Hi, On Fri, Jul 15, 2011 at 02:10:46AM -0600, Paul Walmsley wrote: > > > diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c > > > index e0490bc..e61866c 100644 > > > --- a/arch/arm/mach-omap2/powerdomain.c > > > +++ b/arch/arm/mach-omap2/powerdomain.c > > > @@ -109,6 +109,16 @@ static int _pwrdm_register(struct powerdomain *pwrdm) > > > > > > list_add(&pwrdm->node, &pwrdm_list); > > > > > > + /* > > > + * Program all powerdomain target state as ON; This is to > > > + * prevent domains from hitting low power states (if bootloader > > > + * has target states set to something other than ON) and potentially > > > + * even losing context while PM is not fully initilized. > > > + * The PM late init code can then program the desired target > > > + * state for all the power domains. > > > + */ > > > + pwrdm_set_next_pwrst(pwrdm, PWRDM_POWER_ON); > > > > Just out of curiosity, I was wondering if it really makes sense to power > > up all power domains during boot just to avoid loosing context. Doesn't > > hwmod/omap_device soft-reset all IPs during initialization ? If that's > > really the case, shouldn't we then choose which powerdomains are > > strictly necessary for boot and only power those up ? > > > > Sorry if this is a non-sensical question, but I was curious about it > > ;-) > > This patch only sets the powerdomain's next power state to ON. It doesn't > affect the current power state of the powerdomain. > > Let's say that the bootloader, previous OS (in the kexec case), or ROM > code programs the next power state of some powerdomains to OFF. Let's > also say that the kernel that is booted has PM disabled. The moment a > powerdomain's clockdomains go inactive, the powerdomain will then switch > off and all devices in that powerdomain will lose context. On a > non-PM-enabled kernel, that will be unexpected and will probably cause the > system to crash. This patch prevents that from happening. I see... thanks for clarifying. The comment above the code wasn't really clear about it to me. -- balbi
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