Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power

From: Sudeep Holla <sudeep.holla@arm.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Lina Iyer <lina.iyer@linaro.org>,
	John Stultz <john.stultz@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
	Rob Herring <robh+dt@kernel.org>,
	Magnus Damm <magnus.damm@gmail.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Linux PM list <linux-pm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power
Date: Tue, 21 Feb 2017 16:49:20 +0000	[thread overview]
Message-ID: <937ce0a4-96d0-2379-486b-fd8a305cb716@arm.com> (raw)
In-Reply-To: <CAMuHMdWXEw+rkzd2_7fetmwsaSZqXBD_YHsMV2XnLBxAn0Eh8A@mail.gmail.com>

Hi Geert,

On 21/02/17 16:36, Geert Uytterhoeven wrote:
> Hi Sudeep,
> 
> On Tue, Feb 21, 2017 at 11:50 AM, Sudeep Holla <sudeep.holla@arm.com> wrote:
>> 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@glider.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
> 
> This is useful to support other wake-up sources. Linux has a standardized
> way to handle wake-up sources, which may be circumvented by calling PSCI
> SYSTEM_SUSPEND.
> 
>> suggested please try using freeze_ops.
> 
> Freezing the system works, but requires manual configurarion.
> This should be done automatically.
> 

What sort of manual configuration ? I am just asking to understand you
setup better.

>> 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.
> 
> This should be used automatically if the system can't wake-up from
> suspend-to-RAM using the configured wake-up sources.
> 

Yes.

-- 
Regards,
Sudeep