[PATCH v2 1/3] ARM: imx: Add imx cpuidle driver

[Russell King - ARM Linux]

On Fri, Sep 16, 2011 at 12:27:48PM -0500, Robert Lee wrote:
> Introduce a new cpuidle driver which provides the common cpuidle
> functionality necessary for any imx soc cpuidle implementation.

I think its probably about time we said no to this duplication of CPU
idle infrastructure.  There seems to be a common pattern appearing
through all SoCs - they're all doing this:

> +static int imx_enter_idle(struct cpuidle_device *dev,
> +			       struct cpuidle_state *state)
> +{
> +	struct timeval before, after;
> +	int idle_time;
> +
> +	local_irq_disable();
> +	local_fiq_disable();
> +
> +	do_gettimeofday(&before);
> +
> +	mach_cpuidle(dev, state);
> +
> +	do_gettimeofday(&after);
> +
> +	local_fiq_enable();
> +	local_irq_enable();
> +
> +	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
> +		(after.tv_usec - before.tv_usec);
> +
> +	return idle_time;
> +}

in some form, where 'do_gettimeofday' might be ktime_get() or
getnstimeofday().  If we can standardize on which of the many time
functions can be used (which would be a definite plus) we should move
this out to common code.

Maybe also the initialization code could be standardized and improved
too - for instance, what if you boot with maxcpus=1 on a platform
supporting 2 CPUs, and you bring CPU1 online from userspace?  When
these CPU idle initialization functions are called, only one CPU will
be online, and as they use 'for_each_cpu(cpu_id, cpu_online_mask)'
CPU1 will be missing the cpu idle init.