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

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Message-ID: <20260115162234.ehm7l22ahh52d4y3@synopsys.com>
Date: Thu, 15 Jan 2026 16:22:58 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        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 v4 3/3] usb: dwc3: Log dwc3 address in traces

On Thu, Jan 15, 2026, Greg Kroah-Hartman wrote:
> On Wed, Jan 14, 2026 at 11:54:03PM +0000, Thinh Nguyen wrote:
> > On Wed, Jan 14, 2026, Thinh Nguyen wrote:
> > > On Wed, Jan 14, 2026, Greg Kroah-Hartman wrote:
> > > > On Wed, Jan 14, 2026 at 03:37:48PM +0530, Prashanth K wrote:
> > > > > + * @address: Cached lower 32-bit base address to be used for logging.
> > > > 
> > > > Why are 32bits enough / ok?  Why not use the full 64 that you really
> > > > have?  What happens if you have 2 devices with just the upper 32 bits
> > > > different?
> > > > 
> > > > This is a resource value, so why not use the proper type for it?
> > > > 
> > > 
> > > This is only intented to be used for logging, so I suggested to use u32.
> > > I want to avoid treating this struct member as a phys_addr_t where it
> > > may be misused.
> > > 
> > > As for the reason to capture only the lower 32-bit, it's just base on
> > > what I've seen so far. That I have not seen designs where the 2 or more
> > > instances are placed that far apart and share the same lower 32-bit.
> > > It's a bit nicer to shorten the address print at the start of a
> > > tracepoint. But if it's insufficient, there's no problem with using
> > > 64-bit.
> > > 
> > 
> > Or we can just remove this and print the address from
> > dwc->xhci_resources[0].start.
> 
> I thought I asked for that a few revisions ago :)

Ah, I missed that.

> 
> I'd prefer that, instead of saving off a value that you can look up if
> you need it.
> 

Yes, this is better.

Hi Prashanth, can we just use dwc->xhci_resources[0].start instead?

Thanks,
Thinh