[PATCH] usb: cdnsp: Add support for device-only configuration

Pawel Laszczak via B4 Relay
2026-03-31T08:05:13Z

From: Pawel Laszczak <pawell@cadence.com>

This patch introduces support for operating the Cadence USBSSP (cdnsp)
controller in a peripheral-only mode, bypassing the Dual-Role Device (DRD)
logic.

The change in BAR indexing (from BAR 2 to BAR 1) is a direct
consequence of switching from 64-bit to 32-bit addressing in the
Peripheral-only configuration.

Tested on PCI platform with Device-only configuration. Platform-side
changes are included to support the PCI glue layer's property injection.

Signed-off-by: Pawel Laszczak <pawell@cadence.com>
---
NOTE: This patch depends on Peter Chen's series "usb: cdns3: Add
USBSSP platform driver support", which was recently accepted by
Greg into the usb-testing branch (commit 6076388ca1ed).
---
drivers/usb/cdns3/cdns3-plat.c | 24 ++++++++++++---------
drivers/usb/cdns3/cdnsp-pci.c | 47 ++++++++++++++++++++++++++++++++++--------
drivers/usb/cdns3/core.c | 3 ++-
drivers/usb/cdns3/core.h | 5 ++++-
drivers/usb/cdns3/drd.c | 16 ++++++++++++--
include/linux/pci_ids.h | 1 +
6 files changed, 73 insertions(+), 23 deletions(-)

diff --git a/drivers/usb/cdns3/cdns3-plat.c b/drivers/usb/cdns3/cdns3-plat.c
index 71c612e27b73..33746e672cda 100644
--- a/drivers/usb/cdns3/cdns3-plat.c
+++ b/drivers/usb/cdns3/cdns3-plat.c
@@ -75,6 +75,7 @@ static int cdns3_plat_probe(struct platform_device *pdev)
if (cdns->pdata && cdns->pdata->override_apb_timeout)
cdns->override_apb_timeout = cdns->pdata->override_apb_timeout;

+ cdns->no_drd = device_property_read_bool(dev, "no_drd");
platform_set_drvdata(pdev, cdns);

ret = platform_get_irq_byname(pdev, "host");
@@ -107,21 +108,23 @@ static int cdns3_plat_probe(struct platform_device *pdev)

cdns->dev_regs = regs;

- cdns->otg_irq = platform_get_irq_byname(pdev, "otg");
- if (cdns->otg_irq < 0)
- return dev_err_probe(dev, cdns->otg_irq,
- "Failed to get otg IRQ\n");
+ if (!cdns->no_drd) {
+ cdns->otg_irq = platform_get_irq_byname(pdev, "otg");
+ if (cdns->otg_irq < 0)
+ return dev_err_probe(dev, cdns->otg_irq,
+ "Failed to get otg IRQ\n");

- res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "otg");
- if (!res) {
- dev_err(dev, "couldn't get otg resource\n");
- return -ENXIO;
+ res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "otg");
+ if (!res) {
+ dev_err(dev, "couldn't get otg resource\n");
+ return -ENXIO;
+ }
+
+ cdns->otg_res = *res;
}

cdns->phyrst_a_enable = device_property_read_bool(dev, "cdns,phyrst-a-enable");

- cdns->otg_res = *res;
-
cdns->wakeup_irq = platform_get_irq_byname_optional(pdev, "wakeup");
if (cdns->wakeup_irq == -EPROBE_DEFER)
return cdns->wakeup_irq;
@@ -158,6 +161,7 @@ static int cdns3_plat_probe(struct platform_device *pdev)
goto err_cdns_init;

cdns->gadget_init = cdns3_plat_gadget_init;
+
ret = cdns_core_init_role(cdns);
if (ret)
goto err_cdns_init;
diff --git a/drivers/usb/cdns3/cdnsp-pci.c b/drivers/usb/cdns3/cdnsp-pci.c
index 432007cfe695..e20c59ceb8a4 100644
--- a/drivers/usb/cdns3/cdnsp-pci.c
+++ b/drivers/usb/cdns3/cdnsp-pci.c
@@ -19,6 +19,7 @@

struct cdnsp_wrap {
struct platform_device *plat_dev;
+ struct property_entry prop[3];
struct resource dev_res[6];
int devfn;
};
@@ -29,10 +30,15 @@ struct cdnsp_wrap {
#define RES_HOST_ID 3
#define RES_DEV_ID 4
#define RES_DRD_ID 5
-
+/* DRD PCI configuration - 64-bit addressing */
+/* First PCI function */
#define PCI_BAR_HOST 0
-#define PCI_BAR_OTG 0
#define PCI_BAR_DEV 2
+/* Second PCI function */
+#define PCI_BAR_OTG 0
+/* Device only PCI configuration - 32-bit addressing */
+/* First PCI function */
+#define PCI_BAR_ONLY_DEV 1

#define PCI_DEV_FN_HOST_DEVICE 0
#define PCI_DEV_FN_OTG 1
@@ -65,6 +71,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
struct cdnsp_wrap *wrap;
struct resource *res;
struct pci_dev *func;
+ bool no_drd = false;
int ret = 0;

/*
@@ -75,11 +82,14 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
pdev->devfn != PCI_DEV_FN_OTG))
return -EINVAL;

+ if (pdev->device == PCI_DEVICE_ID_CDNS_UDC_USBSSP)
+ no_drd = true;
+
func = cdnsp_get_second_fun(pdev);
- if (!func)
+ if (!func && !no_drd)
return -EINVAL;

- if (func->class == PCI_CLASS_SERIAL_USB_XHCI ||
+ if ((func && func->class == PCI_CLASS_SERIAL_USB_XHCI) ||
pdev->class == PCI_CLASS_SERIAL_USB_XHCI) {
ret = -EINVAL;
goto put_pci;
@@ -93,7 +103,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,

pci_set_master(pdev);

- if (pci_is_enabled(func)) {
+ if (func && pci_is_enabled(func)) {
wrap = pci_get_drvdata(func);
} else {
wrap = kzalloc_obj(*wrap);
@@ -106,10 +116,13 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
res = wrap->dev_res;

if (pdev->devfn == PCI_DEV_FN_HOST_DEVICE) {
+ int bar_dev = no_drd ? PCI_BAR_ONLY_DEV : PCI_BAR_DEV;
+
/* Function 0: host(BAR_0) + device(BAR_2). */
dev_dbg(&pdev->dev, "Initialize Device resources\n");
- res[RES_DEV_ID].start = pci_resource_start(pdev, PCI_BAR_DEV);
- res[RES_DEV_ID].end = pci_resource_end(pdev, PCI_BAR_DEV);
+
+ res[RES_DEV_ID].start = pci_resource_start(pdev, bar_dev);
+ res[RES_DEV_ID].end = pci_resource_end(pdev, bar_dev);
res[RES_DEV_ID].name = "dev";
res[RES_DEV_ID].flags = IORESOURCE_MEM;
dev_dbg(&pdev->dev, "USBSSP-DEV physical base addr: %pa\n",
@@ -145,9 +158,20 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
wrap->dev_res[RES_IRQ_OTG_ID].flags = IORESOURCE_IRQ;
}

- if (pci_is_enabled(func)) {
+ if (no_drd || pci_is_enabled(func)) {
+ u8 idx = 0;
+
/* set up platform device info */
pdata.override_apb_timeout = CHICKEN_APB_TIMEOUT_VALUE;
+ if (no_drd) {
+ wrap->prop[idx++] = PROPERTY_ENTRY_STRING("dr_mode", "peripheral");
+ wrap->prop[idx++] = PROPERTY_ENTRY_BOOL("no_drd");
+ } else {
+ wrap->prop[idx++] = PROPERTY_ENTRY_STRING("dr_mode", "otg");
+ wrap->prop[idx++] = PROPERTY_ENTRY_BOOL("usb-role-switch");
+ }
+
+ wrap->prop[idx] = (struct property_entry){ };
memset(&plat_info, 0, sizeof(plat_info));
plat_info.parent = &pdev->dev;
plat_info.fwnode = pdev->dev.fwnode;
@@ -158,6 +182,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
plat_info.dma_mask = pdev->dma_mask;
plat_info.data = &pdata;
plat_info.size_data = sizeof(pdata);
+ plat_info.properties = wrap->prop;
wrap->devfn = pdev->devfn;
/* register platform device */
wrap->plat_dev = platform_device_register_full(&plat_info);
@@ -185,13 +210,17 @@ static void cdnsp_pci_remove(struct pci_dev *pdev)
if (wrap->devfn == pdev->devfn)
platform_device_unregister(wrap->plat_dev);

- if (!pci_is_enabled(func))
+ if (!func || !pci_is_enabled(func))
kfree(wrap);

pci_dev_put(func);
}

static const struct pci_device_id cdnsp_pci_ids[] = {
+ { PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_UDC_USBSSP),
+ .class = PCI_CLASS_SERIAL_USB_DEVICE },
+ { PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_UDC_USBSSP),
+ .class = PCI_CLASS_SERIAL_USB_CDNS },
{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_USBSSP),
.class = PCI_CLASS_SERIAL_USB_DEVICE },
{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_USBSSP),
diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
index 10f00b6c3c83..72f7acba6258 100644
--- a/drivers/usb/cdns3/core.c
+++ b/drivers/usb/cdns3/core.c
@@ -71,7 +71,8 @@ static void cdns_role_stop(struct cdns *cdns)
static void cdns_exit_roles(struct cdns *cdns)
{
cdns_role_stop(cdns);
- cdns_drd_exit(cdns);
+ if (!cdns->no_drd)
+ cdns_drd_exit(cdns);
}

/**
diff --git a/drivers/usb/cdns3/core.h b/drivers/usb/cdns3/core.h
index dc8c4137de15..6abe231f4559 100644
--- a/drivers/usb/cdns3/core.h
+++ b/drivers/usb/cdns3/core.h
@@ -80,9 +80,11 @@ struct cdns3_platform_data {
* @pdata: platform data from glue layer
* @lock: spinlock structure
* @xhci_plat_data: xhci private data structure pointer
+ * @gadget_init: pointer to gadget initialization function
* @override_apb_timeout: hold value of APB timeout. For value 0 the default
* value in CHICKEN_BITS_3 will be preserved.
- * @gadget_init: pointer to gadget initialization function
+ * @no_drd: DRD register block is inaccessible - driver handles only
+ * device mode.
*/
struct cdns {
struct device *dev;
@@ -122,6 +124,7 @@ struct cdns {
struct xhci_plat_priv *xhci_plat_data;
int (*gadget_init)(struct cdns *cdns);
u32 override_apb_timeout;
+ bool no_drd;
};

int cdns_hw_role_switch(struct cdns *cdns);
diff --git a/drivers/usb/cdns3/drd.c b/drivers/usb/cdns3/drd.c
index 84fb38a5723a..38f3051c2188 100644
--- a/drivers/usb/cdns3/drd.c
+++ b/drivers/usb/cdns3/drd.c
@@ -107,7 +107,7 @@ void cdns_clear_vbus(struct cdns *cdns)
{
u32 reg;

- if (cdns->version != CDNSP_CONTROLLER_V2)
+ if (cdns->version != CDNSP_CONTROLLER_V2 || cdns->no_drd)
return;

reg = readl(&cdns->otg_cdnsp_regs->override);
@@ -120,7 +120,7 @@ void cdns_set_vbus(struct cdns *cdns)
{
u32 reg;

- if (cdns->version != CDNSP_CONTROLLER_V2)
+ if (cdns->version != CDNSP_CONTROLLER_V2 || cdns->no_drd)
return;

reg = readl(&cdns->otg_cdnsp_regs->override);
@@ -234,6 +234,9 @@ int cdns_drd_gadget_on(struct cdns *cdns)
u32 ready_bit;
int ret, val;

+ if (cdns->no_drd)
+ return 0;
+
/* switch OTG core */
writel(OTGCMD_DEV_BUS_REQ | reg, &cdns->otg_regs->cmd);

@@ -265,6 +268,9 @@ void cdns_drd_gadget_off(struct cdns *cdns)
{
u32 val;

+ if (cdns->no_drd)
+ return;
+
/*
* Driver should wait at least 10us after disabling Device
* before turning-off Device (DEV_BUS_DROP).
@@ -392,6 +398,12 @@ int cdns_drd_init(struct cdns *cdns)
u32 state, reg;
int ret;

+ if (cdns->no_drd) {
+ cdns->version = CDNSP_CONTROLLER_V2;
+ cdns->dr_mode = USB_DR_MODE_PERIPHERAL;
+ return 0;
+ }
+
regs = devm_ioremap_resource(cdns->dev, &cdns->otg_res);
if (IS_ERR(regs))
return PTR_ERR(regs);
diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
index 406abf629be2..a931fb201402 100644
--- a/include/linux/pci_ids.h
+++ b/include/linux/pci_ids.h
@@ -2424,6 +2424,7 @@
#define PCI_DEVICE_ID_CDNS_USBSS 0x0100
#define PCI_DEVICE_ID_CDNS_USB 0x0120
#define PCI_DEVICE_ID_CDNS_USBSSP 0x0200
+#define PCI_DEVICE_ID_CDNS_UDC_USBSSP 0x0400

#define PCI_VENDOR_ID_ARECA 0x17d3
#define PCI_DEVICE_ID_ARECA_1110 0x1110

---
base-commit: 5196f2c98340297e1fdd36555285e991ceddf776
change-id: 20260331-device_only-192d539430b5

Best regards,
--
Pawel Laszczak <pawell@cadence.com>