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

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Message-ID: <2026010513-kinsman-moody-6d63@gregkh>
Date: Mon, 5 Jan 2026 20:59:04 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: Prashanth K <prashanth.k@....qualcomm.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

On Mon, Jan 05, 2026 at 05:01:00PM +0000, Thinh Nguyen wrote:
> On Mon, Jan 05, 2026, Greg Kroah-Hartman wrote:
> > On Mon, Jan 05, 2026 at 04:11:50PM +0000, Thinh Nguyen wrote:
> > > 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.
> > 
> > But all you need to know is "this is different than the other one", you
> > don't "need" the io address, right?  And if you really did, just add
> > that to the trace as well _when_ you actually need it.
> 
> The base address preserves that context to know which instance is which.
> If we have the base address, do we still need the device name?

If you have only the "base address", how do you know which device is which?

thanks,

greg k-h