RE: Problems in cpuidle

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> -----Original Message-----
> From: Kevin Hilman [mailto:khilman@xxxxxxxxxxxxxxxxxxx] 
> Sent: Tuesday, March 10, 2009 8:45 PM
> To: Premi, Sanjeev
> Cc: Högander Jouni; linux-omap@xxxxxxxxxxxxxxx
> Subject: Re: Problems in cpuidle
> 
> "Premi, Sanjeev" <premi@xxxxxx> writes:
> 
> >> -----Original Message-----
> >> From: Högander Jouni [mailto:jouni.hogander@xxxxxxxxx]
> >> Sent: Monday, March 09, 2009 3:36 PM
> >> To: Premi, Sanjeev
> >> Cc: linux-omap@xxxxxxxxxxxxxxx
> >> Subject: Re: Problems in cpuidle
> >> 
> >> "ext Premi, Sanjeev" <premi@xxxxxx> writes:
> >> 
> >> > While working with cpuidle, I have come across these problems.
> >> > I am also working on the solutions, but would be good to 
> hear more 
> >> > thoughts.
> >> >
> >> > 1) The flag 'enable_dyn_sleep' is honoured only in
> >> omap3_idle_bm_check()
> >> >    but in the C1 state, omap3_enter_idle() is invoked directly.
> >> >    So, the system can transition to deeper idle state(s)
> >> >
> >> >    Same is the case with 'sleep_block'.
> >> >
> >> >    Possible Solutions:
> >> >      a)  Call omap3_can_sleep() in omap3_enter_idle().
> >> >          This makes omap3_idle_bm_check() redundant; and
> >> can be removed.
> >> >
> >> >      b)  Make single entry point for all idle states
> >> >          But would be an overkill for C1 state.
> >> >
> >> >      c)  Change omap3_can_sleep() to check for 
> omap_uart_can_sleep()
> >> >          and omap3_fclks_active() only.
> >> >          Move check for 'enable_dyn_sleep' and 'sleep_block' into
> >> >          omap3_enter_idle()
> >> >
> >> >     I believe (c) would be the most optimal.
> >> 
> >> Selecting (c) will break traditional pm_idle. Current plan 
> is to add 
> >> one more C state (C1) which would prevent mpu/core sleep 
> transitions. 
> >> Then remove fclk_active check completely.
> >
> > [sp] I meant doing the same for pm_idle as well.
> >      Also, the new cstate will not help with 'sleep' block.
> >
> >      The proposed change look like:
> >
> > diff --git a/arch/arm/mach-omap2/cpuidle34xx.c 
> > b/arch/arm/mach-omap2/cpuidle34xx index 7fc3cb3..c25158c 100644
> > --- a/arch/arm/mach-omap2/cpuidle34xx.c
> > +++ b/arch/arm/mach-omap2/cpuidle34xx.c
> > @@ -82,6 +82,11 @@ static int omap3_enter_idle(struct 
> cpuidle_device *dev,
> >         /* Used to keep track of the total time in idle */
> >         getnstimeofday(&ts_preidle);
> >
> > +       if (!enable_dyn_sleep)
> > +               goto return_sleep_time;
> > +       if (atomic_read(&sleep_block) > 0)
> > +               goto return_sleep_time;
> > +
> >         /*
> >          * Adjust the idle state (if required).
> >          * Also, ensure that usage statistics of correct 
> state are updated.
> > diff --git a/arch/arm/mach-omap2/pm34xx.c 
> > b/arch/arm/mach-omap2/pm34xx.c index 0716d60..5c7819a 100644
> > --- a/arch/arm/mach-omap2/pm34xx.c
> > +++ b/arch/arm/mach-omap2/pm34xx.c
> > @@ -476,14 +476,10 @@ static int omap3_fclks_active(void)
> >
> >  int omap3_can_sleep(void)
> >  {
> > -       if (!enable_dyn_sleep)
> > -               return 0;
> >         if (!omap_uart_can_sleep())
> >                 return 0;
> >         if (omap3_fclks_active())
> >                 return 0;
> > -       if (atomic_read(&sleep_block) > 0)
> > -               return 0;
> >         return 1;
> >  }
> >
> > @@ -534,6 +530,11 @@ err:
> >
> >  static void omap3_pm_idle(void)
> >  {
> > +       if (!enable_dyn_sleep)
> > +               return;
> > +       if (atomic_read(&sleep_block) > 0)
> > +               return;
> > +
> >         local_irq_disable();
> >         local_fiq_disable();
> >
> 
> Sanjeev,
> 
> I think it's cleaner to just make all the states go through 
> the 'bm_check', so the standard PM idle and CPUidle use the 
> same paths.

[sp] I was trying to avoid duplicate code.
     When all states go thru bm_check, omap3_enter_idle_bm() and
     omap3_enter_idle() can be collapsed into single function.
     Your thoughts?

> Kevin
> 
> --
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