linux-kernel - Re: [PATCH 2/2] dt-bindings: PCI: mediatek-gen3: Add support for controlling power and reset

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Message-ID: <8d954de7f9507099bd9bea6801f446f80bd832aa.camel@mediatek.com>
Date:   Fri, 3 Feb 2023 09:38:37 +0000
From:   Jian Yang (杨戬) <Jian.Yang@...iatek.com>
To:     "krzk@...nel.org" <krzk@...nel.org>,
        "robh@...nel.org" <robh@...nel.org>,
        Jianjun Wang (王建军) 
        <Jianjun.Wang@...iatek.com>, "kw@...ux.com" <kw@...ux.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
        Ryder Lee <Ryder.Lee@...iatek.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Jieyy Yang (杨洁) <Jieyy.Yang@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Chuanjia Liu (柳传嘉) 
        <Chuanjia.Liu@...iatek.com>,
        Qizhong Cheng (程啟忠) 
        <Qizhong.Cheng@...iatek.com>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Rex-BC Chen (陳柏辰) 
        <Rex-BC.Chen@...iatek.com>,
        David-YH Chiu (邱鈺翔) 
        <David-YH.Chiu@...iatek.com>
Subject: Re: [PATCH 2/2] dt-bindings: PCI: mediatek-gen3: Add support for
 controlling power and reset

Dear Krzysztof,

Sorry for the late response and thanks for your comment.

On Wed, 2023-01-11 at 10:30 +0100, Krzysztof Kozlowski wrote:
> On 11/01/2023 04:28, Jian Yang wrote:
> > From: "jian.yang" <jian.yang@...iatek.com>
> > 
> > Add new properties to support control power supplies and reset pin
> > of
> > a downstream component.
> > 
> > Signed-off-by: jian.yang <jian.yang@...iatek.com>
> 
> Please use scripts/get_maintainers.pl to get a list of necessary
> people
> and lists to CC.  It might happen, that command when run on an older
> kernel, gives you outdated entries.  Therefore please be sure you
> base
> your patches on recent Linux kernel.
> 
> > ---
> >  .../bindings/pci/mediatek-pcie-gen3.yaml      | 23
> > +++++++++++++++++++
> >  1 file changed, 23 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/pci/mediatek-pcie-
> > gen3.yaml b/Documentation/devicetree/bindings/pci/mediatek-pcie-
> > gen3.yaml
> > index 7e8c7a2a5f9b..46149cc63989 100644
> > --- a/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml
> > +++ b/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml
> > @@ -84,6 +84,29 @@ properties:
> >      items:
> >        enum: [ phy, mac ]
> >  
> > +  pcie1v8-supply:
> > +    description:
> > +      The regulator phandle that provides 1.8V power to downstream
> > component.
> > +
> > +  pcie3v3-supply:
> > +    description:
> > +      The regulator phandle that provides 3.3V power to downstream
> > component.
> > +
> > +  pcie12v-supply:
> > +    description:
> > +      The regulator phandle that provides 12V power to downstream
> > component.
> > +
> > +  dsc-reset-gpios:
> > +    description:
> > +      The reset GPIO of a downstream component.
> 
> Why you cannot use standard reset-gpios property?

The "dsc-reset-gpios" represents an extra reset pin other than PERST#
required by a PCIe downstream device. But the "reset-gpios", described
in "pci.txt", represents the PERST#. So I tend to add a new property to
meet this requirement.

> 
> > +    maxItems: 1
> > +
> > +  dsc-reset-msleep:
> 
> Wrong property unit/suffix.

Thanks for the correction. I will modify it in v2 patch.

> 
> > +    description:
> > +      The delay time between assertion and de-assertion of a
> > downstream
> > +      component's reset GPIO.
> 
> Why this should be a property of DT?

Same as the reason I described above. I suppose we need to add a
property to let user determine the delay time due to differences
in requirements between various devices.

> 
> > +    maxItems: 1
> 
> maxItems of what?

Seems unnecessary to add a "maxItems" here. Also I will remove it in v2
patch. Thanks a lot.

Best regards,
Jian Yang