linux-kernel - Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if SYSTEM

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Message-ID: <bed72738-93c7-c0da-d6c7-383d6881dbdd@arm.com>
Date:   Tue, 21 Feb 2017 10:50:03 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        Lina Iyer <lina.iyer@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Rob Herring <robh+dt@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Magnus Damm <magnus.damm@...il.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if
 SYSTEM_SUSPEND cuts power



On 20/02/17 20:33, Geert Uytterhoeven wrote:
> Nothing in the PSCI specification requires the SoC to remain powered and
> to support wake-up sources when suspended using SYSTEM_SUSPEND.
> If the firmware implements the PSCI SYSTEM_SUSPEND operation by cutting
> power to the SoC, the only possibly wake-up sources are thus the ones
> connected to the PMIC.
> 
> Document and add support for an "arm,psci-system-suspend-is-power-down"
> DT property, so Linux uses a different suspend method when other wake-up
> sources (e.g. wake on LAN, UART or GPIO) are enabled.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
>  Documentation/devicetree/bindings/arm/psci.txt | 11 +++++++++++
>  drivers/firmware/psci.c                        | 13 ++++++++++---
>  2 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/arm/psci.txt b/Documentation/devicetree/bindings/arm/psci.txt
> index a2c4f1d524929bb7..16e390ecb7531028 100644
> --- a/Documentation/devicetree/bindings/arm/psci.txt
> +++ b/Documentation/devicetree/bindings/arm/psci.txt
> @@ -68,6 +68,17 @@ state nodes, as per bindings in [1]) must specify the following properties:
>  		Definition: power_state parameter to pass to the PSCI
>  			    suspend call.
>  
> + - arm,psci-system-suspend-is-power-down
> +		Nothing in the PSCI specification requires the SoC to remain
> +		powered and to support wake-up sources when suspended using
> +		SYSTEM_SUSPEND.

Again, yes SoC can be powered down but you give no reasons why this is
useful other than help you to hack around to implement suspend_ops. As
suggested please try using freeze_ops.

After commit a94e502c22b6 ("cpuidle: dt: assign ->enter_freeze to same
as ->enter callback function"), you can enter suspend-to-idle(a.k.a
freeze state) on all platforms using ARM DT cpuidle driver.

-- 
Regards,
Sudeep