Subject: [PATCH 03/10] OMAP3: PM: move device-specific special cases from PM core into CPUidle

From: [email-masked] (Kevin Hilman)
Date: Tue, 21 Sep 2010 10:00:02 -0700

Paul Walmsley <[email-masked]> writes:

> Hi Kevin,
>
> On Wed, 15 Sep 2010, Kevin Hilman wrote:
>
>> In an effort to simplify the core idle path, move any device-specific
>> special case handling from the core PM idle path into the CPUidle
>> pre-idle checking path.
>> 
>> This keeps the core, interrupts-disabled idle path streamlined and
>> independent of any device-specific handling, and also allows CPUidle
>> to do the checking only for certain C-states as needed.  This patch
>> has the device checks in place for all states with the CHECK_BM flag,
>> namely all states >= C2.
>> 
>> This patch was inspired by a similar patch written by Tero Kristo as
>> part of a larger series to add INACTIVE state support.
>
> As with the original patch, I don't quite understand the improvement 
> here.  In particular, this part:
>
>> diff --git a/arch/arm/mach-omap2/cpuidle34xx.c b/arch/arm/mach-omap2/cpuidle34xx.c
>> index 3d3d035..0923b82 100644
>> --- a/arch/arm/mach-omap2/cpuidle34xx.c
>> +++ b/arch/arm/mach-omap2/cpuidle34xx.c
>> @@ -233,14 +234,54 @@ static int omap3_enter_idle_bm(struct cpuidle_device *dev,
>>  			       struct cpuidle_state *state)
>>  {
>>  	struct cpuidle_state *new_state = next_valid_state(dev, state);
>> +	u32 core_next_state, per_next_state = 0, per_saved_state = 0;
>> +	u32 cam_state;
>> +	struct omap3_processor_cx *cx;
>> +	int ret;
>>  
>>  	if ((state->flags & CPUIDLE_FLAG_CHECK_BM) && omap3_idle_bm_check()) {
>>  		BUG_ON(!dev->safe_state);
>>  		new_state = dev->safe_state;
>> +		goto select_state;
>> +	}
>> +
>> +	cx = cpuidle_get_statedata(state);
>> +	core_next_state = cx->core_state;
>> +
>> +	/*
>> +	 * Prevent idle completely if CAM is active.
>> +	 * CAM does not have wakeup capability in OMAP3.
>> +	 */
>> +	cam_state = pwrdm_read_pwrst(cam_pd);
>> +	if (cam_state == PWRDM_POWER_ON) {
>> +		new_state = dev->safe_state;
>> +		goto select_state;
>>  	}
>>  
>> +	/*
>> +	 * Prevent PER off if CORE is not in retention or off as this
>> +	 * would disable PER wakeups completely.
>> +	 */
>> +	per_next_state = per_saved_state = pwrdm_read_next_pwrst(per_pd);
>> +	if ((per_next_state == PWRDM_POWER_OFF) &&
>> +	    (core_next_state > PWRDM_POWER_RET)) {
>> +		per_next_state = PWRDM_POWER_RET;
>> +		pwrdm_set_next_pwrst(per_pd, per_next_state);
>> +	}
>> +
>> +	/* Are we changing PER target state? */
>> +	if (per_next_state != per_saved_state)
>> +		pwrdm_set_next_pwrst(per_pd, per_next_state);
>
> In this case, the PER / CORE constraints don't have anything to do with 
> the MPU or CPUIdle, so they don't seem to belong in the CPUIdle code.  The 
> extra comments are certainly nice -- they make it more clear as to what is 
> going on here -- but maybe those can just be added to pm34xx.c ?

CPUidle currently manages MPU and CORE powerdomains, so the CORE
constraints seem to make perfect sense here (at least to me.)

The question is probably more about the PER constraints.

The basic goal of this is to streamline the core idle (omap_sram_idle())
to be the minimum streamline idle, and to move all the constraint
checking and activity checking to higher layers (like CPUidle.)
Specifically, I'm working towards moving the device-specific idle
constraints out of the core idle path (omap_sram_idle()) and move them
into higher layers where we're checking for activity etc.

This is just a baby step towards moving the device-idle out of CPUidle
completely to a place where it can be managed by the driver themeselves
using runtime PM or by using constraints instead of these hard-coded
hacks.

Kevin

>> +
>> +select_state:
>>  	dev->last_state = new_state;
>> -	return omap3_enter_idle(dev, new_state);
>> +	ret = omap3_enter_idle(dev, new_state);
>> +
>> +	/* Restore original PER state if it was modified */
>> +	if (per_next_state != per_saved_state)
>> +		pwrdm_set_next_pwrst(per_pd, per_saved_state);
>> +
>> +	return ret;
>>  }
>>  
>>  DEFINE_PER_CPU(struct cpuidle_device, omap3_idle_dev);
>> @@ -328,7 +369,8 @@ void omap_init_power_states(void)
>>  			cpuidle_params_table[OMAP3_STATE_C2].threshold;
>>  	omap3_power_states[OMAP3_STATE_C2].mpu_state = PWRDM_POWER_ON;
>>  	omap3_power_states[OMAP3_STATE_C2].core_state = PWRDM_POWER_ON;
>> -	omap3_power_states[OMAP3_STATE_C2].flags = CPUIDLE_FLAG_TIME_VALID;
>> +	omap3_power_states[OMAP3_STATE_C2].flags = CPUIDLE_FLAG_TIME_VALID |
>> +				CPUIDLE_FLAG_CHECK_BM;
>>  
>>  	/* C3 . MPU CSWR + Core inactive */
>>  	omap3_power_states[OMAP3_STATE_C3].valid =
>> @@ -426,6 +468,8 @@ int __init omap3_idle_init(void)
>>  
>>  	mpu_pd = pwrdm_lookup("mpu_pwrdm");
>>  	core_pd = pwrdm_lookup("core_pwrdm");
>> +	per_pd = pwrdm_lookup("per_pwrdm");
>> +	cam_pd = pwrdm_lookup("cam_pwrdm");
>>  
>>  	omap_init_power_states();
>>  	cpuidle_register_driver(&omap3_idle_driver);
>> diff --git a/arch/arm/mach-omap2/pm34xx.c b/arch/arm/mach-omap2/pm34xx.c
>> index 429268e..bb2ba1e 100644
>> --- a/arch/arm/mach-omap2/pm34xx.c
>> +++ b/arch/arm/mach-omap2/pm34xx.c
>> @@ -346,7 +346,6 @@ void omap_sram_idle(void)
>>  	int core_next_state = PWRDM_POWER_ON;
>>  	int core_prev_state, per_prev_state;
>>  	u32 sdrc_pwr = 0;
>> -	int per_state_modified = 0;
>>  
>>  	if (!_omap_sram_idle)
>>  		return;
>> @@ -391,19 +390,10 @@ void omap_sram_idle(void)
>>  	if (per_next_state < PWRDM_POWER_ON) {
>>  		omap_uart_prepare_idle(2);
>>  		omap2_gpio_prepare_for_idle(per_next_state);
>> -		if (per_next_state == PWRDM_POWER_OFF) {
>> -			if (core_next_state == PWRDM_POWER_ON) {
>> -				per_next_state = PWRDM_POWER_RET;
>> -				pwrdm_set_next_pwrst(per_pwrdm, per_next_state);
>> -				per_state_modified = 1;
>> -			} else
>> +		if (per_next_state == PWRDM_POWER_OFF)
>>  				omap3_per_save_context();
>> -		}
>>  	}
>>  
>> -	if (pwrdm_read_pwrst(cam_pwrdm) == PWRDM_POWER_ON)
>> -		omap2_clkdm_deny_idle(mpu_pwrdm->pwrdm_clkdms[0]);
>> -
>>  	/* CORE */
>>  	if (core_next_state < PWRDM_POWER_ON) {
>>  		omap_uart_prepare_idle(0);
>> @@ -470,8 +460,6 @@ void omap_sram_idle(void)
>>  		if (per_prev_state == PWRDM_POWER_OFF)
>>  			omap3_per_restore_context();
>>  		omap_uart_resume_idle(2);
>> -		if (per_state_modified)
>> -			pwrdm_set_next_pwrst(per_pwrdm, PWRDM_POWER_OFF);
>>  	}
>>  
>>  	/* Disable IO-PAD and IO-CHAIN wakeup */
>> -- 
>> 1.7.2.1
>> 
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>
>
> - Paul