linux-kernel - Re: [PATCH v2 3/3] usb: dwc3: Log dwc3 instance name in traces

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Message-ID: <2026010652-dissuade-reproduce-008d@gregkh>
Date: Tue, 6 Jan 2026 10:58:10 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Prashanth K <prashanth.k@....qualcomm.com>
Cc: Thinh Nguyen <Thinh.Nguyen@...opsys.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] usb: dwc3: Log dwc3 instance name in traces

On Mon, Jan 05, 2026 at 05:23:25PM +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.
> 
> Append the base address of dwc3 controller 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   |  6 ++-
>  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, 66 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 670a9d4bfff2..3aa85f5f1c47 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 +2193,10 @@ int dwc3_core_probe(const struct dwc3_probe_data *data)
>  	dwc_res = *res;
>  	dwc_res.start += DWC3_GLOBALS_REGS_START;
>  
> +	/* Store the physical base address for logging in trace */
> +	snprintf(dwc->base_addr, sizeof(dwc->base_addr), "%08llx",
> +		 (unsigned long long)res->start);

I think start is defined as resource_size_t, which is really
phys_addr_t, which is then either a u64 or u32, so why not just use u64
here?

And are you _sure_ it is ok to expose that to userspace?


> +
>  	if (dev->of_node) {
>  		struct device_node *parent = of_get_parent(dev->of_node);
>  
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index 23188b910528..c16e47273ea0 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1178,6 +1178,7 @@ struct dwc3_glue_ops {
>   * @wakeup_pending_funcs: Indicates whether any interface has requested for
>   *			 function wakeup in bitmap format where bit position
>   *			 represents interface_id.
> + * @base_addr: The HW base address of DWC3 controller.

You already have this pointer to the resource in dwc3 somewhere, so why
are you storing this as a char string and not just always using the
"real" resource instead?

And also, document this as ONLY needed for debugging things, that's not
obvious here at all.

thanks,

greg k-h