linux-kernel - Re: [PATCH v3 02/11] dt-bindings: remoteproc: mediatek: Support MT8195 dual-core SCP

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Date:   Wed, 28 Sep 2022 19:50:33 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     TingHan Shen (沈廷翰) 
        <TingHan.Shen@...iatek.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Tiffany Lin (林慧珊) 
        <tiffany.lin@...iatek.com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        Yunfei Dong (董云飞) 
        <Yunfei.Dong@...iatek.com>,
        "peng.fan@....nxp.com" <peng.fan@....nxp.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "andersson@...nel.org" <andersson@...nel.org>,
        Andrew-CT Chen (陳智迪) 
        <Andrew-CT.Chen@...iatek.com>,
        "mathieu.poirier@...aro.org" <mathieu.poirier@...aro.org>
Cc:     "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 02/11] dt-bindings: remoteproc: mediatek: Support
 MT8195 dual-core SCP

On 28/09/2022 11:17, TingHan Shen (沈廷翰) wrote:
> On Wed, 2022-09-28 at 15:01 +0800, Peng Fan wrote:
>>
>> On 9/27/2022 10:55 AM, Tinghan Shen wrote:
>>> The MT8195 SCP is a dual-core RISC-V MCU. Extend the yaml file
>>> to describe the 2nd core as a subnode of the boot core.
>>>
>>> The configuration register is shared by MT8195 SCP core 0
>>> and core 1. The core 1 can retrieve the information of configuration
>>> registers from parent node.
>>
>> I think the commit message would not convince people you put
>> scp 1 as subnode of scp 0.
>>
>> Regards,
>> Peng.
>>
> Hi Peng,
> 
> Thanks for your review. I should give the most reasonable explanation
> for why SCP 1 is a subnode.
> 
> Adding SCP 1 as a subnode helps to assure finish probing SCP 1
> before starting SCP 0 by using of_platform_populate. It's because
> that I want to probe SCP 1 as a remoteproc subdevice of SCP 0.
> such that when SCP 0 crashed, SCP 0 can reboot SCP 1.

As Peng noted, this is not proper description of hardware. The SCP 0/1
do not have parent-child relationship, so do not model it that way in
Devicetree.

Probe ordering is operating system specific, not related to bindings.

Best regards,
Krzysztof