RE: [PATCH 5/5 v3] OMAP3630: PM: Erratum i583: disable coreoff if < ES1.2

[Vishwanath Sripathy <vishwanath.bs@ti.com>]

Nishant,

> -----Original Message-----
> From: Nishanth Menon [mailto:nm@ti.com]
> Sent: Monday, December 13, 2010 7:13 PM
> To: Vishwanath Sripathy
> Cc: linux-omap; Eduardo Valentin; Kevin Hilman; Tony Lindgren
> Subject: Re: [PATCH 5/5 v3] OMAP3630: PM: Erratum i583: disable
> coreoff if < ES1.2
>
> Vishwanath Sripathy had written, on 12/13/2010 07:35 AM, the
> following:
> > Nishant,
> >
> >> -----Original Message-----
> >> From: linux-omap-owner@vger.kernel.org [mailto:linux-omap-
> >> owner@vger.kernel.org] On Behalf Of Nishanth Menon
> >> Sent: Friday, December 03, 2010 10:34 PM
> >> To: linux-omap
> >> Cc: Eduardo Valentin; Kevin Hilman; Tony Lindgren; Nishanth Menon
> >> Subject: [PATCH 5/5 v3] OMAP3630: PM: Erratum i583: disable
> coreoff if
> >> < ES1.2
> >>
> >> From: Eduardo Valentin <eduardo.valentin@nokia.com>
> >>
> >> Limitation i583: Self_Refresh Exit issue after OFF mode
> >>
> >> Issue:
> >> When device is waking up from OFF mode, then SDRC state machine
> >> sends
> >> inappropriate sequence violating JEDEC standards.
> >>
> >> Impact:
> >> OMAP3630 < ES1.2 is impacted as follows depending on the
> platform:
> >> CS0: for 38.4MHz as internal sysclk, DDR content seen to be stable,
> >> while
> >> 	for all other sysclk frequencies, varied levels of instability
> >> 	seen based on varied parameters.
> >> CS1: impacted
> >>
> >> This patch takes option #3 as recommended by the Silicon erratum:
> >> Avoid core power domain transitioning to OFF mode. Power
> consumption
> >> impact is expected in this case.
> >> To do this, we route OFF requests to RET request on the impacted
> >> revisions
> >> of silicon.
> >>
> >> Cc: Kevin Hilman <khilman@deeprootsystems.com>
> >> Cc: Tony Lindgren <tony@atomide.com>
> >>
> >> [nm@ti.com: rebased the code to 2.6.37-rc2- short circuit code
> changed
> >> a bit]
> >> Signed-off-by: Nishanth Menon <nm@ti.com>
> >> Signed-off-by: Eduardo Valentin <eduardo.valentin@nokia.com>
> >> ---
> >> v3: no functional change in erratum wa implementation, just
> registration
> >> of
> >>  	erratum is collated to a single cpu detection and version check
> >> v2: https://patchwork.kernel.org/patch/365262/
> >>     rebased to this patch series instead of depending on hs changes
> >>     fix typo for macro definition
> >> v1: http://marc.info/?l=linux-omap&m=129013173425266&w=2
> >>  arch/arm/mach-omap2/pm34xx.c |   14 ++++++++++++++
> >>  1 files changed, 14 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/arch/arm/mach-omap2/pm34xx.c b/arch/arm/mach-
> >> omap2/pm34xx.c
> >> index b49e02b..ba3c0d6 100644
> >> --- a/arch/arm/mach-omap2/pm34xx.c
> >> +++ b/arch/arm/mach-omap2/pm34xx.c
> >> @@ -56,6 +56,7 @@
> >>  #define OMAP343X_CONTROL_REG_VALUE_OFFSET  0xc8
> >>
> >>  #define RTA_ERRATUM_i608		(1 << 0)
> >> +#define SDRC_WAKEUP_ERRATUM_i583	(1 << 1)
> >>  static u16 pm34xx_errata;
> >>  #define IS_PM34XX_ERRATUM(id)		(pm34xx_errata & (id))
> >>
> >> @@ -406,6 +407,17 @@ void omap_sram_idle(void)
> >>  	}
> >>
> >>  	/* CORE */
> >> +	/*
> >> +	 * Erratum i583: implementation for ES rev < Es1.2 on 3630
> >> +	 * We cannot enable OFF mode in a stable form for previous
> >> +	 * revisions, transition instead to RET
> >> +	 */
> >> +	if (IS_PM34XX_ERRATUM(SDRC_WAKEUP_ERRATUM_i583) &&
> >> +			(core_next_state == PWRDM_POWER_OFF)) {
> >> +		pwrdm_set_next_pwrst(core_pwrdm,
> >> PWRDM_POWER_RET);
> >> +		core_next_state = PWRDM_POWER_RET;
> >> +	}
> >
> > Since next_state in pwrst_list (for core) is not updated, this is
throwing
> > up an error "Powerdomain (core_pwrdm) didn't enter target state 0"
> when
> > you off mode is enabled for ES1.1 or lesser (in suspend path). It's
not
> > really true that Core has not entered target state. It has entered
> > Retention state which is the actual target state set in
omap_sram_idle.
> > However it did not enter the state that was passed by
> omap3_pm_suspend. Is
> > this expected behavior?
>
> we could go both ways on this - this patch will(as you noticed) indicate
> that the transition failed on <ES1.2, or we could make it entirely
> transparent(by modifying the the pwrst_list - claim we achieved off,
> while not really hitting off - I personally dont think that is correct.
The point I am making is that you cannot distinguish between genuine off
/retention failure since this message is thrown for both pass and fail.
May be an additional trace message indicating that system entered
retention instead of off (for ES<1.2) will be useful.

Vishwa
>
> --
> Regards,
> Nishanth Menon