linux-kernel - Re: [PATCH v2 2/3] dt-bindings: power: Add mediatek larb definition

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Message-ID: <930b50cb42df3a1a81bb097944c5f18fc5585da3.camel@mediatek.com>
Date: Thu, 28 Mar 2024 07:03:38 +0000
From: Yu-chang Lee (李禹璋) <Yu-chang.Lee@...iatek.com>
To: "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
	MandyJH Liu (劉人僖) <MandyJH.Liu@...iatek.com>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>, "robh@...nel.org"
	<robh@...nel.org>, "krzysztof.kozlowski+dt@...aro.org"
	<krzysztof.kozlowski+dt@...aro.org>, "matthias.bgg@...il.com"
	<matthias.bgg@...il.com>, "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
	"angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>,
	Xiufeng Li (李秀峰) <Xiufeng.Li@...iatek.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, Fan Chen (陳凡)
	<fan.chen@...iatek.com>
Subject: Re: [PATCH v2 2/3] dt-bindings: power: Add mediatek larb definition

On Wed, 2024-03-27 at 12:04 +0100, Krzysztof Kozlowski wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  On 27/03/2024 11:56, Yu-chang Lee (李禹璋) wrote:
> > On Wed, 2024-03-27 at 11:43 +0100, Krzysztof Kozlowski wrote:
> >>   
> >> External email : Please do not click links or open attachments
> until
> >> you have verified the sender or the content.
> >>  On 27/03/2024 11:39, Yu-chang Lee (李禹璋) wrote:
> >>>>>>
> >>>>> Hi,
> >>>>>
> >>>>> I will double check the format of yaml for the next version,
> >> sorry
> >>>> for
> >>>>> inconvenience. But I did test it on mt8188 chromebook, the
> reason
> >>>> why
> >>>>
> >>>> How do you test a binding on chromebook?
> >>>>
> >>>>> power domain need larb node is that when mtcmos power on,
> signal
> >>>> glitch
> >>>>> may produce. Power domain driver must reset larb when this
> happen
> >>>> to 
> >>>>> prevent dummy transaction on bus. That why I need larb node in
> >> dts.
> >>>>
> >>>> No one talks here about larb node...
> >>>
> >>> Sorry, May you elaborate on what information I need to provide to
> >> you
> >>> or it is just a syntax problem I need to fix?
> >>
> >> Please explain the purpose of this property (how is it going to be
> >> used by drivers)and what does it represent.
> >>
> > 
> > It represent SMI LARB(Local ARBitration). In power domain driver
> when
> > power on power domain, It need to reset LARB to prevent potential
> power
> > glitch which may cause dummy transaction on bus. Without taking
> care of
> > this issue it often leads to camera hang in stress test.
> 
> That sounds rather like missing resets... or something else
> connecting
> these devices. Maybe the explanation is just imprecise...
> 

Maybe the term "reset" is misleading here. What power domain driver
trying to do is "set and then clr" the smi larb to clear potential
glitch signal that is already in there. And this step is strongly
related to power domain onf that why I want to add it in to power
domain node without depending larb driver to do the work to prevent
this setting missing.

> Best regards,
> Krzysztof

Best Regards,
yu-chang
>