linux-kernel - Re: [PATCH v5 3/5] arm64: dts: Add support for Spreadtrum SC9836 SoC in dts and Makefile

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Message-ID: <CA+H2tpFenKzBEvkaHOh7shX7GaYyGFc2CbBTDxgSL9=Wq1Q++g@mail.gmail.com>
Date:	Sat, 17 Jan 2015 16:47:25 +0800
From:	Orson Zhai <orsonzhai@...il.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	marc.zyngier@....com, Chunyan Zhang <chunyan.zhang@...eadtrum.com>,
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	Leo Yan <leo.yan@...aro.org>
Subject: Re: [PATCH v5 3/5] arm64: dts: Add support for Spreadtrum SC9836 SoC
 in dts and Makefile

On Fri, Jan 16, 2015 at 10:09 PM, Mark Rutland <mark.rutland@....com> wrote:
> On Fri, Jan 16, 2015 at 12:49:20PM +0000, Orson Zhai wrote:
>> Hi, Mark,
>>
>> On Fri, Jan 16, 2015 at 6:35 PM, Mark Rutland <mark.rutland@....com> wrote:
>[...]
>>
>>  It returns "status busy" after I type the command below.
>
> Is this while other CPUs are active, or after you've hotplugged out all
> other CPUs? The latter is expected, but the former is not.
>
> Are you able to hotplug CPU0 out and back in while other CPUs are
> active

Yes, I have just tested again and confirm that cpu0 could be
turned on/off when one of the other 3 CPUs was active.

>
> [...]
>
> For this bus you could instead use addresses relative to the bus inside,
> rather than absolute addresses,

Do you mean something like  apb@0 {...} apb@1 {...} ?

> or you could have:
>
> ranges = <0x0 0x70000000 0x0 0x70000000 0x0 0x10000000>;
>
> [...]
>>
>> This initial patch is picked up from a very big dt file.
>> There are several apb buses in this chip.
>
> At the same level us the bus hierarchy?
>
These buses are led by some bus matrix to different areas.
But I'd like treat them simply at same level.
Is it right to do that?

>> So I use apb@...rting-address to separate them.
>> But I remember another rule that the @address needs to equal  first
>> address in property reg array.
>> Do I have to delete @7000000 as well if i delete reg line?
>
> Hmm. I'm not too keen on encoding a reg or unit-address here, because
> the control interface of the bus isn't at that address. If we want to
> add that later then the reg would be different in those cases. Given
> there's no control interface here, there shouldn't be a reg or
> unit-address.
>

Do you mean something like

   ap-ahb { ... };
   aon-ahb { ... };

without using @xxxx ?

   Thanks, Orson

> Just ensure that the name before the unit-address is unique.
>
> Thanks,
> Mark.
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