[{"id":3673215,"web_url":"http://patchwork.ozlabs.org/comment/3673215/","msgid":"","list_archive_url":null,"date":"2026-04-03T16:29:46","subject":"Re: [PATCH V10 04/13] PCI: imx6: Assert PERST# before enabling\n regulators","submitter":{"id":78905,"url":"http://patchwork.ozlabs.org/api/people/78905/","name":"Manivannan Sadhasivam","email":"mani@kernel.org"},"content":"On Thu, Apr 02, 2026 at 05:50:58PM +0800, Sherry Sun wrote:\n> According to the PCIe initialization requirements, PERST# signal should\n> be asserted before applying power to the PCIe device, and deasserted\n> after power and reference clock are stable.\n> \n\nSpec wording is not quite like this. Spec mandates asserting PERST# *before*\nstopping refclk and powering down the device and deasserting it *after* applying\npower and refclk stable.\n\nI believe you want to assert PERST# before enabling regulator to prevent the\nendpoint from functioning? If so, is it due to refclk not available yet or some\nother reason?\n\n> Currently, the driver enables the vpcie3v3aux regulator in\n> imx_pcie_probe() before PERST# is asserted in imx_pcie_host_init(),\n> which violates the PCIe power sequencing requirements. However, there\n> is no issue so far because PERST# is requested as GPIOD_OUT_HIGH in\n> imx_pcie_probe(), which guarantees that PERST# is asserted before\n> enabling the vpcie3v3aux regulator.\n> \n> This is prepare for the upcoming changes that will parse the reset\n> property using the new Root Port binding, which will use GPIOD_ASIS\n> when requesting the reset GPIO. With GPIOD_ASIS, the GPIO state is not\n> guaranteed, so explicit sequencing is required.\n> \n> Fix the power sequencing by:\n> 1. Moving vpcie3v3aux regulator enable from probe to\n> imx_pcie_host_init(), where it can be properly sequenced with PERST#.\n> 2. Moving imx_pcie_assert_perst() before regulator and clock enable to\n> ensure correct ordering.\n> \n> The vpcie3v3aux regulator is kept enabled for the entire PCIe controller\n> lifecycle and automatically disabled on device removal via devm cleanup.\n> \n\nvpcie3v3aux handling should be in a separate patch.\n\n- Mani\n\n> Signed-off-by: Sherry Sun \n> ---\n> drivers/pci/controller/dwc/pci-imx6.c | 49 +++++++++++++++++++++------\n> 1 file changed, 39 insertions(+), 10 deletions(-)\n> \n> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c\n> index 45d70ae7e04f..948ffb75d122 100644\n> --- a/drivers/pci/controller/dwc/pci-imx6.c\n> +++ b/drivers/pci/controller/dwc/pci-imx6.c\n> @@ -166,6 +166,8 @@ struct imx_pcie {\n> \tu32\t\t\ttx_swing_full;\n> \tu32\t\t\ttx_swing_low;\n> \tstruct regulator\t*vpcie;\n> +\tstruct regulator\t*vpcie_aux;\n> +\tbool\t\t\tvpcie_aux_enabled;\n> \tstruct regulator\t*vph;\n> \tvoid __iomem\t\t*phy_base;\n> \n> @@ -1220,6 +1222,13 @@ static void imx_pcie_disable_device(struct pci_host_bridge *bridge,\n> \timx_pcie_remove_lut(imx_pcie, pci_dev_id(pdev));\n> }\n> \n> +static void imx_pcie_vpcie_aux_disable(void *data)\n> +{\n> +\tstruct regulator *vpcie_aux = data;\n> +\n> +\tregulator_disable(vpcie_aux);\n> +}\n> +\n> static void imx_pcie_assert_perst(struct imx_pcie *imx_pcie, bool assert)\n> {\n> \tif (assert) {\n> @@ -1240,6 +1249,24 @@ static int imx_pcie_host_init(struct dw_pcie_rp *pp)\n> \tstruct imx_pcie *imx_pcie = to_imx_pcie(pci);\n> \tint ret;\n> \n> +\timx_pcie_assert_perst(imx_pcie, true);\n> +\n> +\t/* Keep 3.3Vaux supply enabled for the entire PCIe controller lifecycle */\n> +\tif (imx_pcie->vpcie_aux && !imx_pcie->vpcie_aux_enabled) {\n> +\t\tret = regulator_enable(imx_pcie->vpcie_aux);\n> +\t\tif (ret) {\n> +\t\t\tdev_err(dev, \"failed to enable vpcie_aux regulator: %d\\n\",\n> +\t\t\t\tret);\n> +\t\t\treturn ret;\n> +\t\t}\n> +\t\timx_pcie->vpcie_aux_enabled = true;\n> +\n> +\t\tret = devm_add_action_or_reset(dev, imx_pcie_vpcie_aux_disable,\n> +\t\t\t\t\t imx_pcie->vpcie_aux);\n> +\t\tif (ret)\n> +\t\t\treturn ret;\n> +\t}\n> +\n> \tif (imx_pcie->vpcie) {\n> \t\tret = regulator_enable(imx_pcie->vpcie);\n> \t\tif (ret) {\n> @@ -1249,25 +1276,24 @@ static int imx_pcie_host_init(struct dw_pcie_rp *pp)\n> \t\t}\n> \t}\n> \n> +\tret = imx_pcie_clk_enable(imx_pcie);\n> +\tif (ret) {\n> +\t\tdev_err(dev, \"unable to enable pcie clocks: %d\\n\", ret);\n> +\t\tgoto err_reg_disable;\n> +\t}\n> +\n> \tif (pp->bridge && imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_LUT)) {\n> \t\tpp->bridge->enable_device = imx_pcie_enable_device;\n> \t\tpp->bridge->disable_device = imx_pcie_disable_device;\n> \t}\n> \n> \timx_pcie_assert_core_reset(imx_pcie);\n> -\timx_pcie_assert_perst(imx_pcie, true);\n> \n> \tif (imx_pcie->drvdata->init_phy)\n> \t\timx_pcie->drvdata->init_phy(imx_pcie);\n> \n> \timx_pcie_configure_type(imx_pcie);\n> \n> -\tret = imx_pcie_clk_enable(imx_pcie);\n> -\tif (ret) {\n> -\t\tdev_err(dev, \"unable to enable pcie clocks: %d\\n\", ret);\n> -\t\tgoto err_reg_disable;\n> -\t}\n> -\n> \tif (imx_pcie->phy) {\n> \t\tret = phy_init(imx_pcie->phy);\n> \t\tif (ret) {\n> @@ -1780,9 +1806,12 @@ static int imx_pcie_probe(struct platform_device *pdev)\n> \tof_property_read_u32(node, \"fsl,max-link-speed\", &pci->max_link_speed);\n> \timx_pcie->supports_clkreq = of_property_read_bool(node, \"supports-clkreq\");\n> \n> -\tret = devm_regulator_get_enable_optional(&pdev->dev, \"vpcie3v3aux\");\n> -\tif (ret < 0 && ret != -ENODEV)\n> -\t\treturn dev_err_probe(dev, ret, \"failed to enable Vaux supply\\n\");\n> +\timx_pcie->vpcie_aux = devm_regulator_get_optional(&pdev->dev, \"vpcie3v3aux\");\n> +\tif (IS_ERR(imx_pcie->vpcie_aux)) {\n> +\t\tif (PTR_ERR(imx_pcie->vpcie_aux) != -ENODEV)\n> +\t\t\treturn PTR_ERR(imx_pcie->vpcie_aux);\n> +\t\timx_pcie->vpcie_aux = NULL;\n> +\t}\n> \n> \timx_pcie->vpcie = devm_regulator_get_optional(&pdev->dev, \"vpcie\");\n> \tif (IS_ERR(imx_pcie->vpcie)) {\n> -- \n> 2.37.1\n>","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=d3t2+OAH;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.105.105.114; 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