linux-kernel - Re: [PATCH 1/2] dt-bindings: phy: mediatek: tphy: add a property for force-mode switch

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Message-ID: <b351bdfeb1e782bd559f3c33da916de6a24b3446.camel@mediatek.com>
Date:   Thu, 30 Nov 2023 02:28:14 +0000
From:   Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>
To:     "vkoul@...nel.org" <vkoul@...nel.org>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
        Macpaul Lin (林智斌) 
        <Macpaul.Lin@...iatek.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
CC:     Pablo Sun (孫毓翔) <pablo.sun@...iatek.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Bear Wang (萩原惟德) 
        <bear.wang@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH 1/2] dt-bindings: phy: mediatek: tphy: add a property for
 force-mode switch

On Mon, 2023-11-27 at 15:09 +0800, Macpaul Lin wrote:
> On 11/25/23 18:37, Krzysztof Kozlowski and Chunfeng Yun wrote:
> > 	
> > 
> > External email : Please do not click links or open attachments
> > until you 
> > have verified the sender or the content.
> > 
> > On 25/11/2023 02:23, Chunfeng Yun wrote:
> > > Due to some old SoCs with shared t-phy only support force-mode
> > > switch, and
> > > can't use compatible to distinguish between shared and non-shared 
> > > t-phy,
> > > add a property to supported it.
> > > But now prefer to use "mediatek,syscon-type" on new SoC as far as
> > > possible.
> > > 
> > > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > > ---
> > >  Documentation/devicetree/bindings/phy/mediatek,tphy.yaml | 6
> > > ++++++
> > >  1 file changed, 6 insertions(+)
> > > 
> > > diff --git
> > > a/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
> > > b/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
> > > index 2bb91542e984..eedba5b7025e 100644
> > > --- a/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
> > > +++ b/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
> > > @@ -235,6 +235,12 @@ patternProperties:
> > >            Specify the flag to enable BC1.2 if support it
> > >          type: boolean
> > >  
> > > +      mediatek,force-mode:
> > > +        description:
> > > +          Use force mode to switch shared phy mode, perfer to
> > > use the bellow
> > 
> > I still do not understand what is the "force mode" you want to use.
> > What
> > modes do you have? What are the characteristics of force mode?
> > 
> > Also, please run spellcheck.
> > 
> > Best regards,
> > Krzysztof
> > 
> 
> Thanks!
> 
> 1. I've tested this patch and it could solve the clock unstable for
> XHCI1 on mt8195 or mt8395 during system boot up or during
> unload/reload the phy driver.
> 
> The error message has been listed as follows.
> 
> [   13.849936][   T72] xhci-mtk 11290000.usb: supply vbus not found, 
> using dummy regulator
> [   13.851300][   T72] xhci-mtk 11290000.usb: uwk - reg:0x400,
> version:104
> [   13.852624][   T72] xhci-mtk 11290000.usb: xHCI Host Controller
> [   13.853393][   T72] xhci-mtk 11290000.usb: new USB bus
> registered, 
> assigned bus number 3
> [   13.874490][   T72] xhci-mtk 11290000.usb: clocks are not stable
> (0x3d0f)
> [   13.875369][   T72] xhci-mtk 11290000.usb: can't setup: -110
> [   13.876091][   T72] xhci-mtk 11290000.usb: USB bus 3 deregistered
> [   13.877081][   T72] xhci-mtk: probe of 11290000.usb failed with
> error 
> -110
> 
> 2. This is a fix patch to XHCI1 since MT8195 has been upstream.
> Please add "Fixes:" tags and "Cc: stable@...nel.org" to back ward
> porting to previous stable trees.
> 
> For example, add
> Fixes: 6b5ef194611e5 ("phy: mediatek: tphy: remove macros to prepare 
> bitfield")
> is suggested since the force-mode was missing in the previous
> implementation which causes hardware function was abnormal.
> However, add
> Fixes: 33d18746fa514 ("phy: phy-mtk-tphy: use new io helpers to
> access 
> register")
> will be better since the USB support for mt8195 is already enabled
> in 
> late 2021.
It don't take into account this case, it assume that only use the
default mode (PCIe).

> 
> 3. How about we revise the description as follows for more precisely?
> 
> mediatek,force-mode:
>    description:
>      The force mode is used to manually switch the shared PHY mode
>      between USB and PCIe. When force-mode is set, the USB 3.0 mode
>      will be selected. 
seems not right, the mode/type is selected by the phy consumer.

> This is typically required for older SoCs
>      that do not automatically manage PHY mode switching.
>      For newer SoCs that support it, it is preferable to use the
>      "mediatek,syscon-type" property instead.
>    type: boolean

> 
> Thanks,
> Macpaul Lin