xhci: dbc: support runtime suspend while DbC is in enabled state

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")
Reported-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Closes: https://lore.kernel.org/linux-usb/9ce24ff5-efab-4089-92d7-709862d68e6d@intel.com
Tested-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://patch.msgid.link/20260616100916.2234205-2-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions