linux-kernel - Re: [PATCH v1 5/5] PCI: imx6: Save and restore the LUT setting for i.MX95 PCIe

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Message-ID: <Z+Gw3g0FfytALdRo@lizhi-Precision-Tower-5810>
Date: Mon, 24 Mar 2025 15:22:06 -0400
From: Frank Li <Frank.li@....com>
To: Richard Zhu <hongxing.zhu@....com>
Cc: l.stach@...gutronix.de, lpieralisi@...nel.org, kw@...ux.com,
	manivannan.sadhasivam@...aro.org, robh@...nel.org,
	bhelgaas@...gle.com, shawnguo@...nel.org, s.hauer@...gutronix.de,
	kernel@...gutronix.de, festevam@...il.com,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 5/5] PCI: imx6: Save and restore the LUT setting for
 i.MX95 PCIe

On Mon, Mar 24, 2025 at 02:26:47PM +0800, Richard Zhu wrote:
> LUT(look up table) setting would be lost during PCIe suspend on i.MX95.
>
> To let i.MX95 PCIe PM work fine, save and restore the LUT setting in
> suspend and resume operations.
>
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 46 +++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index dda3eed99bb8..a3a032cbaa3c 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -135,6 +135,11 @@ struct imx_pcie_drvdata {
>  	const struct dw_pcie_host_ops *ops;
>  };
>
> +struct imx_lut_data {
> +	u32 data1;
> +	u32 data2;
> +};
> +
>  struct imx_pcie {
>  	struct dw_pcie		*pci;
>  	struct gpio_desc	*reset_gpiod;
> @@ -154,6 +159,8 @@ struct imx_pcie {
>  	struct regulator	*vph;
>  	void __iomem		*phy_base;
>
> +	/* LUT data for pcie */
> +	struct imx_lut_data	luts[IMX95_MAX_LUT];
>  	/* power domain for pcie */
>  	struct device		*pd_pcie;
>  	/* power domain for pcie phy */
> @@ -1468,6 +1475,41 @@ static void imx_pcie_msi_save_restore(struct imx_pcie *imx_pcie, bool save)
>  	}
>  }
>
> +static void imx_pcie_lut_save_restore(struct imx_pcie *imx_pcie, bool save)
> +{
> +	int i;
> +	u32 data1, data2;

Reverse Christmas order.

> +
> +	for (i = 0; i < IMX95_MAX_LUT; i++) {
> +		if (save) {
> +			regmap_write(imx_pcie->iomuxc_gpr,
> +				     IMX95_PE0_LUT_ACSCTRL,
> +				     IMX95_PEO_LUT_RWA | i);
> +			regmap_read(imx_pcie->iomuxc_gpr,
> +				    IMX95_PE0_LUT_DATA1, &data1);
> +			regmap_read(imx_pcie->iomuxc_gpr,
> +				    IMX95_PE0_LUT_DATA2, &data2);
> +			if (data1 & IMX95_PE0_LUT_VLD) {
> +				imx_pcie->luts[i].data1 = data1;
> +				imx_pcie->luts[i].data2 = data2;
> +			} else {
> +				imx_pcie->luts[i].data1 = 0;
> +				imx_pcie->luts[i].data2 = 0;
> +			}

Almost no shared part between save and restore. Suggest use two helper
function imx_pcie_lut_save() and imx_pcie_lut_restore().

Frank

> +		} else {
> +			if ((imx_pcie->luts[i].data1 & IMX95_PE0_LUT_VLD) == 0)
> +				continue;
> +
> +			regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA1,
> +				     imx_pcie->luts[i].data1);
> +			regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA2,
> +				     imx_pcie->luts[i].data2);
> +			regmap_write(imx_pcie->iomuxc_gpr,
> +				     IMX95_PE0_LUT_ACSCTRL, i);
> +		}
> +	}
> +}
> +
>  static int imx_pcie_suspend_noirq(struct device *dev)
>  {
>  	struct imx_pcie *imx_pcie = dev_get_drvdata(dev);
> @@ -1476,6 +1518,8 @@ static int imx_pcie_suspend_noirq(struct device *dev)
>  		return 0;
>
>  	imx_pcie_msi_save_restore(imx_pcie, true);
> +	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_LUT))
> +		imx_pcie_lut_save_restore(imx_pcie, true);
>  	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_BROKEN_SUSPEND)) {
>  		/*
>  		 * The minimum for a workaround would be to set PERST# and to
> @@ -1520,6 +1564,8 @@ static int imx_pcie_resume_noirq(struct device *dev)
>  		if (ret)
>  			return ret;
>  	}
> +	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_LUT))
> +		imx_pcie_lut_save_restore(imx_pcie, false);
>  	imx_pcie_msi_save_restore(imx_pcie, false);
>
>  	return 0;
> --
> 2.37.1
>