RE: Problems in cpuidle

["Premi, Sanjeev" <premi@ti.com>]

> -----Original Message-----
> From: Högander Jouni [mailto:jouni.hogander@nokia.com] 
> Sent: Monday, March 09, 2009 3:36 PM
> To: Premi, Sanjeev
> Cc: linux-omap@vger.kernel.org
> Subject: Re: Problems in cpuidle
> 
> "ext Premi, Sanjeev" <premi@ti.com> 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();

> 
> --
> Jouni Högander
> 
> --
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