Subject: [PATCH V3 2/5] ARM: tegra20: cpuidle: add powered-down state for secondary CPU

From: [email-masked] (Stephen Warren)
Date: Thu, 20 Dec 2012 10:43:04 -0700

On 12/17/2012 07:30 PM, Joseph Lo wrote:
> The powered-down state of Tegra20 requires power gating both CPU cores.
> When the secondary CPU requests to enter powered-down state, it saves
> its own contexts and then enters WFI. The Tegra20 had a limition to
> power down both CPU cores. The secondary CPU must waits for CPU0 in
> powered-down state too. If the secondary CPU be woken up before CPU0
> entering powered-down state, then it needs to restore its CPU states
> and waits for next chance.
> 
> Be aware of that, you may see the legacy power state "LP2" in the code
> which is exactly the same meaning of "CPU power down".

> diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c

>  int __init tegra20_cpuidle_init(void)

> +	drv->state_count = sizeof(tegra_idle_states) /
> +			   sizeof(struct cpuidle_state);

Use ARRAY_SIZE() there?

> +	for (i = 0; i < drv->state_count; i++)
> +		memcpy(&drv->states[i], &tegra_idle_states[i],
> +		       sizeof(struct cpuidle_state));

Can't you call memcpy() once:

memcpy(drv->states, tegra_idle_states,
		drv->state_count * sizeof(drv->states[0]));

... although I personally much preferred when all this was just static
initialization directly in tegra_idle_driver, rather than all this messy
copying. Really, struct cpuidle_driver should point at the array, rather
than including it.

> diff --git a/arch/arm/mach-tegra/pm.c b/arch/arm/mach-tegra/pm.c

> @@ -173,6 +173,8 @@ bool __cpuinit tegra_set_cpu_in_lp2(int phy_cpu_id)
>  
>  	if ((phy_cpu_id == 0) && cpumask_equal(cpu_lp2_mask, cpu_online_mask))
>  		last_cpu = true;
> +	else if (phy_cpu_id == 1)
> +		tegra20_cpu_set_resettable_soon();
>  
>  	spin_unlock(&tegra_lp2_lock);
>  	return last_cpu;

Shouldn't the code in that else branch have a run-time check for whether
it's running on Tegra20? When compiled without Tegra20 support,
tegra20_cpu_set_resettable_soon() is a dummy static inline, but when
both Tegra20 and Tegra30 are compiled in, isn't that code going to run
when it shouldn't; pm.c being a common file.

(Peter again, can you please review/ack this series. Thanks)