Re: [PATCH 08/15] xhci: dbc: serialize enabling and disabling dbc

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 6/15/26 09:11, Borah, Chaitanya Kumar wrote:
> 
> Hello Mathias,
> 
> On 6/3/2026 2:41 PM, Mathias Nyman wrote:
>> DbC can be enabled and disabled via sysfs, serialize those
>> with a mutex to make sure everything is done in the correct
>> order.
>>
>> remove xhci_do_dbc_stop() and integrate the register write and
>> dbc->state setting into xhci_do_stop()
>>
> 
> This patch seems to cause a regression in our CI. [1]
> 
> We could not revert the patch because of merge conflicts but resetting to the parent commit seems to heal the issue.
> 
> Could you please check why the patch causes this regression and provide
> a fix if necessary?

Ah, I see, deadlock when enabling DbC via sysfs on runtime suspended xhci

Appears this is an issue mid series in intel-next,
The last patch that enabled runtime pm for DbC should also fix this issue.

The DbC runtime pm support patch was dropped last minute from the upstream series.

I'll send it as a RFT, can you check it solve the issue in your CI

Details of deadlock issue while mid series:

dbc_store() {  // enable dbc via syfs
     mutex_lock(&dbc->enable_mutex);
     xhci_dbc_start(dbc);
         pm_runtime_get_sync(dbc->dev);
             xhci_dbc_resume()
                 mutex_lock(&dbc->enable_mutex);

Thanks
Mathias