[PATCH 1/3] usb: common: default dr_mode to OTG when not set

[Mattijs Korpershoek]

On Thu, Jan 15, 2026 at 10:17, Mattijs Korpershoek <mkorpershoek at kernel.org> wrote:

> Hi Casey,
>
> Thank you for the patch.
>
> On Wed, Jan 14, 2026 at 15:13, Casey Connolly <casey.connolly at linaro.org> wrote:
>
>> DT bindings dictate that dr_mode being unset on a DRD capable USB
>
> For the curious, this is defined in https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/usb/usb-drd.yaml#n23
>
>> controller means we should default to OTG mode. Adjust usb_get_dr_mode()
>> to reflect this.
>>
>> Signed-off-by: Casey Connolly <casey.connolly at linaro.org>
>> ---
>>  drivers/usb/common/common.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/common/common.c b/drivers/usb/common/common.c
>> index 13e9a61072a9..e3bd7339e68e 100644
>> --- a/drivers/usb/common/common.c
>> +++ b/drivers/usb/common/common.c
>> @@ -29,9 +29,10 @@ enum usb_dr_mode usb_get_dr_mode(ofnode node)
>>  
>>  	dr_mode = ofnode_read_string(node, "dr_mode");
>>  	if (!dr_mode) {
>>  		pr_debug("usb dr_mode not found\n");
>> -		return USB_DR_MODE_UNKNOWN;
>> +		/* Default to OTG mode as per DT bindings */
>
> Nitpick: can we change the comment to:
> /* Default to OTG mode as per devicetree/bindings/usb/usb-drd.yaml */
>
> This tells the same but is more precise and is imho, a more helpful
> comment.
>
> Reviewed-by: Mattijs Korpershoek <mkorpershoek at kernel.org>

Also, I just noticed, but there is another similar change here:
https://lore.kernel.org/all/20260108-usb-dwc3-exynos7870-v3-1-343fa1e81e48@disroot.org/

Casey, can you see if the above is useful to you?

>
>
>> +		return USB_DR_MODE_OTG;
>>  	}
>>  
>>  	for (i = 0; i < ARRAY_SIZE(usb_dr_modes); i++)
>>  		if (!strcmp(dr_mode, usb_dr_modes[i]))
>>
>> -- 
>> 2.51.0