Re: [PATCH v2] PCI: imx: Add imx6sx suspend/resume support

[Andrey Smirnov <andrew.smirnov@gmail.com>]

On Wed, Nov 7, 2018 at 5:57 AM Leonard Crestez <leonard.crestez@nxp.com> wrote:
>
> Enable PCI suspend/resume support on imx6sx socs. This is similar to
> imx7d with a few differences:
>
> * The PM_Turn_Off bit is exposed through an IOMUX GPR, like all other
> pcie control bits on 6sx.
> * The pcie_inbound_axi clk needs to be turned off in suspend. On resume
> it is restored via resume -> deassert_core_reset -> enable_ref_clk.
>
> Most of the resume logic is shared with the initial reset after probe.
>
> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
>
> ---
> Changes since v1:
> * Use a switch statement in imx6_pcie_pm_turnoff. The DT-based turnoff
> path is still an if statement.
> * Did not split imx6_pcie_clk_disable or call it from other paths, this
> would bring complications and is somewhat unrelated.
> * See v1 comments: https://lore.kernel.org/patchwork/patch/996806/
>
>  drivers/pci/controller/dwc/pci-imx6.c       | 44 ++++++++++++++++++---
>  include/linux/mfd/syscon/imx6q-iomuxc-gpr.h |  1 +
>  2 files changed, 40 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 2cbef2d7c207..54625569d0bc 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -771,41 +771,75 @@ static void imx6_pcie_ltssm_disable(struct device *dev)
>         }
>  }
>
>  static void imx6_pcie_pm_turnoff(struct imx6_pcie *imx6_pcie)
>  {
> -       reset_control_assert(imx6_pcie->turnoff_reset);
> -       reset_control_deassert(imx6_pcie->turnoff_reset);
> +       struct device *dev = imx6_pcie->pci->dev;
> +
> +       /* Some variants have a turnoff reset in DT */
> +       if (imx6_pcie->turnoff_reset) {
> +               reset_control_assert(imx6_pcie->turnoff_reset);
> +               reset_control_deassert(imx6_pcie->turnoff_reset);
> +               goto pm_turnoff_sleep;
> +       }
> +
> +       /* Others poke directly at IOMUXC registers */
> +       switch (imx6_pcie->variant) {
> +       case IMX6SX:
> +               regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
> +                               IMX6SX_GPR12_PCIE_PM_TURN_OFF,
> +                               IMX6SX_GPR12_PCIE_PM_TURN_OFF);
> +               regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
> +                               IMX6SX_GPR12_PCIE_PM_TURN_OFF, 0);
> +               break;
> +       default:
> +               dev_err(dev, "PME_Turn_Off not implemented\n");
> +               return;

Purely optionally, if you feel like avoiding goto you can change this to:

default:
    if (!imx6_pcie->turnoff_reset) {
        dev_err(dev, "PME_Turn_Off not implemented\n");
        return;
    }

    reset_control_assert(imx6_pcie->turnoff_reset);
    reset_control_deassert(imx6_pcie->turnoff_reset);
    break;

but that's up to you. FWIW, patch looks reasonable:

Reviewed-by: Andrey Smirnov <andrew.smirnov@gmail.com>

> +       }
>
>         /*
>          * Components with an upstream port must respond to
>          * PME_Turn_Off with PME_TO_Ack but we can't check.
>          *
>          * The standard recommends a 1-10ms timeout after which to
>          * proceed anyway as if acks were received.
>          */
> +pm_turnoff_sleep:
>         usleep_range(1000, 10000);
>  }
>
>  static void imx6_pcie_clk_disable(struct imx6_pcie *imx6_pcie)
>  {
>         clk_disable_unprepare(imx6_pcie->pcie);
>         clk_disable_unprepare(imx6_pcie->pcie_phy);
>         clk_disable_unprepare(imx6_pcie->pcie_bus);
>
> -       if (imx6_pcie->variant == IMX7D) {
> +       switch (imx6_pcie->variant) {
> +       case IMX6SX:
> +               clk_disable_unprepare(imx6_pcie->pcie_inbound_axi);
> +               break;
> +       case IMX7D:
>                 regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
>                                    IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
>                                    IMX7D_GPR12_PCIE_PHY_REFCLK_SEL);
> +               break;
> +       default:
> +               break;
>         }
>  }
>
> +static inline bool imx6_pcie_supports_suspend(struct imx6_pcie *imx6_pcie)
> +{
> +       return (imx6_pcie->variant == IMX7D ||
> +               imx6_pcie->variant == IMX6SX);
> +}
> +
>  static int imx6_pcie_suspend_noirq(struct device *dev)
>  {
>         struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
>
> -       if (imx6_pcie->variant != IMX7D)
> +       if (!imx6_pcie_supports_suspend(imx6_pcie))
>                 return 0;
>
>         imx6_pcie_pm_turnoff(imx6_pcie);
>         imx6_pcie_clk_disable(imx6_pcie);
>         imx6_pcie_ltssm_disable(dev);
> @@ -817,11 +851,11 @@ static int imx6_pcie_resume_noirq(struct device *dev)
>  {
>         int ret;
>         struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
>         struct pcie_port *pp = &imx6_pcie->pci->pp;
>
> -       if (imx6_pcie->variant != IMX7D)
> +       if (!imx6_pcie_supports_suspend(imx6_pcie))
>                 return 0;
>
>         imx6_pcie_assert_core_reset(imx6_pcie);
>         imx6_pcie_init_phy(imx6_pcie);
>         imx6_pcie_deassert_core_reset(imx6_pcie);
> diff --git a/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h b/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
> index 6c1ad160ed87..c1b25f5e386d 100644
> --- a/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
> +++ b/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
> @@ -438,10 +438,11 @@
>  #define IMX6SX_GPR5_DISP_MUX_DCIC1_LCDIF1              (0x0 << 1)
>  #define IMX6SX_GPR5_DISP_MUX_DCIC1_LVDS                        (0x1 << 1)
>  #define IMX6SX_GPR5_DISP_MUX_DCIC1_MASK                        (0x1 << 1)
>
>  #define IMX6SX_GPR12_PCIE_TEST_POWERDOWN               BIT(30)
> +#define IMX6SX_GPR12_PCIE_PM_TURN_OFF                  BIT(16)
>  #define IMX6SX_GPR12_PCIE_RX_EQ_MASK                   (0x7 << 0)
>  #define IMX6SX_GPR12_PCIE_RX_EQ_2                      (0x2 << 0)
>
>  /* For imx6ul iomux gpr register field define */
>  #define IMX6UL_GPR1_ENET1_CLK_DIR              (0x1 << 17)
> --
> 2.17.1
>