linux-kernel - RE: Re: [RESEND v4 2/2] PCI: imx: clear vreg bypass when pcie vph voltage is 3v3

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Message-ID: <VI1PR04MB5853B8F4928D85D1490C05A48C579@VI1PR04MB5853.eurprd04.prod.outlook.com>
Date:   Fri, 7 May 2021 06:18:08 +0000
From:   Richard Zhu <hongxing.zhu@....com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     "l.stach@...gutronix.de" <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>,
        "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: [RESEND v4 2/2] PCI: imx: clear vreg bypass when pcie vph
 voltage is 3v3


> -----Original Message-----
> Subject: [EXT] Re: [RESEND v4 2/2] PCI: imx: clear vreg bypass when pcie vph
> voltage is 3v3
> On Tue, Mar 30, 2021 at 04:08:21PM +0800, Richard Zhu wrote:
> > 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.
> 
> Maybe something like this?
> 
>   PCI: imx6: Enable PHY internal regulator when supplied >3V
> 
>   The i.MX8MQ PCIe PHY needs 1.8V but can by supplied by either a 1.8V
>   or a 3.3V regulator.
> 
>   The "vph-supply" DT property tells us which external regulator
>   supplies the PHY.  If that regulator supplies anything over 3V,
>   enable the PHY's internal 3.3V-to-1.8V regulator.
> 
[Richard Zhu] Hi Bjorn:
Thanks for your comments.
vph is the "high-voltage power supply" of the PHY.
How do you think with the following one with some minor updates?

   PCI: imx6: Enable PHY internal regulator when supplied >3V

   The i.MX8MQ PCIe PHY needs 1.8V in default but can be supplied by
   either a 1.8V or a 3.3V regulator.

   The "vph-supply" DT property tells us which external regulator
   supplies the PHY. If that regulator supplies anything over 3V,
   enable the PHY's internal 3.3V-to-1.8V regulator.
BR
Richard
> > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > Reviewed-by: Lucas Stach <l.stach@...gutronix.de>
> > ---
> >  drivers/pci/controller/dwc/pci-imx6.c | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > b/drivers/pci/controller/dwc/pci-imx6.c
> > index 853ea8e82952..94b43b4ecca1 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -37,6 +37,7 @@
> >  #define IMX8MQ_GPR_PCIE_REF_USE_PAD          BIT(9)
> >  #define IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE_EN  BIT(10)
> >  #define IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE     BIT(11)
> > +#define IMX8MQ_GPR_PCIE_VREG_BYPASS          BIT(12)
> >  #define IMX8MQ_GPR12_PCIE2_CTRL_DEVICE_TYPE  GENMASK(11, 8)
> >  #define IMX8MQ_PCIE2_BASE_ADDR
> 0x33c00000
> >
> > @@ -80,6 +81,7 @@ struct imx6_pcie {
> >       u32                     tx_swing_full;
> >       u32                     tx_swing_low;
> >       struct regulator        *vpcie;
> > +     struct regulator        *vph;
> >       void __iomem            *phy_base;
> >
> >       /* power domain for pcie */
> > @@ -621,6 +623,17 @@ static void imx6_pcie_init_phy(struct imx6_pcie
> *imx6_pcie)
> >                                  imx6_pcie_grp_offset(imx6_pcie),
> >
> IMX8MQ_GPR_PCIE_REF_USE_PAD,
> >
> IMX8MQ_GPR_PCIE_REF_USE_PAD);
> > +             /*
> > +              * Regarding the datasheet, the PCIE_VPH is suggested
> > +              * to be 1.8V. If the PCIE_VPH is supplied by 3.3V, the
> > +              * VREG_BYPASS should be cleared to zero.
> > +              */
> > +             if (imx6_pcie->vph &&
> > +                 regulator_get_voltage(imx6_pcie->vph) > 3000000)
> > +                     regmap_update_bits(imx6_pcie->iomuxc_gpr,
> > +
> imx6_pcie_grp_offset(imx6_pcie),
> > +
> IMX8MQ_GPR_PCIE_VREG_BYPASS,
> > +                                        0);
> >               break;
> >       case IMX7D:
> >               regmap_update_bits(imx6_pcie->iomuxc_gpr,
> IOMUXC_GPR12,
> > @@ -1130,6 +1143,13 @@ static int imx6_pcie_probe(struct
> platform_device *pdev)
> >               imx6_pcie->vpcie = NULL;
> >       }
> >
> > +     imx6_pcie->vph = devm_regulator_get_optional(&pdev->dev,
> "vph");
> > +     if (IS_ERR(imx6_pcie->vph)) {
> > +             if (PTR_ERR(imx6_pcie->vph) != -ENODEV)
> > +                     return PTR_ERR(imx6_pcie->vph);
> > +             imx6_pcie->vph = NULL;
> > +     }
> > +
> >       platform_set_drvdata(pdev, imx6_pcie);
> >
> >       ret = imx6_pcie_attach_pd(dev);
> > --
> > 2.17.1
> >