Re: [PATCH 4/6] arm64: Add DTS support for FSL's LS2085A SoC

[Kumar Gala <galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

On Aug 15, 2014, at 10:41 AM, Stuart Yoder <stuart.yoder-KZfg59tc24xl57MIdRCFDg@public.gmane.org> wrote:

> 
> 
>> -----Original Message-----
>> From: Kumar Gala [mailto:galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org]
>> Sent: Friday, August 15, 2014 10:26 AM
>> To: Basu Arnab-B45036
>> Cc: Mark Rutland; Sharma Bhupesh-B45370; arnd-r2nGTMty4D4@public.gmane.org; Catalin Marinas;
>> devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org; Will Deacon; Yoder Stuart-B08248;
>> grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org; linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
>> Subject: Re: [PATCH 4/6] arm64: Add DTS support for FSL's LS2085A SoC
>> 
>> 
>> On Aug 15, 2014, at 10:21 AM, arnab.basu-KZfg59tc24xl57MIdRCFDg@public.gmane.org wrote:
>> 
>>>>> 
>>>>> +	cpus {
>>>>> +		#address-cells = <2>;
>>>>> +		#size-cells = <0>;
>>>>> +
>>>>> +		/* We have 4 clusters having 2 Cortex-A57 cores each */
>>>>> +		cpu@0 {
>>>>> +			device_type = "cpu";
>>>>> +			compatible = "arm,cortex-a57";
>>>>> +			reg = <0x0 0x0>;
>>>>> +			enable-method = "spin-table";
>>>>> +			cpu-release-addr = <0x0 0x8000fff8>;
>>>>> +		};
>>>> 
>>>> I would strongly recommend having a unique cpu-release-addr for each CPU.
>>>> 
>>> 
>>> This is more of a place holder, we intend to patch this address from U-Boot
>>> and use individual release addresses for each CPU.
>> 
>> If you are going to patch it in u-boot, than why not just have u-boot add the
>> property and drop it from here.
>> 
>> If you intend to keep it here, than make <0x0 0x0> and add a comment that says
>> u-boot will fill it out
> 
> As I said to Mark re: the comment on having different release addresses
> per CPU, we are just following existing practice from the existing
> arch/arm64 device trees:
>   apm-storm.dtsi
>   foundation-v8.dts
>   rtsm_ve-aemv8a.dts
> 
> I think one of the reasons the cpu-release-addr is not 0x0 is that 
> UEFI had(?)/has(?) limited ability to do device tree fix ups.  It's
> not a problem at all in u-boot, but there is some reason all
> existing device trees have the same hardcoded address for all
> CPUs.

Are you guys planning on supporting UEFI on this platform?

> So we want to do the standard/conventional thing here that will
> allow are device trees to be used in more than u-boot.

Well, I think the guys would say the standard thing is to move to PSCI.

- k

> 
> Thanks,
> Stuart
> 
> 
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