linux-kernel - RE: [PATCH 1/1] regulator: fixed: add suspend pm routines for pinctrl

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Date:   Wed, 4 Jan 2017 07:05:23 +0000
From:   Peter Chen <peter.chen@....com>
To:     Mark Brown <broonie@...nel.org>
CC:     "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] regulator: fixed: add suspend pm routines for pinctrl

 
>>On Tue, Jan 03, 2017 at 05:02:47PM +0800, Peter Chen wrote:
>>> At some systems, the pinctrl setting will be lost or needs to set as
>>> "sleep" state to save power consumption. So, we need to configure
>>> pinctrl as "sleep" state when system enters suspend, and as "default"
>>> state after system resumes. In this way, the pinctrl value can be
>>> recovered as "default" state after resuming.
>>
>>I thought this was supposed to be done automatically by the driver core?
>>If not it should be, every single driver is likely to end up with that.
>
>Good idea, I will send a patch for that.
>

After checking more, it is not suitable for driver core do it since different driver
has different usage for "sleep" pinctrl. Below are some examples:

- Some drivers set "idle" for pinctrl when system goes to suspend
- Some drivers has some conditions for setting "sleep" for pinctrl
eg: drivers/net/ethernet/freescale/fec_main.c
- Some drivers may set "sleep" for pinctrl as ->close interface, but not system suspend
interface
- Some drivers can be woken up for "sleep" pinctrl, some may not.

Peter