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

[Ravulapalli, Naresh Kumar]

Hi Marek

On 02-Sep-25 11:48 PM, Marek Vasut wrote:
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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/altera-innersource/applications.fpga.soc.uboot-socfpga-dev/blob/b3772135cc63737dbe8e1180a2f8c0e2645590aa/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.

Kind Regards
Naresh