linux-kernel - Re: [PATCHv4 7/7] ARM: dts: Add device tree sources for Exynos3250

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Date:	Fri, 09 May 2014 10:01:39 +0200
From:	Tomasz Figa <t.figa@...sung.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>,
	Tomasz Figa <tomasz.figa@...il.com>
Cc:	kgene.kim@...sung.com, linux-kernel@...r.kernel.org,
	linux@....linux.org.uk, ben-linux@...ff.org, arnd@...db.de,
	olof@...om.net, marc.zyngier@....com, thomas.abraham@...aro.org,
	kyungmin.park@...sung.com, inki.dae@...sung.com,
	sw0312.kim@...sung.com, hyunhee.kim@...sung.com,
	yj44.cho@...sung.com, chanho61.park@...sung.com,
	sajjan.linux@...il.com, tushar.behera@...aro.org,
	sachin.kamat@...aro.org, linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.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>
Subject: Re: [PATCHv4 7/7] ARM: dts: Add device tree sources for Exynos3250



On 09.05.2014 09:10, Chanwoo Choi wrote:
> Hi Tomasz,
> 
> On 05/09/2014 02:02 PM, Tomasz Figa wrote:
>> Hi Chanwoo,
>>
>> On 09.05.2014 03:06, Chanwoo Choi wrote:
>>> On 04/26/2014 09:51 AM, Tomasz Figa wrote:
>>>> On 25.04.2014 03:16, Chanwoo Choi wrote:
>>
>> [snip]
>>
>>>>> +    cpus {
>>>>> +        #address-cells = <1>;
>>>>> +        #size-cells = <0>;
>>>>> +
>>>>> +        cpu@0 {
>>>>> +            device_type = "cpu";
>>>>> +            compatible = "arm,cortex-a7";
>>>>> +            reg = <0>;
>>>>> +            clock-frequency = <1000000000>;
>>>>> +        };
>>>>
>>>> Why only one CPU? I believe Exynos3250 is dual core.
>>>
>>> I'll add cpu1 information.
>>>
>>>> Also are physical IDs of the cores really 0 and 1? On Exynos4210 for example they are 0x900 and 0x901, while on Exynos4212 they are 0xa00 and 0xa01. Please check this.
>>>
>>> The 'reg' property means only hardware id(hwid) of CPU.
>>> You can check it on arm_dt_init_cpu_maps() in arch/arm/kernel/devtree.c.h.
>>> or Documentation/devicetree/bindings/arm/cpus.txt.
>>>
>>
>> Well, as described in Documentation/devicetree/bindings/arm/cpus.txt, on 32-bit ARM v7 or later CPUs the "reg" property should be equal to the lower 24-bits of MPIDR value of given CPU, which in addition to core ID includes also cluster ID, which can be non-zero, even on single cluster SoCs (like it is on Exynos4210 and 4x12).
> 
> I checked the lower 24-bit of MPIDR value for Exynos3250 in arm_dt_init_cpu_maps().
> - the lower 24-bit of MPIDR for CPU0 is '0x0'.

Fair enough. Thanks.

Best regards,
Tomasz
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