Re: [PATCH V11 04/12] PCI: imx6: Add support for parsing the reset property in new Root Port binding

Manivannan Sadhasivam
2026-04-08T13:55:36Z

On Wed, Apr 08, 2026 at 08:34:03AM +0000, Sherry Sun wrote:
> > On Tue, Apr 07, 2026 at 06:41:46PM +0800, Sherry Sun wrote:
> > > The current DT binding for pci-imx6 specifies the 'reset-gpios'
> > > property in the host bridge node. However, the PERST# signal logically
> > > belongs to individual Root Ports rather than the host bridge itself.
> > > This becomes important when supporting PCIe KeyE connector and PCI
> > > power control framework for pci-imx6 driver, which requires properties
> > > to be specified in Root Port nodes.
> > >
> > > Add support for parsing 'reset-gpios' from Root Port child nodes using
> > > the common helper pci_host_common_parse_ports(), and update the reset
> > > GPIO handling to use the parsed port list from bridge->ports. 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.
> > >
> > > Since now the reset GPIO is obtained with GPIOD_ASIS flag, it may be
> > > in input mode, using gpiod_direction_output() instead of
> > > gpiod_set_value_cansleep() to ensure the reset GPIO is properly
> > > configured as output before setting its value.
> > >
> > > Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
> > > ---
> > > drivers/pci/controller/dwc/pci-imx6.c | 75
> > > +++++++++++++++++++++------
> > > 1 file changed, 60 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > index d99da7e42590..dd8f9c0fcec4 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)
> > > @@ -152,7 +153,6 @@ struct imx_lut_data {
> > >
> > > struct imx_pcie {
> > > struct dw_pcie *pci;
> > > - struct gpio_desc *reset_gpiod;
> > > struct clk_bulk_data *clks;
> > > int num_clks;
> > > bool supports_clkreq;
> > > @@ -1224,6 +1224,32 @@ static void imx_pcie_disable_device(struct
> > pci_host_bridge *bridge,
> > > imx_pcie_remove_lut(imx_pcie, pci_dev_id(pdev)); }
> > >
> > > +static int imx_pcie_parse_legacy_binding(struct imx_pcie *pcie) {
> > > + struct device *dev = pcie->pci->dev;
> > > + struct pci_host_bridge *bridge = pcie->pci->pp.bridge;
> > > + struct pci_host_port *port;
> > > + struct gpio_desc *reset;
> > > +
> > > + reset = devm_gpiod_get_optional(dev, "reset", GPIOD_ASIS);
> > > + if (IS_ERR(reset))
> > > + return PTR_ERR(reset);
> > > +
> > > + if (!reset)
> > > + return 0;
> > > +
> > > + 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, &bridge->ports);
> > > +
> > > + return devm_add_action_or_reset(dev,
> > pci_host_common_delete_ports,
> > > + &bridge->ports);
> > > +}
> > > +
> > > static void imx_pcie_vpcie_aux_disable(void *data) {
> > > struct regulator *vpcie_aux = data;
> > > @@ -1233,13 +1259,22 @@ static void imx_pcie_vpcie_aux_disable(void
> > > *data)
> > >
> > > 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);
> > > + struct dw_pcie *pci = imx_pcie->pci;
> > > + struct pci_host_bridge *bridge = pci->pp.bridge;
> > > + struct pci_host_port *port;
> > > +
> > > + if (!bridge)
> > > + return;
> > > +
> > > + list_for_each_entry(port, &bridge->ports, list) {
> > > + if (assert) {
> > > + gpiod_direction_output(port->reset, 1);
> > > + } else {
> > > + if (port->reset) {
> > > + msleep(PCIE_T_PVPERL_MS);
> > > + gpiod_direction_output(port->reset, 0);
> > > + msleep(PCIE_RESET_CONFIG_WAIT_MS);
> > > + }
> >
> > Sashiko flagged this loop:
> >
> > ```
> > Does this loop multiply the initialization delays?
> > If a controller has multiple Root Ports, the msleep calls will run sequentially
> > for each port, linearly increasing the delay. Could we optimize this by
> > asserting all reset GPIOs, waiting the pre-delay once, de-asserting all GPIOs,
> > and waiting the post-delay once for the entire bus?
> > ```
> >
> > Maybe you should do:
> >
> > if (!list_empty(&bridge->ports) && !assert)
> > msleep(PCIE_T_PVPERL_MS);
> >
> > list_for_each_entry(port, &bridge->ports, list) {
> > ...
> > gpiod_direction_output(port->reset, 0);
> > ...
> > }
> >
> > if (!list_empty(&bridge->ports) && !assert)
> > msleep(PCIE_RESET_CONFIG_WAIT_MS);
> >
>
> Hi Mani, I think the code below looks clearer, is that ok for you?
>
> if (assert) {
> list_for_each_entry(port, &bridge->ports, list)
> gpiod_direction_output(port->reset, 1);
> } else {
> if (list_empty(&bridge->ports))
> return;
>

This check should be moved out of the if() condition. Other than this, the
change looks good.

> msleep(PCIE_T_PVPERL_MS);
> list_for_each_entry(port, &bridge->ports, list)
> gpiod_direction_output(port->reset, 0);
> msleep(PCIE_RESET_CONFIG_WAIT_MS);
> }
>
> > And then this:
> >
> > ```
> > Also, since this function is called from imx_pcie_resume_noirq, which
> > executes with hardware interrupts disabled, does the use of msleep here
> > trigger a 'sleeping while atomic' bug?
> > ```
> >
> > This is a valid concern. You should use mdelay(). But I'd recommend switching
> > to IRQ enabled callback, resume() instead. There is no complelling reason to
> > use resume_noirq() in this driver and adding delays in noirq() callbacks is not
> > recommended as it may increase the overall system resume time.
> >
> > I will submit a separate series to convert dw_pcie_resume_noirq() and its
> > callers to IRQ enabled callbacks since this dw_pcie_resume_noirq() could
> > potentially cause delay up to 1sec.
>
> Yes, this is not a new bug introduced by this patch. I agree we should covert the
> convert dw_pcie_resume_noirq() and the caller to IRQ enabled callbacks to fix
> this in a separate patch series.
> For now, should I leave it as is, or switch to mdelay in this patch?
>

Just use mdelay() in your patch for now.

- Mani

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