Re: [PATCH 1/1] xhci: dbc: support runtime suspend while DbC is in enabled state

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

On 6/16/26 12:46, Greg KH wrote:
> On Tue, Jun 16, 2026 at 11:09:32AM +0300, Mathias Nyman wrote:
>> Allow xHC to runtime suspend if DbC is in 'enabled' state for over
>> 15 seconds without a connect.
>>
>> Idea is that every time we go to 'enabled' state we make sure DbC runtime
>> pm usage is '1' and save a timestamp. if the event loop still finds DbC in
>> enabled state 15 seconds later then it decrease DbC runtime pm usage by
>> calling pm_runtime_put().
>> Enabled state is reached either when DbC is enabled by userspace or a
>> connected/configured DbC is disconnected.
>>
>> When a connect is detected we make sure DbC usage count is 1.
>>
>> If DbC has been in 'enabled' state for 15 seconds and DbC usage is
>> decreased to 0 by pm_runtime_put, then the whole xHC controller may
>> runtime suspends to PCI D3 state if no other devices are using it
>>
>> DbC sysfs file will show 'suspended' when xHC is suspended and will wake up
>> and enable DbC at cable connect, or when user writes 'enable' to the file.
>>
>> This patch was originally part of a larger DbC series, but dropped before
>> the series was submitted to 7.2-rc1. The series has a locking issue in
>> commit 520058b73ba3 ("xhci: dbc: serialize enabling and disabling dbc")
>> which is also resolved by this patch
>>
>> Fixes: 520058b73ba3 ("xhci: dbc: serialize enabling and disabling dbc")
>> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
>> ---
>>   .../testing/sysfs-bus-pci-drivers-xhci_hcd    |  2 +-
>>   drivers/usb/host/xhci-dbgcap.c                | 60 ++++++++++++++++++-
>>   drivers/usb/host/xhci-dbgcap.h                |  3 +
>>   3 files changed, 62 insertions(+), 3 deletions(-)
> 
> No "reported-by:"?

I'll send v2

-Mathias