linux-kernel - RE: Re: [PATCH v2 1/3] dt-bindings: imx6q-pcie: add one regulator used to power up pcie phy

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Message-ID: <VI1PR04MB5853E879F65E448244FBEF6F8C629@VI1PR04MB5853.eurprd04.prod.outlook.com>
Date:   Thu, 25 Mar 2021 03:04:58 +0000
From:   Richard Zhu <hongxing.zhu@....com>
To:     Lucas Stach <l.stach@...gutronix.de>,
        "andrew.smirnov@...il.com" <andrew.smirnov@...il.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "kw@...ux.com" <kw@...ux.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "stefan@...er.ch" <stefan@...er.ch>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: RE: Re: [PATCH v2 1/3] dt-bindings: imx6q-pcie: add one regulator
 used to power up pcie phy


> -----Original Message-----
> From: Lucas Stach <l.stach@...gutronix.de>
> Sent: Wednesday, March 24, 2021 5:27 PM
> To: Richard Zhu <hongxing.zhu@....com>; andrew.smirnov@...il.com;
> shawnguo@...nel.org; kw@...ux.com; bhelgaas@...gle.com;
> stefan@...er.ch; lorenzo.pieralisi@....com
> Cc: linux-pci@...r.kernel.org; dl-linux-imx <linux-imx@....com>;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> kernel@...gutronix.de
> Subject: Re: [PATCH v2 1/3] dt-bindings: imx6q-pcie: add one regulator
> used to power up pcie phy
> Hi Richard,
> 
> Am Mittwoch, dem 24.03.2021 um 13:34 +0800 schrieb Richard Zhu:
> > Both 1.8v and 3.3v power supplies can be used by i.MX8MQ PCIe PHY.
> > In default, the PCIE_VPH voltage is suggested to be 1.8v refer to data
> > sheet. When PCIE_VPH is supplied by 3.3v in the HW schematic design,
> > the VREG_BYPASS bits of GPR registers should be cleared from default
> > value 1b'1 to 1b'0. Thus, the internal 3v3 to 1v8 translator would be
> > turned on.
> >
> > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > ---
> >  Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> > b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> > index de4b2baf91e8..3248b7192ced 100644
> > --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> > +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> > @@ -38,6 +38,12 @@ Optional properties:
> >    The regulator will be enabled when initializing the PCIe host and
> >    disabled either as part of the init process or when shutting down the
> >    host.
> > +- vph-supply: Should specify the regulator in charge of PCIe PHY power.
> > +  On i.MX8MQ, both 1.8v and 3.3v power supplies can be used by
> > +i.MX8MQ PCIe
> > +  PHY. In default, the PCIE_VPH voltage is suggested to be 1.8v refer
> > +to data
> > +  sheet. When PCIE_VPH is supplied by 3.3v in the HW schematic
> > +design, the
> > +  VREG_BYPASS bits of GPR registers should be cleared from default
> > +value 1b'1
> > +  to 1b'0.
> 
> This description of the internal driver behavior does not belong into a DT
> binding description.
> Instead the binding should describe the function of the regulator exactly. From
> the datasheet I can see that there are actually 3 supplies (VPH, VP, VPTX)
> going into the PCIe PHY, so "regulator in charge of PCIe PHY power" doesn't
> seem like a very accurate description.
[Richard Zhu] Hi Lucas:  Thanks for your comments.
VP/VPTX are combined together and connected to VDD_PHY_0V9.
Only VPH can be supplied by different voltage power supplies.
So, only VPH is specified in the DT binding, might be used to distinguish different
 HW board designs.

How about this description:
- vph-supply: Should specify the regulator in charge of VPH one of the three
  PCIe PHY powers. This regulator can be supplied by both 1.8v and 3.3v voltage
  supplies. Might be used to distinguish different HW board designs.
> 
> Regards,
> Lucas