From mboxrd@z Thu Jan  1 00:00:00 1970
From: t-kristo@ti.com (Tero Kristo)
Date: Fri, 1 Jun 2012 11:06:47 +0300
Subject: [PATCHv3 8/9] ARM: OMAP3: prevent per_clkdm from attempting
 manual domain transitions
In-Reply-To: <4FC8016C.9000801@ti.com>
References: <1338470942-20185-1-git-send-email-t-kristo@ti.com>
 <1338470942-20185-9-git-send-email-t-kristo@ti.com>
 <4FC8016C.9000801@ti.com>
Message-ID: <1338538008.8834.175.camel@sokoban>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Thu, 2012-05-31 at 18:40 -0500, Jon Hunter wrote:
> Hi Tero,
> 
> On 05/31/2012 08:29 AM, Tero Kristo wrote:
> > Previously, PER clock domain was always enabled, as the usecounts
> > for this domain incorrectly always showed positive value. On HW
> > level though, the domain enters idle as it is set in HW supervised
> > mode. Now, when the usecounts reflect real values, PER domain will
> > attempt to enter software supervised idle, which is not supported by the
> > hardware/kernel that well, and causes multiple problems. First of all,
> > coming back from idle, PER domain remains idle as the wakedeps have
> > been disabled for the domain, and this causes a crash with the GPIO
> > code, as the resume code attempts to access domain which is not active.
> > Just enabling the interface clocks for the GPIO does not help, as they
> > are autoidled and don't bring the domain out of idle. Secondly, there
> > are multiple erratas for omap3, which say that the wakedeps should be
> > enabled for the PER domain, see e.g. errata i582 for omap3630.
> > 
> > Signed-off-by: Tero Kristo <t-kristo@ti.com>
> > ---
> >  arch/arm/mach-omap2/clockdomains3xxx_data.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/arm/mach-omap2/clockdomains3xxx_data.c b/arch/arm/mach-omap2/clockdomains3xxx_data.c
> > index 6038adb..0dae4c8 100644
> > --- a/arch/arm/mach-omap2/clockdomains3xxx_data.c
> > +++ b/arch/arm/mach-omap2/clockdomains3xxx_data.c
> > @@ -282,7 +282,7 @@ static struct clockdomain usbhost_clkdm = {
> >  static struct clockdomain per_clkdm = {
> >  	.name		= "per_clkdm",
> >  	.pwrdm		= { .name = "per_pwrdm" },
> > -	.flags		= CLKDM_CAN_HWSUP_SWSUP,
> > +	.flags		= CLKDM_CAN_HWSUP_SWSUP | CLKDM_SKIP_MANUAL_TRANS,
> >  	.dep_bit	= OMAP3430_EN_PER_SHIFT,
> >  	.wkdep_srcs	= per_wkdeps,
> >  	.sleepdep_srcs	= per_sleepdeps,
> 
> So this change is just preventing software from clearing the wakeup-deps
> and keeping the PER clock domain always in HW_AUTO?

Basically yes.

> Sorry for the dumb question, but what is the circumstance under which we
> want to clear the wakeup-deps when we disable the clock domain? I am
> just curious why this is being done in the first place.

Not sure, maybe Paul can answer that question. Personally I don't see
much point in fiddling with the wakedeps.

-Tero