linux-kernel - Re: [PATCH v6 7/8] PCI: imx6: Disable enabled clocks and regulators after link is down

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Message-ID: <CAOMZO5ALthc7zZEYZX2YHam2f3C1RmOr4CHLRjHSip7-44tL6Q@mail.gmail.com>
Date:   Tue, 8 Feb 2022 07:09:40 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Richard Zhu <hongxing.zhu@....com>
Cc:     Lucas Stach <l.stach@...gutronix.de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mark Brown <broonie@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jingoo Han <jingoohan1@...il.com>, linux-pci@...r.kernel.org,
        NXP Linux Team <linux-imx@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH v6 7/8] PCI: imx6: Disable enabled clocks and regulators
 after link is down

Hi Richard,

On Tue, Feb 8, 2022 at 12:57 AM Richard Zhu <hongxing.zhu@....com> wrote:
>
> Since i.MX PCIe doesn't support the hot-plug, and to save power
> consumption as much as possible. Return error and disable the enabled
> clocks and regulators when link is down,.

It is OK to disable clocks and regulators, but I don't think we should
return an error on dw_pcie_wait_for_link() failure.

Please check:

https://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/pci.git/commit/?h=pci/imx6&id=f81f095e87715e198471f4653952fe5e3f824874

and

https://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/pci.git/commit/?h=pci/imx6&id=886a9c134755

as to why all the dwc PCI drivers should treat dw_pcie_wait_for_link()
uniformly.






>
> Add a new host_exit() callback for i.MX PCIe driver to disable the
> enabled clocks, regulators and so on in the error handling after
> host_init is finished.
>
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 30 ++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index e165ad00989c..7a7d9204c6bc 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -848,7 +848,9 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>         /* Start LTSSM. */
>         imx6_pcie_ltssm_enable(dev);
>
> -       dw_pcie_wait_for_link(pci);
> +       ret = dw_pcie_wait_for_link(pci);
> +       if (ret)
> +               goto err_reset_phy;
>
>         if (pci->link_gen == 2) {
>                 /* Allow Gen2 mode after the link is up. */
> @@ -884,7 +886,9 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>                 }
>
>                 /* Make sure link training is finished as well! */
> -               dw_pcie_wait_for_link(pci);
> +               ret = dw_pcie_wait_for_link(pci);
> +               if (ret)
> +                       goto err_reset_phy;
>         } else {
>                 dev_info(dev, "Link: Gen2 disabled\n");
>         }
> @@ -897,7 +901,6 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>         dev_dbg(dev, "PHY DEBUG_R0=0x%08x DEBUG_R1=0x%08x\n",
>                 dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG0),
>                 dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG1));
> -       imx6_pcie_reset_phy(imx6_pcie);
>         return ret;
>  }
>
> @@ -921,8 +924,29 @@ static int imx6_pcie_host_init(struct pcie_port *pp)
>         return 0;
>  }
>
> +static void imx6_pcie_host_exit(struct pcie_port *pp)
> +{
> +       struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +       struct device *dev = pci->dev;
> +       struct imx6_pcie *imx6_pcie = to_imx6_pcie(pci);
> +
> +       imx6_pcie_reset_phy(imx6_pcie);
> +       imx6_pcie_clk_disable(imx6_pcie);
> +       switch (imx6_pcie->drvdata->variant) {
> +       case IMX8MM:
> +               if (phy_power_off(imx6_pcie->phy))
> +                       dev_err(dev, "unable to power off phy\n");
> +               break;
> +       default:
> +               break;
> +       }
> +       if (imx6_pcie->vpcie)
> +               regulator_disable(imx6_pcie->vpcie);
> +}
> +
>  static const struct dw_pcie_host_ops imx6_pcie_host_ops = {
>         .host_init = imx6_pcie_host_init,
> +       .host_exit = imx6_pcie_host_exit,
>  };
>
>  static const struct dw_pcie_ops dw_pcie_ops = {
> --
> 2.25.1
>