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

Bjorn Helgaas
2026-03-31T18:12:10Z

On Tue, Mar 31, 2026 at 10:19:11AM +0200, Pawel Laszczak wrote:
> 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 +

Acked-by: Bjorn Helgaas <bhelgaas@google.com> # pci_ids.h

> 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>
>