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Message-ID:
<DM4PR12MB615857BF931389A86C21E164CD7BA@DM4PR12MB6158.namprd12.prod.outlook.com>
Date: Wed, 25 Jun 2025 04:27:40 +0000
From: "Musham, Sai Krishna" <sai.krishna.musham@....com>
To: Bjorn Helgaas <helgaas@...nel.org>
CC: "bhelgaas@...gle.com" <bhelgaas@...gle.com>, "lpieralisi@...nel.org"
<lpieralisi@...nel.org>, "kw@...ux.com" <kw@...ux.com>, "mani@...nel.org"
<mani@...nel.org>, "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
<krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
"cassel@...nel.org" <cassel@...nel.org>, "linux-pci@...r.kernel.org"
<linux-pci@...r.kernel.org>, "devicetree@...r.kernel.org"
<devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "Simek, Michal" <michal.simek@....com>,
"Gogada, Bharat Kumar" <bharat.kumar.gogada@....com>, "Havalige, Thippeswamy"
<thippeswamy.havalige@....com>
Subject: RE: [PATCH v3 2/2] PCI: amd-mdb: Add support for PCIe RP PERST#
signal handling
[AMD Official Use Only - AMD Internal Distribution Only]
Hi Bjorn,
> -----Original Message-----
> From: Bjorn Helgaas <helgaas@...nel.org>
> Sent: Tuesday, June 24, 2025 9:31 PM
> To: Musham, Sai Krishna <sai.krishna.musham@....com>
> Cc: bhelgaas@...gle.com; lpieralisi@...nel.org; kw@...ux.com; mani@...nel.org;
> robh@...nel.org; krzk+dt@...nel.org; conor+dt@...nel.org; cassel@...nel.org;
> linux-pci@...r.kernel.org; devicetree@...r.kernel.org; linux-
> kernel@...r.kernel.org; Simek, Michal <michal.simek@....com>; Gogada, Bharat
> Kumar <bharat.kumar.gogada@....com>; Havalige, Thippeswamy
> <thippeswamy.havalige@....com>
> Subject: Re: [PATCH v3 2/2] PCI: amd-mdb: Add support for PCIe RP PERST#
> signal handling
>
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
>
>
> On Wed, Jun 18, 2025 at 01:39:31PM +0530, Sai Krishna Musham wrote:
> > Add GPIO based PERST# signal handling for AMD Versal Gen 2 MDB
> > PCIe Root Port.
> >
> > Signed-off-by: Sai Krishna Musham <sai.krishna.musham@....com>
> > ---
> > Changes in v3:
> > - Implement amd_mdb_parse_pcie_port to parse bridge node for reset-gpios
> property.
> >
> > Changes in v2:
> > - Change delay to PCIE_T_PVPERL_MS
>
> v3 https://lore.kernel.org/r/20250618080931.2472366-1-
> sai.krishna.musham@....com/
> v2 https://lore.kernel.org/r/20250429090046.1512000-1-
> sai.krishna.musham@....com/
> v1 https://lore.kernel.org/r/20250326041507.98232-1-
> sai.krishna.musham@....com/
>
Sure, I will add the lore links. Thanks
> > ---
> > drivers/pci/controller/dwc/pcie-amd-mdb.c | 45 ++++++++++++++++++++++-
> > 1 file changed, 44 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-amd-mdb.c
> b/drivers/pci/controller/dwc/pcie-amd-mdb.c
> > index 4eb2a4e8189d..b4c5b71900a5 100644
> > --- a/drivers/pci/controller/dwc/pcie-amd-mdb.c
> > +++ b/drivers/pci/controller/dwc/pcie-amd-mdb.c
> > @@ -18,6 +18,7 @@
> > #include <linux/resource.h>
> > #include <linux/types.h>
> >
> > +#include "../../pci.h"
> > #include "pcie-designware.h"
> >
> > #define AMD_MDB_TLP_IR_STATUS_MISC 0x4C0
> > @@ -63,6 +64,7 @@ struct amd_mdb_pcie {
> > void __iomem *slcr;
> > struct irq_domain *intx_domain;
> > struct irq_domain *mdb_domain;
> > + struct gpio_desc *perst_gpio;
> > int intx_irq;
> > };
> >
> > @@ -284,7 +286,7 @@ static int amd_mdb_pcie_init_irq_domains(struct
> amd_mdb_pcie *pcie,
> > struct device_node *pcie_intc_node;
> > int err;
> >
> > - pcie_intc_node = of_get_next_child(node, NULL);
> > + pcie_intc_node = of_get_child_by_name(node, "interrupt-controller");
>
> Is this change logically part of the PERST# support? If not, this
> could be a separate patch.
>
Yes, this change is logically part of the PERST# support patch.
Previously, the interrupt-controller node was the only child under the PCIe node,
so we used of_get_next_child() to retrieve it. With this patch, a new PCIe bridge
node has been added as a child node, which could lead to ambiguity or incorrect
parsing.
To ensure we explicitly retrieve the correct node and avoid potential issues, I replaced
of_get_next_child() with of_get_child_by_name() to directly access the 'interrupt-controller'
node.
> > if (!pcie_intc_node) {
> > dev_err(dev, "No PCIe Intc node found\n");
> > return -ENODEV;
> > @@ -402,6 +404,34 @@ static int amd_mdb_setup_irq(struct amd_mdb_pcie
> *pcie,
> > return 0;
> > }
> >
> > +static int amd_mdb_parse_pcie_port(struct amd_mdb_pcie *pcie)
> > +{
> > + struct device *dev = pcie->pci.dev;
> > + struct device_node *pcie_port_node;
> > +
> > + pcie_port_node = of_get_next_child_with_prefix(dev->of_node, NULL, "pcie");
> > + if (!pcie_port_node) {
> > + dev_err(dev, "No PCIe Bridge node found\n");
> > + return -ENODEV;
> > + }
> > +
> > + /* Request the GPIO for PCIe reset signal and assert */
> > + pcie->perst_gpio = devm_fwnode_gpiod_get(dev,
> of_fwnode_handle(pcie_port_node),
> > + "reset", GPIOD_OUT_HIGH, NULL);
> > + if (IS_ERR(pcie->perst_gpio)) {
> > + if (PTR_ERR(pcie->perst_gpio) != -ENOENT) {
> > + of_node_put(pcie_port_node);
> > + return dev_err_probe(dev, PTR_ERR(pcie->perst_gpio),
> > + "Failed to request reset GPIO\n");
> > + }
> > + pcie->perst_gpio = NULL;
> > + }
> > +
> > + of_node_put(pcie_port_node);
> > +
> > + return 0;
> > +}
> > +
> > static int amd_mdb_add_pcie_port(struct amd_mdb_pcie *pcie,
> > struct platform_device *pdev)
> > {
> > @@ -426,6 +456,14 @@ static int amd_mdb_add_pcie_port(struct
> amd_mdb_pcie *pcie,
> >
> > pp->ops = &amd_mdb_pcie_host_ops;
> >
> > + if (pcie->perst_gpio) {
> > + mdelay(PCIE_T_PVPERL_MS);
> > +
> > + /* Deassert the reset signal */
> > + gpiod_set_value_cansleep(pcie->perst_gpio, 0);
> > + mdelay(PCIE_T_RRS_READY_MS);
> > + }
> > +
> > err = dw_pcie_host_init(pp);
> > if (err) {
> > dev_err(dev, "Failed to initialize host, err=%d\n", err);
> > @@ -444,6 +482,7 @@ static int amd_mdb_pcie_probe(struct platform_device
> *pdev)
> > struct device *dev = &pdev->dev;
> > struct amd_mdb_pcie *pcie;
> > struct dw_pcie *pci;
> > + int ret;
> >
> > pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
> > if (!pcie)
> > @@ -454,6 +493,10 @@ static int amd_mdb_pcie_probe(struct platform_device
> *pdev)
> >
> > platform_set_drvdata(pdev, pcie);
> >
> > + ret = amd_mdb_parse_pcie_port(pcie);
> > + if (ret)
> > + return ret;
> > +
> > return amd_mdb_add_pcie_port(pcie, pdev);
> > }
> >
> > --
> > 2.43.0
> >
Thanks,
Sai krishna
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