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

[Peter Chen <peter.chen@oss.qualcomm.com>]

On 26-07-17 01:56:59, Thinh Nguyen wrote:
> On Thu, Jul 16, 2026, Peter Chen wrote:
> > On 26-07-17 00:06:37, Thinh Nguyen wrote:
> > > > 
> > > > I have seen fewer platforms use "phy_type" at dts for arm64, dwc3
> > > > core uses it only for special cases and the code was added for
> > > > ten years ago. For the default situation, we may not need to
> > > > change DWC3_GUSB2PHYCFG_EUSB2OPMODE value for UTMI+, Thinh, is it
> > > > correct?
> > > > 
> > > 
> > > The GUSB2PHYCFG.eUSB2OPMODE is only relevant for host mode and mainly
> > > for electrical compliance. Usually by default, the CoreConsultant
> > > setting should have this set correctly. So not explicitly setting it
> > > should be functionally fine (IIRC).
> > > 
> > > That said, this is separate from the GUSB2PHYCFG.PHYIF, which the core
> > > uses dwc->hsphy_mode to indicate whether the UTMI interface is 8-bit or
> > > 16-bit.
> > > 
> > 
> > Why only rockchip uses this "phy_type" property, why other SoC vendors
> > no this requirement for UTMI width setting? 
> > 
> 
> Not just rockchip, some tegra and hikey also use it. Some old qcom dts
> files also have it for ulpi.

Tegra and old qcom platforms use chipidea, hikey uses dwc3.

> 
> It is typically set when the coreConsultant default differs from what
> the platform needs, so the driver can override it with the correct
> setting.
> 
> My point is that changing "phy_type" definition is more involved than it
> looks. I'm open to alternatives.
> 

I know your concern that in case the eUSB2 PHY SoC wants to change UTMI
width, it can't do that. Are there controller register know it connects
eUSB2 PHY?

For the place to put "eusb2" for phy type, I still think enum
usb_phy_interface at: include/linux/usb/phy.h is the most suitable
place, would you have any alternatives?

Another solution is using generic PHY API phy_get_mode, set fixed "eusb2"
mode at eUSB2 PHY driver, but it depends on PHY driver doesn't have
different settings for device and host mode.

Other solution is compare the generic PHY compatible string at dwc3 qcom
glue layer, it depends on eUSB2 PHY compatible string always contains
"eusb2-phy"

I prefer the solution that extend enum usb_phy_interface for eUSB2 PHY,
it uses existed kernel structure and device tree binding.

-- 

Thanks,
Peter Chen