Re: [PATCH v4 1/2] dt-bindings: qcom,snps-dwc3: Add property indicating presence of eUSB2 phy

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Mon, Jul 13, 2026, Peter Chen wrote:
> On 26-07-13 23:41:14, Thinh Nguyen wrote:
> > On Mon, Jul 13, 2026, Peter Chen wrote:
> > > On 26-07-13 08:26:59, Krzysztof Kozlowski wrote:
> > > > >> And Dmitry already said this at v3.
> > > > > 
> > > > > And I've already responded to his comment in v3:
> > > > > https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/ahjYwJtiMsm0BcCh@vbox/__;!!A4F2R9G_pg!YksJ0tPtRth9ez8t0GB_WaxH3ynx3ya8M8aFIyKfYpApRC_79Ig93CqE2MKcrGJ6O6t_Dl3RD1zftrnxhdtcfoW7hgep8w$ 
> > > > 
> > > > It does not change the fact that type of phy is implied by compatible,
> > > > thus you do not get a new property.
> > > > 
> > > > 
> > > 
> > > For USB2 PHY, it has property "phy_type" already, it could extend support
> > > list to eUSB2 like below, dwc3 qcom glue layer could call of_usb_get_phy_mode
> > > or re-use dwc3->hsphy_mode depends on where it needs to use.
> > > 
> > > diff --git a/drivers/usb/phy/of.c b/drivers/usb/phy/of.c
> > > index 1ab134f45d67..5cbf17d493ad 100644
> > > --- a/drivers/usb/phy/of.c
> > > +++ b/drivers/usb/phy/of.c
> > > @@ -16,6 +16,7 @@ static const char *const usbphy_modes[] = {
> > >  	[USBPHY_INTERFACE_MODE_ULPI]	= "ulpi",
> > >  	[USBPHY_INTERFACE_MODE_SERIAL]	= "serial",
> > >  	[USBPHY_INTERFACE_MODE_HSIC]	= "hsic",
> > > +	[USBPHY_INTERFACE_MODE_EUSB2]	= "eusb2",
> > >  };
> > > 
> > > 
> > 
> > eusb2 uses utmi, so it doesn't fit here as a separate mode.
> > 
> 
> Hi Thinh
> 
> Yes, eUSB2 is based on UTMI Parallel mode, but it has dedicated
> Physical Layer Supplement [1], eg at CH2.4, it lists eUSB2 PHY
> Features.
> 
> 
> > To go this route properly, we'd need to introduce a new phy type
> > attribute in the phy framework, which will be a bigger change that may
> > impact more than this driver.
> > 
> 
> It is not at generic PHY framework, it is just for USB PHY dedicated.
> 
> I do not see big changes, it only needs to change above files and related
> dt-binding files, and other users may leverage it if the controller
> has special sequence or settings for eUSB2.
> 

The usbphy_modes describes the interface between the controller and the
phy. eusb2 still uses utmi, so adding eusb2 there is sematically
incorrect. If we introduce the eusb2 mode there, we'd have to audit dwc3
and every other driver that uses usbphy_modes to handle the new mode
correctly.

That said, I have no objection to adding a new phy type for eusb2. I
just want to note it is a bigger change relative to adding a boolean
property to the DT binding.

Thanks,
Thinh