Re: cpuidle omap 4430, some clarifications please?

2011-01-10 Thread Etienne Le Sueur 



On 10/01/11 6:41 PM, Santosh Shilimkar wrote:

-Original Message-
From: linux-omap-ow...@vger.kernel.org [mailto:linux-omap-
ow...@vger.kernel.org] On Behalf Of Etienne Le Sueur
Sent: Monday, January 10, 2011 10:36 AM
To: linux-omap@vger.kernel.org
Subject: cpuidle omap 4430, some clarifications please?

Hello,

I'm using linux-2.6.35.3 on a pandaboard taking power measurements
in different idle states (I've written a userspace governor for
cpuidle).

It seems like the code which is supposed to put the cores in deep
sleep never actually gets called, see code below with my comments...

Taken from arch/arm/mach-omap2/cpuidle44xx.c, omap4_enter_idle,
which gets called by cpuidle:

===

  /*
   * Do only WFI for non-boot CPU(aux cores)
   */
  if (dev-cpu) {
  wmb();
  do_wfi();
  goto return_sleep_time;
  }

So on OMAP 4430, CPU1 never goes deeper than WFI?

  /*
   * Do only a WFI as long as CPU1 is online
   */
  if (num_online_cpus()  1) {
  wmb();
  do_wfi();
  goto return_sleep_time;
  }

So while CPU1 is online (it never goes offline due to the above
code) CPU0 will never go deeper than WFI?

  /*
   * Hold on till CPU1 hits OFF
   */
  cpu1_state = pwrdm_read_pwrst(cpu1_pd);
  if (cpu1_state != PWRDM_POWER_OFF) {
  wmb();
  do_wfi();
  goto return_sleep_time;
  }

It seems like CPU1 will never 'hit off' ?

  if (cx-type  OMAP4_STATE_C1)
  clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER,
cpu_id);

#ifdef CONFIG_PM_DEBUG
  pwrdm_pre_transition();
#endif

The code below never gets called, therefore neither CPU0, CPU1 nor
the MPU go into a deeper sleep state?

  pwrdm_set_logic_retst(mpu_pd, cx-mpu_logic_state);
  omap4_set_pwrdm_state(mpu_pd, cx-mpu_state);

  omap4_set_pwrdm_state(core_pd, cx-core_state);

  omap4_enter_sleep(dev-cpu, cx-cpu0_state);

=

Can someone clarify for me?


Yes.
Simple rule is, no low power states are targeted when both CPUs
are online. The C-states gets targeted only when secondary
CPU gets offline through hotplug infrastrcutre. CPU1 hits
OFF mode through hot-plug path and not via idle.

With this CPU1 hits OFF state, and IDLE thread running
on master CPU can hit deeper low power states. It's more of
hardware restriction what is there on OMAP4.

Can you elaborate on the hardware restrictions? It seems strange to me that there would be this sort of limitation on an SoC that is designed 
for low-power.

To put it in slightly simpler terms,

In SMP mode, no active PM is exercised in IDLE and
gets triggered when secondary cores are out of the system.

Hope this clarifies.

Regards,
Santosh

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cpuidle omap 4430, some clarifications please?

2011-01-09 Thread Etienne Le Sueur 

Hello,

I'm using linux-2.6.35.3 on a pandaboard taking power measurements in different 
idle states (I've written a userspace governor for cpuidle).

It seems like the code which is supposed to put the cores in deep sleep never 
actually gets called, see code below with my comments...

Taken from arch/arm/mach-omap2/cpuidle44xx.c, omap4_enter_idle, which gets 
called by cpuidle:

===

/*
 * Do only WFI for non-boot CPU(aux cores)
 */
if (dev-cpu) {
wmb();
do_wfi();
goto return_sleep_time;
}

So on OMAP 4430, CPU1 never goes deeper than WFI?

/*
 * Do only a WFI as long as CPU1 is online
 */
if (num_online_cpus()  1) {
wmb();
do_wfi();
goto return_sleep_time;
}

So while CPU1 is online (it never goes offline due to the above code) CPU0 will 
never go deeper than WFI?

/*
 * Hold on till CPU1 hits OFF
 */
cpu1_state = pwrdm_read_pwrst(cpu1_pd);
if (cpu1_state != PWRDM_POWER_OFF) {
wmb();
do_wfi();
goto return_sleep_time;
}

It seems like CPU1 will never 'hit off' ?

if (cx-type  OMAP4_STATE_C1)
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, cpu_id);

#ifdef CONFIG_PM_DEBUG
pwrdm_pre_transition();
#endif

The code below never gets called, therefore neither CPU0, CPU1 nor the MPU go 
into a deeper sleep state?

pwrdm_set_logic_retst(mpu_pd, cx-mpu_logic_state);
omap4_set_pwrdm_state(mpu_pd, cx-mpu_state);

omap4_set_pwrdm_state(core_pd, cx-core_state);

omap4_enter_sleep(dev-cpu, cx-cpu0_state);

=

Can someone clarify for me?

Cheers,
Etienne Le Sueur
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RE: cpuidle omap 4430, some clarifications please?

2011-01-09 Thread Santosh Shilimkar 
 -Original Message-
 From: linux-omap-ow...@vger.kernel.org [mailto:linux-omap-
 ow...@vger.kernel.org] On Behalf Of Etienne Le Sueur
 Sent: Monday, January 10, 2011 10:36 AM
 To: linux-omap@vger.kernel.org
 Subject: cpuidle omap 4430, some clarifications please?

 Hello,

 I'm using linux-2.6.35.3 on a pandaboard taking power measurements
 in different idle states (I've written a userspace governor for
 cpuidle).

 It seems like the code which is supposed to put the cores in deep
 sleep never actually gets called, see code below with my comments...

 Taken from arch/arm/mach-omap2/cpuidle44xx.c, omap4_enter_idle,
 which gets called by cpuidle:

 ===

  /*
   * Do only WFI for non-boot CPU(aux cores)
   */
  if (dev-cpu) {
  wmb();
  do_wfi();
  goto return_sleep_time;
  }

 So on OMAP 4430, CPU1 never goes deeper than WFI?

  /*
   * Do only a WFI as long as CPU1 is online
   */
  if (num_online_cpus()  1) {
  wmb();
  do_wfi();
  goto return_sleep_time;
  }

 So while CPU1 is online (it never goes offline due to the above
 code) CPU0 will never go deeper than WFI?

  /*
   * Hold on till CPU1 hits OFF
   */
  cpu1_state = pwrdm_read_pwrst(cpu1_pd);
  if (cpu1_state != PWRDM_POWER_OFF) {
  wmb();
  do_wfi();
  goto return_sleep_time;
  }

 It seems like CPU1 will never 'hit off' ?

  if (cx-type  OMAP4_STATE_C1)
  clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER,
 cpu_id);

 #ifdef CONFIG_PM_DEBUG
  pwrdm_pre_transition();
 #endif

 The code below never gets called, therefore neither CPU0, CPU1 nor
 the MPU go into a deeper sleep state?

  pwrdm_set_logic_retst(mpu_pd, cx-mpu_logic_state);
  omap4_set_pwrdm_state(mpu_pd, cx-mpu_state);

  omap4_set_pwrdm_state(core_pd, cx-core_state);

  omap4_enter_sleep(dev-cpu, cx-cpu0_state);

 =

 Can someone clarify for me?

Yes.
Simple rule is, no low power states are targeted when both CPUs
are online. The C-states gets targeted only when secondary
CPU gets offline through hotplug infrastrcutre. CPU1 hits
OFF mode through hot-plug path and not via idle.

With this CPU1 hits OFF state, and IDLE thread running
on master CPU can hit deeper low power states. It's more of
hardware restriction what is there on OMAP4.

To put it in slightly simpler terms,

In SMP mode, no active PM is exercised in IDLE and
gets triggered when secondary cores are out of the system.

Hope this clarifies.

Regards,
Santosh
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