Re: [PATCH v1 2/5] PCI: imx6: Toggle the cold reset for i.MX95 PCIe

[Frank Li]

On Mon, Mar 24, 2025 at 02:26:44PM +0800, Richard Zhu wrote:
> Beside the power-on reset, add the cold reset toggle for i.MX95 PCIe.

Add the code reset toggle for i.MX95 PCIe to align PHY's power on sequency.

>
> Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 31 +++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index aa5c3f235995..0f42ab63f5ad 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -71,6 +71,9 @@
>  #define IMX95_SID_MASK				GENMASK(5, 0)
>  #define IMX95_MAX_LUT				32
>
> +#define IMX95_PCIE_RST_CTRL			0x3010
> +#define IMX95_PCIE_COLD_RST			BIT(0)
> +
>  #define to_imx_pcie(x)	dev_get_drvdata((x)->dev)
>
>  enum imx_pcie_variants {
> @@ -773,6 +776,32 @@ static int imx7d_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
>  	return 0;
>  }
>
> +static int imx95_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +{
> +	if (assert) {
> +		/*
> +		 * From i.MX95 PCIe PHY perspective, the COLD reset toggle
> +		 * should be complete after power-up by the following sequence.
> +		 *                 > 10us(at power-up)
> +		 *                 > 10ns(warm reset)
> +		 *               |<------------>|
> +		 *                ______________
> +		 * phy_reset ____/              \________________
> +		 *                                   ____________
> +		 * ref_clk_en_______________________/
> +		 * Toggle COLD reset aligned with this sequence for i.MX95 PCIe.
> +		 */
> +		regmap_update_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
> +				   IMX95_PCIE_COLD_RST, IMX95_PCIE_COLD_RST);

regmap_set_bits()

> +		udelay(15);

udelay may not use MMIO. It cause delay time less than 15us. Need read one
register before udelay(15);

> +		regmap_update_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
> +				   IMX95_PCIE_COLD_RST, 0);

regmap_clr_bits();

Frank

> +		udelay(10);
> +	}
> +
> +	return 0;
> +}
> +
>  static void imx_pcie_assert_core_reset(struct imx_pcie *imx_pcie)
>  {
>  	reset_control_assert(imx_pcie->pciephy_reset);
> @@ -1762,6 +1791,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.ltssm_mask = IMX95_PCIE_LTSSM_EN,
>  		.mode_off[0]  = IMX95_PE0_GEN_CTRL_1,
>  		.mode_mask[0] = IMX95_PCIE_DEVICE_TYPE,
> +		.core_reset = imx95_pcie_core_reset,
>  		.init_phy = imx95_pcie_init_phy,
>  	},
>  	[IMX8MQ_EP] = {
> @@ -1815,6 +1845,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.mode_off[0]  = IMX95_PE0_GEN_CTRL_1,
>  		.mode_mask[0] = IMX95_PCIE_DEVICE_TYPE,
>  		.init_phy = imx95_pcie_init_phy,
> +		.core_reset = imx95_pcie_core_reset,
>  		.epc_features = &imx95_pcie_epc_features,
>  		.mode = DW_PCIE_EP_TYPE,
>  	},
> --
> 2.37.1
>