Re: [PATCH] usb: dwc3: Support for USB3340x ULPI PHY, via "snps,enable_xcvrdly_quirk"

[Ingo Rohloff <ingo.rohloff@lauterbach.com>]

On Wed, 25 Feb 2026 00:05:17 +0000
Thinh Nguyen <Thinh.Nguyen@synopsys.com> wrote:

> > +	/*
> > +	 * Fixes High-speed negotiation issue with USB3340, see:
> > +	 * https://.../80000645A.pdf
> > +	 *    "Device Enumeration Failure with Link IP Systems"  
> 
> This platform specific info and how it was found should go into the
> commit message and not here.
>

Done.

> > +	 * According to documentation on the Internet,  
> 
> We should not just reference the "Internet". If you want to reference
> some documentation, please provide the DWC_usb3x document section and
> version.
>

I would love to, but Synopsys was completely unwilling to provide
a programming manual to me.

Synopsys told me I should contact Xilinx (now AMD) for access to the
programming manual; and of course Xilinx refused, because Xilinx
has signed an NDA.

The "Internet" was the only source, where I found this information.
The description I provide is from the forum post I now mention in the
commit message.
I put the description in the code, because I am afraid, that the forum
post vanishes and then this information is lost to the public.

I guess, if I were to gain access to the official programming manual,
citing it might be a violation of the NDA I likely would have signed,
but I am not a lawyer.

> 
> > +	 * DWC3_GUSB2PHYCFG_XCVRDLY:
> > +	 *    Adds a delay between the assertion of the
> > +	 *    ULPI Transceiver Select signal (for HS) and  
> 
> It can be for both ULPI and UTMI.
> 

Ah of course :-)
I now mention both: ULPI/UTMI.


> > +	dwc->enable_xcvrdly_quirk = device_property_read_bool(dev,
> > +				"snps,enable_xcvrdly_quirk");  
> 
> Use "-" instead of "_" for property name, and change it to
> "snps,enable-usb2-transceiver-delay"
> 
> ...
> > +	unsigned		enable_xcvrdly_quirk:1;  
> 
> Document the new field. Rename to enable_usb2_transceiver_delay.

Done.
Note: I used "-" before to avoid having different strings for the
member variable and the property name to make it easier to grep
for both at the same time.

> Also, how are you passing this quirk? Through devicetree or software
> node? I don't see the user of this property.
> 

On the hardware I have got (Xilinx Ultrascale+ ZynqMP) I pass it via
devicetree. I now added a 2nd commit, which adds documentation for the
devicetree bindings.

with best regards
  Ingo Rohloff

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Ingo ROHLOFF
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