linux-kernel - Re: [PATCH v2 0/3] Add the DWC3 instance name in traces

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Message-ID: <20260105161145.podzns57ekzjg3pj@synopsys.com>
Date: Mon, 5 Jan 2026 16:11:50 +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 v2 0/3] Add the DWC3 instance name in traces

Hi Greg,

On Mon, Jan 05, 2026, Greg Kroah-Hartman wrote:
> On Mon, Jan 05, 2026 at 05:23:22PM +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.
> > 
> > Hence append the controller base address into ftrace. This needs
> > the following reworks which is addressed using this patch series.
> > 
> >   1. Removal of dep->regs and use dwc->regs everywhere
> >   2. Use dwc pointer in all dwc3_readl/writel()
> >   3. Adding the base addr in traces.
> > 
> > Changes in v2:
> > - Avoid using macros for dwc3_readl/writel()
> > - Use base address intraces instead of dev name.
> 
> Wait, why change this?  The dev name is what you should care about.
> "base address" doesn't make much sense as this is on a lot of different
> busses, right?
> 

I asked Prashanth to do so. The reason is because the device name is not
consistent and not obvious for different busses. For example, for PCI
devices, the device name may be in a form of "dwc3.N.auto". If we only
have access to the traces and not the testing setup (which often is the
case), it's difficult to tell which is which. Also, very often the
consumer of the traces is also the hardware validation engineer, and
IMO, it's more understandable reading base address than device name.

BR,
Thinh