing we end up enabling the PER dpll >autoidle early on, we might have >> an additional 20ms or so OFF latency without anyone really noticing. >> Would'nt it be good to just have this patch to take care of >any sequencing changes later? > >I don't think we should merge this until David can tell us >more about the >instability that is caused by this patch. Paul, Even without this patch we have always had PER DPLL autoidle disabled in scratchpad in l-o base. This patch does not have any affect today as I said and if there were instabilities to be seen we should have already seen them. regards, Rajendra > > > >- Paul > >-- 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
