RE: [PATCH] PCI: imx6: Separate PERST# assertion from core reset functions

[Hongxing Zhu]

> -----Original Message-----
> From: Sherry Sun <sherry.sun@xxxxxxx>
> Sent: 2026年3月6日 11:05
> To: Hongxing Zhu <hongxing.zhu@xxxxxxx>; l.stach@xxxxxxxxxxxxxx; Frank
> Li <frank.li@xxxxxxx>; bhelgaas@xxxxxxxxxx; lpieralisi@xxxxxxxxxx;
> kwilczynski@xxxxxxxxxx; mani@xxxxxxxxxx; robh@xxxxxxxxxx;
> s.hauer@xxxxxxxxxxxxxx; festevam@xxxxxxxxx
> Cc: imx@xxxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH] PCI: imx6: Separate PERST# assertion from core reset
> functions
> 
> The imx_pcie_assert_core_reset() and imx_pcie_deassert_core_reset()
> functions are primarily intended to reset the RC controller itself, not the
> remote PCIe endpoint devices. However, the PERST# GPIO control was
> previously embedded within these functions, which conflates two distinct
> reset operations.
> 
> Move the PERST# GPIO handling into a dedicated function
> imx_pcie_assert_perst(). This makes the code more maintainable and
> prepares for parsing the reset-gpios property according to the new Root
> Port DT binding in subsequent patches.
> 
> No functional change is intended.
> 
> Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
Reviewed-by: Richard Zhu <hongxing.zhu@xxxxxxx>

Best Regards
Richard Zhu
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 29 +++++++++++++++++----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> b/drivers/pci/controller/dwc/pci-imx6.c
> index ba6e7c7ee625..d80d3be28ee5 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -901,9 +901,6 @@ static void imx_pcie_assert_core_reset(struct
> imx_pcie *imx_pcie)
> 
>  	if (imx_pcie->drvdata->core_reset)
>  		imx_pcie->drvdata->core_reset(imx_pcie, true);
> -
> -	/* Some boards don't have PCIe reset GPIO. */
> -	gpiod_set_value_cansleep(imx_pcie->reset_gpiod, 1);
>  }
> 
>  static void imx_pcie_deassert_core_reset(struct imx_pcie *imx_pcie) @@
> -912,14 +909,6 @@ static void imx_pcie_deassert_core_reset(struct
> imx_pcie *imx_pcie)
> 
>  	if (imx_pcie->drvdata->core_reset)
>  		imx_pcie->drvdata->core_reset(imx_pcie, false);
> -
> -	/* Some boards don't have PCIe reset GPIO. */
> -	if (imx_pcie->reset_gpiod) {
> -		msleep(100);
> -		gpiod_set_value_cansleep(imx_pcie->reset_gpiod, 0);
> -		/* Wait for 100ms after PERST# deassertion (PCIe r5.0, 6.6.1) */
> -		msleep(100);
> -	}
>  }
> 
>  static int imx_pcie_wait_for_speed_change(struct imx_pcie *imx_pcie) @@
> -1231,6 +1220,19 @@ static void imx_pcie_disable_device(struct
> pci_host_bridge *bridge,
>  	imx_pcie_remove_lut(imx_pcie, pci_dev_id(pdev));  }
> 
> +static void imx_pcie_assert_perst(struct imx_pcie *imx_pcie, bool
> +assert) {
> +	if (assert) {
> +		gpiod_set_value_cansleep(imx_pcie->reset_gpiod, 1);
> +	} else {
> +		if (imx_pcie->reset_gpiod) {
> +			msleep(PCIE_T_PVPERL_MS);
> +			gpiod_set_value_cansleep(imx_pcie->reset_gpiod, 0);
> +			msleep(PCIE_RESET_CONFIG_WAIT_MS);
> +		}
> +	}
> +}
> +
>  static int imx_pcie_host_init(struct dw_pcie_rp *pp)  {
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp); @@ -1253,6 +1255,7
> @@ static int imx_pcie_host_init(struct dw_pcie_rp *pp)
>  	}
> 
>  	imx_pcie_assert_core_reset(imx_pcie);
> +	imx_pcie_assert_perst(imx_pcie, true);
> 
>  	if (imx_pcie->drvdata->init_phy)
>  		imx_pcie->drvdata->init_phy(imx_pcie);
> @@ -1291,6 +1294,7 @@ static int imx_pcie_host_init(struct dw_pcie_rp
> *pp)
>  	imx_pcie_ltssm_disable(dev);
> 
>  	imx_pcie_deassert_core_reset(imx_pcie);
> +	imx_pcie_assert_perst(imx_pcie, false);
> 
>  	if (imx_pcie->drvdata->wait_pll_lock) {
>  		ret = imx_pcie->drvdata->wait_pll_lock(imx_pcie);
> @@ -1587,6 +1591,7 @@ static int imx_pcie_suspend_noirq(struct device
> *dev)
>  		 * clock which saves some power.
>  		 */
>  		imx_pcie_assert_core_reset(imx_pcie);
> +		imx_pcie_assert_perst(imx_pcie, true);
>  		imx_pcie->drvdata->enable_ref_clk(imx_pcie, false);
>  	} else {
>  		return dw_pcie_suspend_noirq(imx_pcie->pci);
> @@ -1608,6 +1613,7 @@ static int imx_pcie_resume_noirq(struct device
> *dev)
>  		if (ret)
>  			return ret;
>  		imx_pcie_deassert_core_reset(imx_pcie);
> +		imx_pcie_assert_perst(imx_pcie, false);
> 
>  		/*
>  		 * Using PCIE_TEST_PD seems to disable MSI and powers down the
> @@ -1845,6 +1851,7 @@ static void imx_pcie_shutdown(struct
> platform_device *pdev)
> 
>  	/* bring down link, so bootloader gets clean state in case of reboot */
>  	imx_pcie_assert_core_reset(imx_pcie);
> +	imx_pcie_assert_perst(imx_pcie, true);
>  }
> 
>  static const struct imx_pcie_drvdata drvdata[] = {
> --
> 2.37.1