Re: [PATCH v2 1/2] usb: dwc3-generic: set "mode" based on caller of dwc3_generic_probe()

[Roger Quadros <rogerq@kernel.org>]

Hi Siddharth,


On 03/12/2024 11:37, Siddharth Vadapalli wrote:
> There are only two callers of "dwc3_generic_probe()", namely:
> 1. dwc3_generic_peripheral_probe()
> 2. dwc3_generic_host_probe()
> Currently, the "mode" is set based on the device-tree node of the
> platform device. Also, the DWC3 core doesn't support updating the "mode"
> dynamically at runtime if it is set to "OTG", i.e. "OTG" is treated as a
> separate mode in itself, rather than being treated as a mode which should
> eventually lead to "host"/"peripheral".

Actually this is not entirely true. Sorry for not catching this earlier.
I did a deep dive today to debug why XHCI is being registered for both ports on am62.

I see that configs/am62x_a53_usbdfu.config is setting CONFIG_USB_XHCI_DWC3.
This is wrong. It should not be used for AM62x platform.

Also.

Please see dwc3_glue_bind_common().

        if (CONFIG_IS_ENABLED(DM_USB_GADGET) &&
            (dr_mode == USB_DR_MODE_PERIPHERAL || dr_mode == USB_DR_MODE_OTG)) {
                printf("%s: dr_mode: OTG or Peripheral\n", __func__);
                driver = "dwc3-generic-peripheral";
        } else if (CONFIG_IS_ENABLED(USB_HOST) && dr_mode == USB_DR_MODE_HOST) {
                printf("%s: dr_mode: HOST\n", __func__);
                driver = "dwc3-generic-host";
        } else {
                printf("%s: unsupported dr_mode %d\n", __func__, dr_mode);
                return -ENODEV;
        }

        ret = device_bind_driver_to_node(parent, driver, name,
                                         node, &dev);
        if (ret) {


So if dr_mode is "otg" it will be bound to dwc3-generic-peripheral driver only.
I verified that even if I change dr_mode from "peripheral" to "otg" DFU mode
does work from u-boot shell.

Which makes my suggestions for checking dr_mode during and your patch seem unnecessary.

What is not clear though is, why is DFU mode not working for you. At which stage
DFU is failing? R5 SPL/A53 SPL?

Can you please try disabling CONFIG_USB_XHCI_DWC3 in all configs as it will
hijack the controller exclusively for host mode.

> 
> Given that the callers of "dwc3_generic_probe()" clarify the expected
> "mode" of the USB Controller, use that "mode" instead of the one
> specified in the device-tree. This shall allow the USB Controller to
> function both as a "Host" and as a "Peripheral" when the "mode" is "otg"
> in the device-tree, based on the caller of "dwc3_generic_probe()".
> 
> Ideally, the USB ID pin should be used to determine whether or not the
> requested role can be enabled. However, that can be implemented in the
> future as an incremental feature over the current implementation.
> 
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
> ---
> 
> v1:
> https://patchwork.ozlabs.org/project/uboot/list/?series=434253&state=%2A&archive=both
> Changes since v1:
> - Based on the feedback received on the v1 series, the device-tree
>   specified role is also taken into account in dwc3_generic_probe(), in
>   addition to the caller of dwc3_generic_probe().
> 
>  drivers/usb/dwc3/dwc3-generic.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
> index 2ab41cbae45..fe98b50c42c 100644
> --- a/drivers/usb/dwc3/dwc3-generic.c
> +++ b/drivers/usb/dwc3/dwc3-generic.c
> @@ -51,7 +51,8 @@ struct dwc3_generic_host_priv {
>  };
>  
>  static int dwc3_generic_probe(struct udevice *dev,
> -			      struct dwc3_generic_priv *priv)
> +			      struct dwc3_generic_priv *priv,
> +			      enum usb_dr_mode mode)

This is not necessary as dwc3_generic_host_probe will only be
registered if dr_mode == "host" and dwc3_generic_peripheral_probe
will only be registered if dr_mode == "host" or "peripheral"

>  {
>  	int rc;
>  	struct dwc3_generic_plat *plat = dev_get_plat(dev);
> @@ -62,7 +63,19 @@ static int dwc3_generic_probe(struct udevice *dev,
>  
>  	dwc3->dev = dev;
>  	dwc3->maximum_speed = plat->maximum_speed;
> -	dwc3->dr_mode = plat->dr_mode;
> +
> +	/*
> +	 * If the controller supports OTG as indicated by plat->dr_mode,
> +	 * then either Host or Peripheral mode is acceptable.
> +	 * Otherwise, error out since the platform cannot support the mode
> +	 * being requested by the caller of dwc3_generic_probe().
> +	 */
> +	if (plat->dr_mode != mode && plat->dr_mode != USB_DR_MODE_OTG) {
> +		pr_err("Requested usb mode is not supported by platform\n");

This is actually not necessary. Sorry for suggesting this approach before.

> +		return -EINVAL;
> +	}
> +	dwc3->dr_mode = mode;
> +
>  #if CONFIG_IS_ENABLED(OF_CONTROL)
>  	dwc3_of_parse(dwc3);
>  
> @@ -197,7 +210,7 @@ static int dwc3_generic_peripheral_probe(struct udevice *dev)
>  {
>  	struct dwc3_generic_priv *priv = dev_get_priv(dev);
>  
> -	return dwc3_generic_probe(dev, priv);
> +	return dwc3_generic_probe(dev, priv, USB_DR_MODE_PERIPHERAL);
>  }
>  
>  static int dwc3_generic_peripheral_remove(struct udevice *dev)
> @@ -241,7 +254,7 @@ static int dwc3_generic_host_probe(struct udevice *dev)
>  	struct dwc3_generic_host_priv *priv = dev_get_priv(dev);
>  	int rc;
>  
> -	rc = dwc3_generic_probe(dev, &priv->gen_priv);
> +	rc = dwc3_generic_probe(dev, &priv->gen_priv, USB_DR_MODE_HOST);
>  	if (rc)
>  		return rc;
>  

-- 
cheers,
-roger