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SubjectRe: [PATCH 02/14] dt-bindings: soc: milbeaut: Add Milbeaut trampoline description
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Hi,

On 2018/11/30 17:16, Stephen Boyd wrote:
> Quoting Sugaya, Taichi (2018-11-29 04:24:51)
>> On 2018/11/28 11:01, Stephen Boyd wrote:
>>> Quoting Sugaya Taichi (2018-11-18 17:01:07)
>>>> create mode 100644 Documentation/devicetree/bindings/soc/socionext/socionext,m10v.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/soc/socionext/socionext,m10v.txt b/Documentation/devicetree/bindings/soc/socionext/socionext,m10v.txt
>>>> new file mode 100644
>>>> index 0000000..f5d906c
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/soc/socionext/socionext,m10v.txt
>>>> @@ -0,0 +1,12 @@
>>>> +Socionext M10V SMP trampoline driver binding
>>>> +
>>>> +This is a driver to wait for sub-cores while boot process.
>>>> +
>>>> +- compatible: should be "socionext,smp-trampoline"
>>>> +- reg: should be <0x4C000100 0x100>
>>>> +
>>>> +EXAMPLE
>>>> + trampoline: trampoline@0x4C000100 {
>>> Drop the 0x part of unit addresses.
>>
>> Okay.
>>
>>
>>>> + compatible = "socionext,smp-trampoline";
>>>> + reg = <0x4C000100 0x100>;
>>> Looks like a software construct, which we wouldn't want to put into DT
>>> this way. DT doesn't describe drivers.
>> We would like to use this node only getting the address of the
>> trampoline area
>> in which sub-cores wait.  (They have finished to go to this area in previous
>> bootloader process.)
>
> Is this area part of memory, or a special SRAM? If it's part of memory,
> I would expect this node to be under the reserved-memory node and
> pointed to by some other node that uses this region. Could even be the
> CPU nodes.

Yes, 0x4C000100 is a part of memory under the reserved-memory node. So
we would like to use the SRAM ( allocated 0x00000000 ) area instead.
BTW, sorry, the trampoline address of this example is simply wrong. We
were going to use a part of the SRAM from the beginning.

>
>>
>> So should we embed the constant value in source codes instead of getting
>> from
>> DT because the address is constant at the moment? Or is there other
>> approach?
>>
>
> If it's constant then that also works. Why does it need to come from DT
> at all then?

We think it is not good to embed constant value in driver codes and do
not have another way...
Are there better ways?

Thanks
Sugaya Taichi

>

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