Re: [PATCH] usb: dwc3: Use the correct PHY mode for USB3 PHY

[Prashanth K <prashanth.k@oss.qualcomm.com>]

On 11/4/2026 5:42 AM, Thinh Nguyen wrote:
> Hi,
> 
> On Mon, Oct 12, 2026, Prashanth K wrote:
>> DWC3 currently configures USB3 PHYs with PHY_MODE_USB_HOST when
>> switching the controller to host mode. Even though usb_add_hcd()
>> sets the flag corrrectly, it gets overwritten in DWC3 layer.
>>
>> Some PHY drivers distinguish between USB2 and SS host modes and
>> expect USB3 PHYs to be configured with PHY_MODE_USB_HOST_SS. Using
>> PHY_MODE_USB_HOST may result in incorrect PHY programming. Fix this
>> by using PHY_MODE_USB_HOST_SS for USB3 PHYs.
>>
>> Signed-off-by: Prashanth K <prashanth.k@oss.qualcomm.com>
>> ---
>>  drivers/usb/dwc3/core.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index fd5c2cd36c59..1bb87a370725 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -251,7 +251,7 @@ static void __dwc3_set_mode(struct work_struct *work)
>>  			for (i = 0; i < dwc->num_usb2_ports; i++)
>>  				phy_set_mode(dwc->usb2_generic_phy[i], PHY_MODE_USB_HOST);
>>  			for (i = 0; i < dwc->num_usb3_ports; i++)
>> -				phy_set_mode(dwc->usb3_generic_phy[i], PHY_MODE_USB_HOST);
>> +				phy_set_mode(dwc->usb3_generic_phy[i], PHY_MODE_USB_HOST_SS);
>>  
>>  			if (dwc->dis_split_quirk) {
>>  				reg = dwc3_readl(dwc, DWC3_GUCTL3);
>> @@ -1643,7 +1643,7 @@ static int dwc3_core_init_mode(struct dwc3 *dwc)
>>  		for (i = 0; i < dwc->num_usb2_ports; i++)
>>  			phy_set_mode(dwc->usb2_generic_phy[i], PHY_MODE_USB_HOST);
>>  		for (i = 0; i < dwc->num_usb3_ports; i++)
>> -			phy_set_mode(dwc->usb3_generic_phy[i], PHY_MODE_USB_HOST);
>> +			phy_set_mode(dwc->usb3_generic_phy[i], PHY_MODE_USB_HOST_SS);
>>  
>>  		ret = dwc3_host_init(dwc);
>>  		if (ret)
>> -- 
>> 2.34.1
>>
> 
> Can you take a look at Sashiko's review comments? I think the points
> raised there are valid and should be addressed:
> 
> https://lore.kernel.org/linux-usb/sashiko-outbox-167906@kernel.org/

Yes, I was thinking to add a vendor hook for qcom and modify it from
there, so that other phy drivers wont be affected, will come up with a V2.

Thanks,
Prashanth K