Re: [PATCH v3 1/2] usb: dwc3-generic: allow fallback of dr_mode property to "otg"

[Mattijs Korpershoek <mkorpershoek@kernel.org>]

On Fri, Jan 16, 2026 at 19:12, "Kaustabh Chakraborty" <kauschluss@disroot.org> wrote:

> On 2026-01-16 13:33 +01:00, Mattijs Korpershoek wrote:
>> Hi Kaustabh,
>>
>> Thank you for the patch.
>>
>> On Thu, Jan 08, 2026 at 18:03, Kaustabh Chakraborty <kauschluss@disroot.org> wrote:
>>
>>> Documentation [1] states that the default value of the dr_mode property
>>> is "otg". It also isn't marked a mandatory node, so it may or may not be
>>> set. So, accordingly if dr_mode is not mentioned in the devicetree node,
>>> OTG mode must be assumed.
>>>
>>> In this driver however, this case is not handled. If dr_mode is not
>>> mentioned, USB_DR_MODE_UNKNOWN is set. The logic implemented raises an
>>> error, instead of falling back to USB_DR_MODE_OTG. Correct this to
>>> conform to the specification.
>>>
>>> Link: https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/tree/Bindings/usb/usb-drd.yaml?h=v6.18-dts [1]
>>> Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
>>> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
>>
>> Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
>
> Thanks for your insight, but isn't this patch applied? This has been
> merged into u-boot/master already. But I don't see it in next.
> Confusing.

You are right. This patch was already applied. I usually check for an
email that states that the patch was applied but I forgot Marek usually
does not send those.
Sorry about that, I generated un-necessary noise.

It's normal that your patch has only be applied into u-boot/master.

Right now, we are in the U-Boot merge window. During this time, the next
branch is closed. All development and fixes go into master directly.

See:
https://docs.u-boot.org/en/latest/develop/release_cycle.html#current-status
https://docs.u-boot.org/en/latest/develop/process.html#management-summary

Hope that clears out the confusion.

>
>>
>> Note: there is a similar patch submitted by Casey here:
>> https://lore.kernel.org/all/20260114-casey-usb-role-switch-v1-1-fb7a626466b9@linaro.org/
>>
>> Can you have a look at that one please? You could review it or test it
>> to see if it works for you?
>
> This patch addresses a single point of failure, unlike mine.
>
>>
>> Thanks!
>> Mattijs
>>
>>> ---
>>>  drivers/usb/dwc3/dwc3-generic.c | 9 +++++++--
>>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
>>> index c09014aec60..c15eda19e8f 100644
>>> --- a/drivers/usb/dwc3/dwc3-generic.c
>>> +++ b/drivers/usb/dwc3/dwc3-generic.c
>>> @@ -10,6 +10,7 @@
>>>  #include <dm.h>
>>>  #include <reset.h>
>>>  #include <asm/gpio.h>
>>> +#include <dm/device_compat.h>
>>>  #include <dm/lists.h>
>>>  #include <linux/delay.h>
>>>  #include <linux/usb/gadget.h>
>>> @@ -173,8 +174,8 @@ static int dwc3_generic_of_to_plat(struct udevice *dev)
>>>  		node = dev_ofnode(dev->parent);
>>>  		plat->dr_mode = usb_get_dr_mode(node);
>>>  		if (plat->dr_mode == USB_DR_MODE_UNKNOWN) {
>>> -			pr_err("Invalid usb mode setup\n");
>>> -			return -ENODEV;
>>> +			dev_info(dev, "No USB mode specified. Using 'otg'\n");
>>> +			plat->dr_mode = USB_DR_MODE_OTG;
>>>  		}
>>>  	}
>>>  
>>> @@ -516,6 +517,10 @@ static int dwc3_glue_bind_common(struct udevice *parent, ofnode node)
>>>  	if (!dr_mode)
>>>  		dr_mode = usb_get_dr_mode(node);
>>>  
>>> +	/* usb mode must fallback to peripheral if not known */
>>> +	if (dr_mode == USB_DR_MODE_UNKNOWN)
>>> +		dr_mode = USB_DR_MODE_OTG;
>>> +
>>>  	if (CONFIG_IS_ENABLED(DM_USB_GADGET) &&
>>>  	    (dr_mode == USB_DR_MODE_PERIPHERAL || dr_mode == USB_DR_MODE_OTG)) {
>>>  		debug("%s: dr_mode: OTG or Peripheral\n", __func__);
>>>
>>> -- 
>>> 2.52.0