>-----Original Message----- >From: Kalle Jokiniemi [mailto:[email protected]] >Sent: Wednesday, June 17, 2009 1:17 PM >To: Nayak, Rajendra >Cc: [email protected]; 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. 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. > >- Kalle > > >> This patch however does not optimize the C state threshold for >> CORE OFF states based on the new latency. >> >> Signed-off-by: Rajendra Nayak <[email protected]> >> --- >> arch/arm/mach-omap2/control.c | 7 +++++++ >> 1 files changed, 7 insertions(+), 0 deletions(-) >> >> diff --git a/arch/arm/mach-omap2/control.c >b/arch/arm/mach-omap2/control.c >> index c9407c0..a7159a9 100644 >> --- a/arch/arm/mach-omap2/control.c >> +++ b/arch/arm/mach-omap2/control.c >> @@ -238,6 +238,13 @@ void omap3_save_scratchpad_contents(void) >> cm_read_mod_reg(PLL_MOD, CM_CLKEN); >> prcm_block_contents.cm_autoidle_pll = >> cm_read_mod_reg(PLL_MOD, >OMAP3430_CM_AUTOIDLE_PLL); >> + /* >> + * ROM restore takes 20mS longer if PER idle is enabled >before OFF. >> + * Clear feature before sleep. The origional idle state is >> + * restored by software as part of wake procedure. >> + */ >> + prcm_block_contents.cm_autoidle_pll &= >~OMAP3430_AUTO_PERIPH_DPLL_MASK; >> + >> prcm_block_contents.cm_clksel1_pll = >> cm_read_mod_reg(PLL_MOD, >OMAP3430_CM_CLKSEL1_PLL); >> prcm_block_contents.cm_clksel2_pll = >-- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
