Re: [PATCH v2] PCI: imx6: Fix i.MX6Q/DL boot hang by separating PHY power and reference clock control

[Manivannan Sadhasivam]

On Wed, Jul 08, 2026 at 11:59:27AM +0800, hongxing.zhu@xxxxxxxxxxx wrote:
> From: Richard Zhu <hongxing.zhu@xxxxxxx>
> 
> Commit 610fa91d9863 ("PCI: imx6: Assert PERST# before enabling regulators")
> introduced a boot hang on i.MX6Q/DL variants by changing the initialization
> sequence.
> 
> The issue stems from coupling PHY power (TEST_PD) and reference clock
> (REF_CLK_EN) control in imx6q_pcie_enable_ref_clk(). When these are
> managed together, the timing between PHY power-up and reference clock
> enablement cannot be properly controlled, leading to initialization
> failures.
> 

What is the timing requirement here?

> Fix this by separating the two concerns:
> 
> - Move PHY power control (TEST_PD) to imx6q_pcie_core_reset() where it
>   logically belongs with reset operations. This ensures PHY power state
>   is managed as part of the core reset sequence.
> 
> - Update imx6qp_pcie_core_reset() to call imx6q_pcie_core_reset() for
>   shared PHY power management, avoiding code duplication.
> 
> - Make imx6q_pcie_enable_ref_clk() responsible only for reference clock
>   (REF_CLK_EN) control, simplifying its purpose.
> 
> - Remove the 10us delay workaround from imx6q_pcie_enable_ref_clk() as
>   proper sequencing is now handled by the core_reset functions.
> 
> This refactoring ensures PHY power is controlled during reset
> operations, fixing the boot hang while improving code maintainability.
> 

This patch does too many things at once. Can't you split it and keep the minimal
fix in one patch?

- Mani

> Fixes: 610fa91d9863 ("PCI: imx6: Assert PERST# before enabling regulators")
> Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> ---
> Changes in v2:
> Regarding sashiko's reivew, invoke imx_pcie_assert_core_reset() explicitly
> in error path of imx_pcie_host_init() and imx_pcie_host_exit().
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 45 ++++++++++++---------------
>  1 file changed, 20 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 9406bba36953f..53f3da6ab30d5 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -680,21 +680,12 @@ static int imx_pcie_attach_pd(struct device *dev)
>  
>  static int imx6q_pcie_enable_ref_clk(struct imx_pcie *imx_pcie, bool enable)
>  {
> -	if (enable) {
> -		/* power up core phy and enable ref clock */
> -		regmap_clear_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_TEST_PD);
> -		/*
> -		 * The async reset input need ref clock to sync internally,
> -		 * when the ref clock comes after reset, internal synced
> -		 * reset time is too short, cannot meet the requirement.
> -		 * Add a ~10us delay here.
> -		 */
> -		usleep_range(10, 100);
> -		regmap_set_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_REF_CLK_EN);
> -	} else {
> -		regmap_clear_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_REF_CLK_EN);
> -		regmap_set_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_TEST_PD);
> -	}
> +	if (enable)
> +		regmap_set_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1,
> +				IMX6Q_GPR1_PCIE_REF_CLK_EN);
> +	else
> +		regmap_clear_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1,
> +				  IMX6Q_GPR1_PCIE_REF_CLK_EN);
>  
>  	return 0;
>  }
> @@ -823,23 +814,25 @@ static int imx6sx_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
>  	return 0;
>  }
>  
> -static int imx6qp_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +static int imx6q_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
>  {
> -	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_SW_RST,
> -			   assert ? IMX6Q_GPR1_PCIE_SW_RST : 0);
> -	if (!assert)
> -		usleep_range(200, 500);
> +	if (assert)
> +		regmap_set_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1,
> +				IMX6Q_GPR1_PCIE_TEST_PD);
> +	else
> +		regmap_clear_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1,
> +				  IMX6Q_GPR1_PCIE_TEST_PD);
>  
>  	return 0;
>  }
>  
> -static int imx6q_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +static int imx6qp_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
>  {
> +	imx6q_pcie_core_reset(imx_pcie, assert);
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_SW_RST,
> +			   assert ? IMX6Q_GPR1_PCIE_SW_RST : 0);
>  	if (!assert)
> -		return 0;
> -
> -	regmap_set_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_TEST_PD);
> -	regmap_set_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_REF_CLK_EN);
> +		usleep_range(200, 500);
>  
>  	return 0;
>  }
> @@ -1445,6 +1438,7 @@ static int imx_pcie_host_init(struct dw_pcie_rp *pp)
>  	return 0;
>  
>  err_phy_off:
> +	imx_pcie_assert_core_reset(imx_pcie);
>  	phy_power_off(imx_pcie->phy);
>  err_phy_exit:
>  	phy_exit(imx_pcie->phy);
> @@ -1471,6 +1465,7 @@ static void imx_pcie_host_exit(struct dw_pcie_rp *pp)
>  			dev_err(pci->dev, "unable to power off PHY\n");
>  		phy_exit(imx_pcie->phy);
>  	}
> +	imx_pcie_assert_core_reset(imx_pcie);
>  	imx_pcie_clk_disable(imx_pcie);
>  
>  	pci_pwrctrl_power_off_devices(pci->dev);
> -- 
> 2.34.1
> 

-- 
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