[Bug 200039] BT advertising packet wakes up the system from S3 and suspend-to-idle

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https://bugzilla.kernel.org/show_bug.cgi?id=200039

--- Comment #23 from Raghuram Hegde (raghuram.hegde@intel.com) ---
(In reply to AceLan Kao from comment #22)
> I think the behavior should be normal.
> When BT dialog is opened, it start accepting all advertisement, and stop
> receiving packet after it's closed. This behavior is easy to be observed.
> From the full log, packets before #219 are received when the BT dialog is
> opened, and #220 is received during S3.
> 
> But the issue is, the advertising packets are only be received after there
> is a paired BT4 device(no matter it's connected or not).
> It very simple to verify.
> 
> 1. remove all BT devices from BT dialog and close the BT dialog
> 2. run "btmon" and got nothing
> 
> 1. pair non-BT4 devices(you can leave it connected) and close BT dialog
> 2. nothing from "btmon" if you don't touch the paired device.
> 
> 1. pair BT4 devices and disconnected them(even power off them)
> 2. we got advertising packet from other BT4 devices.
> 
> I'm not sure if "Accept all advertisement" is the culprit, but I'm willing
> to know if there is any command we can try to disable it to see if it helps.


In the full log, you can see that after #123, MGMT command 'Add Device' is sent
with Action parameter set to 'Auto-connect remote device (0x02)'. So, when
pairing with a LE device, 'HCI_AUTO_CONN_ALWAYS' flag is set.

In the HCI Disconnection Complete Event handler (hci_disconn_complete_evt in
net/bluetooth/hci_event.c), you can see that if the 'HCI_AUTO_CONN_ALWAYS' flag
is set, LE passive scan will be started.

Since for a paired LE device, 'HCI_AUTO_CONN_ALWAYS' flag is set, when we
disconnect it, LE passive scan will be started.

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