linux-kernel - Re: [linux-sunxi] Re: [PATCH 2/7] dt-bindings: add binding for the Allwinner A64 DE2 bus

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Date:   Thu, 22 Mar 2018 14:08:43 +0800
From:   Icenowy Zheng <icenowy@...c.io>
To:     jernej.skrabec@...l.net,
        Jernej Škrabec <jernej.skrabec@...l.net>,
        linux-sunxi@...glegroups.com
CC:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [linux-sunxi] Re: [PATCH 2/7] dt-bindings: add binding for the Allwinner A64 DE2 bus



于 2018年3月22日 GMT+08:00 上午1:13:42, "Jernej Škrabec" <jernej.skrabec@...l.net> 写到:
>Hi all,
>
>Dne sreda, 21. marec 2018 ob 03:18:13 CET je Icenowy Zheng napisal(a):
>> 于 2018年3月21日 GMT+08:00 上午2:46:46, Maxime Ripard
><maxime.ripard@...tlin.com> 
>写到:
>> >On Sat, Mar 17, 2018 at 01:53:49AM +0800, Icenowy Zheng wrote:
>> >> All the sub-blocks of Allwinner A64 DE2 needs the SRAM C on A64
>SoC
>> >
>> >to
>> >
>> >> be claimed, otherwise the whole DE2 space is inaccessible.
>> >> 
>> >> Add a device tree binding of the DE2 part as a sub-bus.
>> >
>> >Where did you get the info that it was a bus?
>> 
>> There's no direct evidence, just some guess.
>> 
>> The DE2 is a whole part that is just allocated a memory
>> space at the user manual, and the SRAM controls the
>> access to all modules in the DE2.
>> 
>> So it might be a bus.
>> 
>> Implement it as a bus is a clear representation on A64.
>
>Since there is already syscon for same mmio region, we migh as well use
>it 
>when loading ccu-sun8i-de2 driver on A64.
>
>Other options, like SRAM driver or bus driver, might better represent
>HW, but 

I think the device tree should properly represent the HW,
it's a basic requirment.

>then we would have two DT nodes covering same mmio region, which I
>think is 
>not really acceptable.

It's acceptable, and DE2 is not the only user of SRAM controller so far.

VE will also need a SRAM region to be claimed.

>
>Any suggestions?
>
>BTW, H6 has same design in this regard.
>
>Best regards,
>Jernej