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

From: Akhil P Oommen
Date: Fri Jun 01 2018 - 07:44:04 EST




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.