linux-kernel - Re: [PATCH] acpi/cpuidle: reinitialize power_usage values when adding/removing C-states

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Date:	Mon, 22 Oct 2012 19:21:18 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Julius Werner <jwerner@...omium.org>
CC:	linux-kernel@...r.kernel.org, len.brown@...el.com, khilman@...com,
	rjw@...k.pl, deepthi@...ux.vnet.ibm.com, akpm@...ux-foundation.org,
	Trinabh Gupta <g.trinabh@...il.com>, snanda@...omium.org,
	Lists Linaro-dev <linaro-dev@...ts.linaro.org>
Subject: Re: [PATCH] acpi/cpuidle: reinitialize power_usage values when adding/removing
 C-states

On 10/22/2012 07:13 PM, Julius Werner wrote:
>> Could we just say this is always true because state[i+1] consumes less
>> than state[i] ?
>>
>> And then just remove the 'set_power_state' function, and the field
>> 'driver->power_specified' ?
>>
>> That will cleanup the code and fix this problem, no ?
> 
> I totally agree with your analysis. Even if a driver were to set
> proper usage values (and the power_specified bit), none of the
> existing governors would care about those actual numbers (and since
> the vast majority of drivers uses fake values anyway, this is not
> likely to change in the future). This seems to be a classic example of
> unnecessary over-engineering.
> 
> I am mostly interested in getting that bug fixed right now, but
> removing unnecessary code is always a good thing. If you think it
> would have a good chance of getting merged, I would be happy to draft
> up a larger patch that refactors power_usage away completely.

I am in favor of removing the unnecessary code as it fixes a bug also
but I am not a maintainer, so I can't tell if it has a good chance to be
merged as a bug fix.

I think Rafael can tell us what approach he would prefer.

Thanks
  -- Daniel


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