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

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

Best Regards
Richard Zhu

-----Original Message-----
From: Bjorn Helgaas <helgaas@kernel.org>
Sent: Friday, May 7, 2021 5:09 AM
To: Richard Zhu <hongxing.zhu@nxp.com>
Cc: l.stach@pengutronix.de; andrew.smirnov@gmail.com;
shawnguo@kernel.org; kw@linux.com; bhelgaas@google.com;
stefan@agner.ch; lorenzo.pieralisi@arm.com; linux-pci@vger.kernel.org;
dl-linux-imx [off-list ref]; linux-arm-kernel@lists.infradead.org;
linux-kernel@vger.kernel.org; kernel@pengutronix.de
Subject: [EXT] Re: [RESEND v4 2/2] PCI: imx: clear vreg bypass when pcie vph
voltage is 3v3

Caution: EXT Email

On Tue, Mar 30, 2021 at 04:08:21PM +0800, Richard Zhu wrote:

quoted

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

quoted

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.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

quoted

@@ -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)

quoted

                                 imx6_pcie_grp_offset(imx6_pcie),

IMX8MQ_GPR_PCIE_REF_USE_PAD,

quoted

IMX8MQ_GPR_PCIE_REF_USE_PAD);

quoted

+             /*
+              * 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),

quoted

+

IMX8MQ_GPR_PCIE_VREG_BYPASS,

quoted

+                                        0);
              break;
      case IMX7D:
              regmap_update_bits(imx6_pcie->iomuxc_gpr,

IOMUXC_GPR12,

quoted

@@ -1130,6 +1143,13 @@ static int imx6_pcie_probe(struct

platform_device *pdev)

quoted

              imx6_pcie->vpcie = NULL;
      }

+     imx6_pcie->vph = devm_regulator_get_optional(&pdev->dev,

"vph");

quoted

+     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

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