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

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Date:   Mon, 10 May 2021 01:15:41 +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

Hi:
It seems that the email sent on May07, is missing.
Re-send it.

Best Regards
Richard Zhu

> -----Original Message-----
> From: Richard Zhu
> Sent: Friday, May 7, 2021 2:18 PM
...
> Subject: RE: Re: [RESEND v4 2/2] PCI: imx: clear vreg bypass when pcie vph
> voltage is 3v3
> 
> 
> > -----Original Message-----
> > Subject: 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
> > >