Subject: Re: [PATCH V2] cpuidle/powernv: Read target_residency value of idle states from DT if available

From: Preeti U Murthy <[email-masked]>
Date: Wed, 28 Jan 2015 15:20:30 +0530

On 01/28/2015 02:45 PM, Stewart Smith wrote:
> Preeti U Murthy <[email-masked]> writes:
>> The device tree now exposes the residency values for different idle states. Read
>> these values instead of calculating residency from the latency values. The values
>> exposed in the DT are validated for optimal power efficiency. However to maintain
>> compatibility with the older firmware code which does not expose residency
>> values, use default values as a fallback mechanism. While at it, handle some
>> cleanups.
> 
> From a "I just merged the patch that exports these values from firmware"
> point of view, using them and falling back looks good.
> 
> (I find the hardcoding of snooze in the driver a bit odd, as is the

Snooze is the only software defined idle state, the rest are platform
specific. The first idle state is usually associated with some sort of a
polling operation and each architecture has a variant to this. This is
why we end up hard-coding this idle state in the driver as far as my
understanding goes.

> hardcoding of max power states to 8 - which could bite us in the future

Hmm.. not sure about this. Need to check.

> if a future processor has more states... but these aren't problems with
> this patch)
> 
> Acked-by: Stewart Smith <[email-masked]>

Thanks!

Regards
Preeti U Murthy