linux-kernel - Re: [PATCH v2 0/3] add support for power off check in suspend

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Message-ID: <5f0cf9d1-9a6a-4c97-8f56-6c5ae8af1564@microchip.com>
Date:   Mon, 28 Jan 2019 09:50:23 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <Ludovic.Desroches@...rochip.com>, <linux@...linux.org.uk>,
        <lgirdwood@...il.com>, <broonie@...nel.org>, <rjw@...ysocki.net>,
        <pavel@....cz>, <len.brown@...el.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2 0/3] add support for power off check in suspend

Hi Pavel, Rafael,

Do you have some other hints I could follow in order to solve the
scenario I tried to cover with these patches, if these are not
a proper fit for the current code?

Thank you,
Claudiu Beznea

On 08.01.2019 12:56, Claudiu Beznea - M18063 wrote:
> From: Claudiu Beznea <claudiu.beznea@...rochip.com>
> 
> Hi,
> 
> AT91 platforms support a power saving mode where SoC's power is cut off (we call
> it backup mode). The resume is done with the help of bootloaders. To be able to
> suspend/resume Linux to/from this mode all the drivers suspend/resume callbacks
> should save/restore the content of all the active registers. We have 2 problems
> we are trying to solve:
> - some of these drivers are shared with other non Microchip SoCs (e.g. macb
>   driver) and we don't want to disturbe other users of corresponding IPs with
>   all the register save/restore operations;
> - the suspend/resume time for the rest of the power saving mode we are using
>   could be improved if we would know in drivers the suspend mode the platform
>   is switched to.
> 
> A solution that would have been solve our problems was proposed in [1] but in
> the end it wasn't accepted. It ended up with the introduction of
> pm_suspend_target_state variable that could be used along with the changes in
> this series.
> 
> While the discussion of [1] progressed it has been proposed (in [2]) to
> implement a function that would tell if the platform's power would be cut off
> at the end of the suspend procedure.
> 
> The patches in this series does as follows:
> 1/3 - add a new member to platform_suspend_ops that will tell if platform's
>       power will be cut off at the end of the suspend procedure; drivers could
>       use it via platform_off_in_suspend()
> 2/3 - add a new function to regulator's core that could be used to check if a
>       proper regulator has been configured (via DT) to be powered off in
>       suspend. This is used on this series to check the CPU's regulator is
>       properly configured in DT to be turned off in suspend.
> 3/3 - fill .off_in_suspend member of at91_pm_ops; the functionality in patch 2/3
>       is used to double check CPU's regulator would be turned off in suspend.
> 
> Thank you,
> Claudiu Beznea
> 
> [1] https://lkml.org/lkml/2017/6/22/938
> [2] https://lkml.org/lkml/2017/7/16/457
> 
> Changes in v2:
> - remove !! instruction in regulator_is_disabled_in_suspend() and
>   at91_pm_state_allowed()
> - s/weather/wether in patch 1/1
> 
> Claudiu Beznea (3):
>   PM / Suspend: Add support to check if platform's power is off in
>     suspend
>   regulator: core: add helper to check if regulator is disabled in
>     suspend
>   ARM: at91: pm: add support for .off_in_suspend
> 
>  arch/arm/mach-at91/pm.c            | 61 +++++++++++++++++++++++++++++++++++---
>  drivers/regulator/core.c           | 17 +++++++++++
>  include/linux/regulator/consumer.h |  7 +++++
>  include/linux/suspend.h            |  6 ++++
>  kernel/power/suspend.c             | 13 ++++++++
>  5 files changed, 100 insertions(+), 4 deletions(-)
>