linux-kernel - Re: [PATCH 3/8] ARM64: dts: Prepare configs for Amlogic Meson GXBaby

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Message-ID: <56D5C119.8070609@arm.com>
Date:	Tue, 1 Mar 2016 16:19:37 +0000
From:	Sudeep Holla <sudeep.holla@....com>
To:	Andreas Färber <afaerber@...e.de>,
	linux-meson@...glegroups.com
Cc:	Sudeep Holla <sudeep.holla@....com>,
	Carlo Caione <carlo@...one.org>,
	linux-arm-kernel@...ts.infradead.org,
	Matthias Brugger <mbrugger@...e.com>,
	Nicolas Saenz <nicolassaenzj@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	devicetree <devicetree@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/8] ARM64: dts: Prepare configs for Amlogic Meson GXBaby



On 01/03/16 15:18, Andreas Färber wrote:
> Am 01.03.2016 um 15:43 schrieb Sudeep Holla:
>> On 29/02/16 23:44, Andreas Färber wrote:
>>> +    psci {
>>> +        compatible = "arm,psci";
>>
>> Any particular reason why PSCI v0.2 or above is not supported on this
>> platform. PSCI v0.1 is very old now and I assume this platform is
>> relatively new.
>
> I am not affiliated with Amlogic or Tronsmart, so I cannot answer why.
>

OK

>>> +        method = "smc";
>>> +        cpu_suspend = <0xc4000001>;
>>> +        cpu_off = <0x84000002>;
>>> +        cpu_on = <0xc4000003>;
>>> +        migrate = <0xc4000005>;
>>
>> Atleast the functions ids look like v0.2 or above. So check if it's
>> actually v0.2 or above
>
> If you let me know how! Just change the compatible string to -0.2 and
> wait for some big boom or watch out for any misbehavior in particular?

Not exactly. Just having -0.2 in compatible will issue PSCI_VERSION
which *should be* available in v0.2 and above. If you get error there,
then we can *assume* it's PSCI v0.1. Hopefully it be sanely return
error if that's not implemented.

Note that we can only assume, as it might be v0.2 but missed to
implement PSCI_VERSION which is mandatory though.

> Are there any memory locations to check the version or something visible
> in U-Boot source code indicating it?
>

Ah so, PSCI is implemented in U-Boot on this platform ? If so, and if
the source is available it should not be that hard to figure that out.

-- 
Regards,
Sudeep