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Message-ID: <aYoMzM4omurMaJw5@lizhi-Precision-Tower-5810>
Date: Mon, 9 Feb 2026 11:35:24 -0500
From: Frank Li <Frank.li@....com>
To: Sherry Sun <sherry.sun@....com>
Cc: hongxing.zhu@....com, l.stach@...gutronix.de, bhelgaas@...gle.com,
lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
s.hauer@...gutronix.de, festevam@...il.com, will@...nel.org,
imx@...ts.linux.dev, kernel@...gutronix.de,
linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 03/11] PCI: imx6: Add support for parsing the reset
property in new Root Port binding
On Mon, Feb 09, 2026 at 04:24:46PM +0800, Sherry Sun wrote:
> DT binding allows specifying 'reset' property in both host bridge and
> Root Port nodes, but specifying in the host bridge node is marked as
> deprecated. So add support for parsing the new binding that uses
> 'reset-gpios' property for PERST#.
>
> The initial idea is to add the PCIe M.2 KeyE connector support and PCI
> power control framework to the pcie-imx6 driver. Since the new
> M.2/pwrctrl model is implemented based on Root Ports and requires the
> pwrctrl driver to bind to a Root Port device, we need to introduce a
> Root Port child node on i.MX boards that provide an M.2 connector.
>
> To follow a more standardized DT structure, it also makes sense to move
> the reset-gpios and wake-gpios properties into the Root Port node. These
> signals logically belong to the Root Port rather than the host bridge,
> and placing them there aligns with the new M.2/pwrctrl model.
>
> To maintain DT backwards compatibility, fallback to the legacy method of
> parsing the host bridge node if the reset property is not present in the
> Root Port node.
>
> Signed-off-by: Sherry Sun <sherry.sun@....com>
> ---
> drivers/pci/controller/dwc/pci-imx6.c | 69 +++++++++++++++++++++------
> 1 file changed, 55 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index a5b8d0b71677..317a969da96b 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -34,6 +34,7 @@
> #include <linux/pm_runtime.h>
>
> #include "../../pci.h"
> +#include "../pci-host-common.h"
> #include "pcie-designware.h"
>
> #define IMX8MQ_GPR_PCIE_REF_USE_PAD BIT(9)
> @@ -150,8 +151,8 @@ struct imx_lut_data {
>
> struct imx_pcie {
> struct dw_pcie *pci;
> - struct gpio_desc *reset_gpiod;
> struct clk_bulk_data *clks;
> + struct list_head ports;
> int num_clks;
> bool supports_clkreq;
> bool enable_ext_refclk;
> @@ -897,29 +898,34 @@ static int imx95_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
>
> static void imx_pcie_assert_core_reset(struct imx_pcie *imx_pcie)
> {
> + struct pci_host_port *port;
> +
> reset_control_assert(imx_pcie->pciephy_reset);
>
> 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);
> + list_for_each_entry(port, &imx_pcie->ports, list)
> + gpiod_set_value_cansleep(port->reset, 1);
> }
>
> static int imx_pcie_deassert_core_reset(struct imx_pcie *imx_pcie)
> {
> + struct pci_host_port *port;
> +
> reset_control_deassert(imx_pcie->pciephy_reset);
>
> 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);
> - }
> + list_for_each_entry(port, &imx_pcie->ports, list)
> + if (port->reset) {
> + msleep(PCIE_T_PVPERL_MS);
> + gpiod_set_value_cansleep(port->reset, 0);
> + msleep(PCIE_RESET_CONFIG_WAIT_MS);
> + }
>
> return 0;
> }
> @@ -1642,6 +1648,27 @@ static const struct dev_pm_ops imx_pcie_pm_ops = {
> imx_pcie_resume_noirq)
> };
>
> +static int imx_pcie_parse_legacy_binding(struct imx_pcie *pcie)
> +{
> + struct device *dev = pcie->pci->dev;
> + struct pci_host_port *port;
> + struct gpio_desc *reset;
> +
> + reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
> + if (IS_ERR(reset))
> + return PTR_ERR(reset);
> +
> + port = devm_kzalloc(dev, sizeof(*port), GFP_KERNEL);
> + if (!port)
> + return -ENOMEM;
> +
> + port->reset = reset;
> + INIT_LIST_HEAD(&port->list);
> + list_add_tail(&port->list, &pcie->ports);
> +
> + return 0;
> +}
> +
> static int imx_pcie_probe(struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> @@ -1660,6 +1687,8 @@ static int imx_pcie_probe(struct platform_device *pdev)
> if (!pci)
> return -ENOMEM;
>
> + INIT_LIST_HEAD(&imx_pcie->ports);
> +
> pci->dev = dev;
> pci->ops = &dw_pcie_ops;
>
> @@ -1688,12 +1717,24 @@ static int imx_pcie_probe(struct platform_device *pdev)
> return PTR_ERR(imx_pcie->phy_base);
> }
>
> - /* Fetch GPIOs */
> - imx_pcie->reset_gpiod = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
> - if (IS_ERR(imx_pcie->reset_gpiod))
> - return dev_err_probe(dev, PTR_ERR(imx_pcie->reset_gpiod),
> - "unable to get reset gpio\n");
> - gpiod_set_consumer_name(imx_pcie->reset_gpiod, "PCIe reset");
> + ret = pci_host_common_parse_ports(dev, &imx_pcie->ports);
if API provided pcim_host_common_parse_ports(), needn't below
devm_add_action_or_reset().
Frank.
> + if (ret) {
> + if (ret != -ENOENT)
> + return dev_err_probe(dev, ret, "Failed to parse Root Port: %d\n", ret);
> +
> + /*
> + * In the case of properties not populated in Root Port node,
> + * fallback to the legacy method of parsing the Host Bridge
> + * node. This is to maintain DT backwards compatibility.
> + */
> + ret = imx_pcie_parse_legacy_binding(imx_pcie);
> + if (ret)
> + return dev_err_probe(dev, ret, "Unable to get reset gpio: %d\n", ret);
> + }
> +
> + ret = devm_add_action_or_reset(dev, pci_host_common_delete_ports, &imx_pcie->ports);
> + if (ret)
> + return ret;
>
> /* Fetch clocks */
> imx_pcie->num_clks = devm_clk_bulk_get_all(dev, &imx_pcie->clks);
> --
> 2.37.1
>
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