Re: [PATCH] usb: dwc3: Log dwc3 instance name in traces

[Prashanth K <prashanth.k@oss.qualcomm.com>]

On 9/5/2025 5:14 AM, Thinh Nguyen wrote:
> On Thu, Sep 04, 2025, Prashanth K wrote:
>>
>>
>> On 9/4/2025 5:30 AM, Thinh Nguyen wrote:
>>> On Wed, Sep 03, 2025, Prashanth K wrote:
>>>>
>>>>
>>>> On 9/3/2025 5:14 AM, Thinh Nguyen wrote:
>>>>> On Mon, Sep 01, 2025, Prashanth K wrote:
>>>>>>
>>>>>>
>>>>>> On 8/29/2025 4:18 AM, Thinh Nguyen wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> On Mon, Aug 25, 2025, 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 device name to trace events to clearly identify the
>>>>>>>> source instance.
>>>>>>>
>>>>>>> Can we print the base address instead of the device name? This will be
>>>>>>> consistent across different device names, and it will be easier to
>>>>>>> create filter.
>>>>>>>
>>>>>> Did you mean to print the iomem (base address) directly?
>>>>>> I think using device name is more readable, in most cases device name
>>>>>> would contain the base address also. Let me know if you are pointing to
>>>>>> something else.>>
>>>>>
>>>>> Yes, I mean the device base address. PCI devices won't have the base
>>>>> address as part of the device name.
>>>>>
>>>> But the base address (void __iomem *base) wouldn't be helpful.
>>>> Using the base address, i guess we would be able to differentiate the
>>>> traces when there are multiple instances, but it wouldn't help us
>>>> identify which controller instance generated which trace.
>>>>
>>>> And for PCI devices, i agree that it doesn't have  address in device
>>>> name, but i think we should be able to identify the correct instance
>>>> based on the bus/device numbers, right ?
>>>>
>>>
>>> We may not have the PCI domain numbers if it's a child device as in the
>>> case of dwc3-pci or dwc3-haps.
>>>
>>> The base address _does_ tell you exactly which device the tracepoints
>>> correspond to. The device name is inconsistent between different device
>>> types and only relevant if we have access to the system to know which
>>> name belongs to which instance.
>>
>> Yes, I agree that device name would be inconsistent for different for
>> PCI (and HAPS) devices. But IMO using base address (virtual) would just
>> make it more harder to read and identify the instance.
>>
>> Perhaps we can cache the register addr and use it, what do you think?
>> Here we can at least differentiate the instances based on HW addr.
>>
>> snprintf(dwc->inst, sizeof(dwc->inst), "0x%08llx", (unsigned long
>> long)res->start);
>> dev_info(dwc->dev, "addr:%s\n", dwc->inst);
>>
>> Output --> [    4.521746] dwc3 a600000.usb: addr:0x0a600000
> 
> I think there's some misunderstanding here. I refer the base address as
> the hardware address.
> 
> I prefer something like this:
> 
>     dwc3_event: 0a600000: event (00000101): Reset [U0]
> 
> instead of the device name like this:
> 
>    dwc3_event: a600000.usb: event (00000101): Reset [U0]
> 
> BR,
> Thinh

Initially I was also talking about HW address, but since we were
discussing this under dwc3_readl/writel functions context, i also got
confused whether you are pointing out the HW address or virtual address.

Anyways, i guess the above method using snprintf on res->start is one
way to get base address, is there any way to do this?

Regards,
Prashanth K