linux-kernel - Re: [PATCH v4 3/3] usb: dwc3: Log dwc3 address in traces

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Message-ID: <20260114223009.abnwgsnn2i36v3sf@synopsys.com>
Date: Wed, 14 Jan 2026 22:30:19 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: Prashanth K <prashanth.k@....qualcomm.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] usb: dwc3: Log dwc3 address in traces

On Wed, Jan 14, 2026, Greg Kroah-Hartman wrote:
> On Wed, Jan 14, 2026 at 03:37:48PM +0530, Prashanth K wrote:
> > When multiple DWC3 controllers are being used, trace events from
> > different instances get mixed up making debugging difficult as
> > there's no way to distinguish which instance generated the trace.
> > 
> > Use the register base address of dwc3 controller and append it to
> > trace events, so that the source instance is clearly identifiable.
> > 
> > Example trace output,
> > before ->  dwc3_event: event (00000101): Reset [U0]
> > after  ->  dwc3_event: 0a600000: event (00000101): Reset [U0]
> > 
> > Signed-off-by: Prashanth K <prashanth.k@....qualcomm.com>
> > ---
> >  drivers/usb/dwc3/core.c   |  5 ++-
> >  drivers/usb/dwc3/core.h   |  2 +
> >  drivers/usb/dwc3/ep0.c    |  2 +-
> >  drivers/usb/dwc3/gadget.c |  2 +-
> >  drivers/usb/dwc3/io.h     |  4 +-
> >  drivers/usb/dwc3/trace.h  | 88 ++++++++++++++++++++++++---------------
> >  6 files changed, 65 insertions(+), 38 deletions(-)
> > 
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index 670a9d4bfff2..125616489e04 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -158,7 +158,7 @@ void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode, bool ignore_susphy)
> >  	dwc3_writel(dwc, DWC3_GCTL, reg);
> >  
> >  	dwc->current_dr_role = mode;
> > -	trace_dwc3_set_prtcap(mode);
> > +	trace_dwc3_set_prtcap(dwc, mode);
> >  }
> >  EXPORT_SYMBOL_GPL(dwc3_set_prtcap);
> >  
> > @@ -2193,6 +2193,9 @@ int dwc3_core_probe(const struct dwc3_probe_data *data)
> >  	dwc_res = *res;
> >  	dwc_res.start += DWC3_GLOBALS_REGS_START;
> >  
> > +	/* Store the base register address for using it in traces later */
> > +	dwc->address = (u32)res->start;
> 
> And shouldn't this be dwc_res.start?  Why ignore
> DWC3_GLOBALS_REGS_START?

No. That's where the global registers start. The base address of dwc3
doesn't start at the global registers offset.

> 
> And because of that, shouldn't this go below:

No. See above.

> 
> > +
> >  	if (dev->of_node) {
> >  		struct device_node *parent = of_get_parent(dev->of_node);
> 
> That if statement, which will change the real resource start range
> value?
> 

BR,
Thinh