Re: [PATCH 6/8] OMAP: PM CONSTRAINTS: implement the devices wake-up latency constraints

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Kevin,

On Fri, Sep 16, 2011 at 1:47 AM, Kevin Hilman <khilman@xxxxxx> wrote:
> Jean Pihet <jean.pihet@xxxxxxxxxxxxxx> writes:
>
>> Implement the devices wake-up latency constraints using the global
>> device PM QoS notification handler which applies the constraints to the
>> underlying layer by calling the corresponding function at hwmod level.
>>
>> Note: the bus throughput function is implemented but currently is
>> a no-op. A new PM QoS class for the bus throughput needs to be
>> added.
>>
>> Tested on OMAP3 Beagleboard and OMAP4 Pandaboard in RET/OFF using wake-up
>> latency constraints on MPU, CORE and PER.
>>
>> Signed-off-by: Jean Pihet <j-pihet@xxxxxx>
>
> This patch does 2 things.
>
> 1) removes the MPU lat stuff from the OMAP PM layer (since it's now
>   available in a generic form
> 2) implements device wake-up latency constraints
>
> This should be broken up into two parts.
>
> Also, this patch seems to remove a bunch of stuff that was just added in
> patch 2/8.  Probably best to create the new OMAP PM layer after remving
> the unused stuff.
>
> It think the code using the new per-device PM QoS API should also live
> outside the OMAP PM layer, since it's not related, and we want to get
> rid of the OMAP PM layer eventually.
>
> Speaking of which..., the more I think about it, the more I think we
> should take this opportunity to clean and/or remove the OMAP PM layer
> completely.


I agree completely, the OMAP PM 'plugin' layer is useless and anyway
an empty implementation for now.

> With your work, other than the no-op bus throughput API, it's basically
> unused.  I think that rather than creating a new OMAP PM layer just to
> have a a no-op bus throughput function here, I think it's time
> to remove OMAP PM completely.
Ok. The only useful code is to register a PM QoS notifier in order to
apply the constraints to the power domains.
Are you suggesting to move this code to e.g. pmxxx.c?

>   This might also give some incentive
> for a PM QoS bus throughput constraint as well.
Sure the tput constraints should be implemented as well.

>
> Of course, Paul can make the final decision there whether to remove it
> now, but I think it's time.
>
> Just to prove it's usefulness (or lack thereof), Here's a hack that
> combined with your patch 1/8 shows that it is pretty easy to remove.
>
> Kevin

Thanks!
Jean
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