[PATCH 3/4] configs: Increase USB Hub debounce timeout in Agilex5

[Ravulapalli, Naresh Kumar]

On 08-Sep-25 6:32 PM, Marek Vasut wrote:
> 
> On 9/8/25 10:44 AM, Ravulapalli, Naresh Kumar wrote:
>> Hi Marek
>>
>> On 02-Sep-25 11:48 PM, Marek Vasut wrote:
>>> [CAUTION: This email is from outside your organization. Unless you
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>>>
>>> On 9/2/25 9:52 AM, Ravulapalli, Naresh Kumar wrote:
>>>>
>>>>
>>>> On 30-Aug-25 5:30 AM, Marek Vasut wrote:
>>>>>
>>>>> On 8/29/25 6:19 PM, Ravulapalli, Naresh Kumar wrote:
>>>>>> Hi Marek
>>>>>>
>>>>>> On 29-Aug-25 2:11 PM, Marek Vasut wrote:
>>>>>>>
>>>>>>> On 8/8/25 12:04 PM, Naresh Kumar Ravulapalli wrote:
>>>>>>>> Some USB devices need more time to be initialized. Hence,
>>>>>>>> increasing the default USB Hub debounce timeout value for
>>>>>>>> devices to be discovered, connected to Agilex5 boards.
>>>>>>> Is this really hub debounce timeout or usb_pgood_delay ?
>>>>>>>
>>>>>>> Which devices are those, include that in the commit message.
>>>>>>
>>>>>> Yes, timeout is related to USB connect/disconnect signal bounces not
>>>>>> about bus stability during init.
>>>>>>
>>>>>> Issue was mainly observed with legacy flash drives. Maybe I will
>>>>>> change
>>>>>> commit text from "Some USB devices need more time to be
>>>>>> initialized..."
>>>>>> to "Some old USB flash drives need more time to be initialized during
>>>>>> connect or disconnect events ..."?
>>>>>>
>>>>>> Note that I am not modifying the default Kconfig value in general;
>>>>>> change is only made for an SoCFPGA devkit we tested.
>>>>> Does this same issue go away if you set usb_pgood_delay to 2000 or
>>>>> higher too ?
>>>>
>>>> No, changing USB HUB debounce timeout is working for us.
>>> Look at this code:
>>>
>>> https://source.denx.de/u-boot/u-boot/-/blob/master/common/usb_hub.c?
>>> ref_type=heads#L199
>>>
>>> "
>>> #if CONFIG_IS_ENABLED(ENV_SUPPORT)
>>>         env = env_get("usb_pgood_delay");
>>>         if (env)
>>>                 pgood_delay = max(pgood_delay,
>>>                                   (unsigned)simple_strtol(env, NULL, 
>>> 0));
>>> #endif
>>>         debug("pgood_delay=%dms\n", pgood_delay);
>>>
>>>         /*
>>>          * Do a minimum delay of the larger value of 100ms or 
>>> pgood_delay
>>>          * so that the power can stablize before the devices are queried
>>>          */
>>>         hub->query_delay = get_timer(0) + max(100, (int)pgood_delay);
>>>
>>>         /*
>>>          * Record the power-on timeout here. The max. delay (timeout)
>>>          * will be done based on this value in the USB port loop in
>>>          * usb_hub_configure() later.
>>>          */
>>>         hub->connect_timeout = hub->query_delay + HUB_DEBOUNCE_TIMEOUT;
>>>         debug("devnum=%d poweron: query_delay=%d connect_timeout=%d\n",
>>>               dev->devnum, max(100, (int)pgood_delay),
>>>               max(100, (int)pgood_delay) + HUB_DEBOUNCE_TIMEOUT);
>>> "
>>>
>>> Changing both usb_pgood_delay or (CONFIG_USB_)HUB_DEBOUNCE_TIMEOUT
>>> should have the same effect. How come it does not ?
>>
>> CONFIG_USB_HUB_DEBOUNCE_TIMEOUT and pgood_delay are used for different
>> purposes. If I am not mistaken I think I explained this in my earlier
>> comments.
>>
>> Anyway, to further elaborate, CONFIG_USB_HUB_DEBOUNCE_TIMEOUT is used
>> for debounce timeouts during device connect events and pgood_delay is
>> used during initial VBus stabilization.
>>
>> You would be able to see this difference in the link below, where
>> pgood_delay which is populated into "hub->query_delay" is used for
>> voltages to stabilize before initiating communication and "hub-
>>  >connect_timeout" where "HUB_DEBOUNCE_TIMEOUT" is populated is used
>> after getting the port status.
>>
>> https://github.com/u-boot/u-boot/blob/328747974a0620d0996113fe2b3906b06e96de00/common/usb_hub.c#L455
>>
>> Also, the change made as part of the comment is not applicable to the
>> USB stack in general; it is only for our devkit defconfig.
> But none of this answers my question, looking at the aforementioned code
> -- Changing both usb_pgood_delay or (CONFIG_USB_)HUB_DEBOUNCE_TIMEOUT
> should have the same effect. How come it does not in your case ?

Maybe I wasn't explicit in my earlier comment, "No, changing USB HUB 
debounce timeout is working for us."

What I meant is I didn't want to modify usb_pgood_delay as my issue was 
with HUB_DEBOUNCE_TIMEOUT, so modifying this value worked for us.