Re: [RFC] PM / devfreq: Add support for alerts

[Akhil P Oommen]

On 5/31/2018 11:47 AM, MyungJoo Ham wrote:
> > Currently, DEVFREQ reevaluates the device state periodically and/or
> > based on the OPP list changes. Private API has to be exposed to allow
> > the device driver to alert/notify the governor to reevaluate when a new
> > set of data is available. This makes the governor more coupled to a
> > particular device driver. We can improve here by exposing a DEVFREQ API
> > to allow the device drivers to send generic alerts to the governor.
> >
> > Signed-off-by: Akhil P Oommen <akhilpo@xxxxxxxxxxxxxx>
> > ---
> >   drivers/devfreq/devfreq.c  | 21 +++++++++++++++++++++
> >   drivers/devfreq/governor.h |  1 +
> >   include/linux/devfreq.h    |  5 +++++
> >   3 files changed, 27 insertions(+)
> Hello Akhil,
>
> It appears that this will have the same effect with
> "[PATCH 08/11] PM / devfreq: Make update_devfreq() public" from Matthias Kaehlcke, doesn't it?
>
>
> Cheers,
> MyungJoo
Hi MyngJoo,

The patch you mentioned is a step in the right direction. But this patch 
allows:
1. the governor to decide whether to reevaluate or not. I feel it would 
be a better architecture (better Separation of Concern) if that decision 
is left to the governor alone.
2. the devices to share multiple types of alerts. A governor may use 
these alerts for internal bookkeeping/algorithm and decide to reevaluate 
policy when it is necessary. Since we are opening up a new devfreq API 
for devices, isn't it better to go for a generic one?

Regards,
Akhil.