Re: [PATCH] i2c-s3c2410: Add stub runtime power management

[Sylwester Nawrocki <sylvester.nawrocki@gmail.com>]

On 01/22/2012 10:39 PM, Mark Brown wrote:
> On Sun, Jan 22, 2012 at 06:48:36PM +0100, Sylwester Nawrocki wrote:
>> On 01/22/2012 06:27 PM, Bill Gatliff wrote:
> 
>>> I for one would rather see in-kernel drivers that require it, and then
> 
>> In fact we have to deal with the opposite now, as some existing drivers
>> have been used for multiple generations of SoC, where almost unchanged
>> device IPs are deployed. Those drivers were originally written for the
>> simplest SoCs.
> 
> TBH I think most of the devices for which people are running these days
> will be able to get some win from the system wide stuff - the WFI modes
> aren't exactly the latest thing in hardware terms, it's just been a long
> road to getting them supported.  Infrastructure like Mark's PM QoS work
> and Raphael's PM domains work has really helped a lot here.

Indeed, now that I checked some earliest SoC TRMs even the simplest systems
have some sort of intermediate Idle states.

>>> patches in mailing lists that show how to un-require it.  Make it more
>>> painful to avoid PM_RUNTIME, and less painful to use it.
> 
>> Yeah, makes a lot of sense. With new code there is no issue, only the code
>> with long history is sort of troublesome.
> 
> It's mostly a transition management issue I think.  When I repost I'll
> add an additional patch on top which moves the clock gating into the
> runtime PM callbacks, that way the decision on that doesn't block the
> system wide work.

Sounds like a great resolution to the problem, thanks for considering it.
And sorry for disturbing. Let's see what's Kukjin's opinion on that.