[U-Boot] ARM: PSCI 0.1 vs 0.2

[Jan Kiszka]

On 2014-11-10 14:29, bhupesh.sharma at freescale.com wrote:
> Hi, 
> 
>> -----Original Message-----
>> From: u-boot-bounces at lists.denx.de [mailto:u-boot-bounces at lists.denx.de]
>> On Behalf Of Jan Kiszka
>> Sent: Monday, November 10, 2014 6:56 PM
>> To: Marc Zyngier
>> Cc: u-boot at lists.denx.de
>> Subject: Re: [U-Boot] ARM: PSCI 0.1 vs 0.2
>>
>> On 2014-11-10 14:08, Marc Zyngier wrote:
>>> On 10/11/14 12:51, Jan Kiszka wrote:
>>>> Hi Marc,
>>>>
>>>> what is the motivation to expose a PSCI 0.1 interface in U-boot,
>>>> instead of 0.2? Support for preexisting users of 0.1? The kernel
>>>> seems to be happy with both, and I'm now wondering if we should
>>>> actually add the legacy version to Jailhouse as well (I hope we can
>> avoid this).
>>>
>>> The initial rational was simple: at the time this code was written,
>>> the
>>> 0.2 spec still in review, and nobody was implementing it. Supporting
>>> 0.1 was the only viable use-case.
>>>
>>>> Still studying the logic: Is it possible to provide both interfaces,
>>>> and would it make sense?
>>>
>>> Supporting both is very easy. Just output the 0.2 function numbers
>>> that actually make sense for 0.1 and have both compatible strings.
>>
>> Ah, cool - parameters and return values of, say, CPU_ON/OFF are
>> compatible across both versions?
>>
>> Jan
>>
>> --
> 
> We did send out some ARMv8 PSCI v0.2 u-boot patches, which can be seen here:
> 
> http://permalink.gmane.org/gmane.comp.boot-loaders.u-boot/194210

Nice. I guess that could be reused for ARMv7 as well, at least
conceptually. You are using C for some PSCI functions, specifically for
cache flushing? Need to dig deeper...

Jan

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