Hi Hans, You can also implement hdev->prevent_wake to prevent configure wake from running. hci_unregister_dev will also clear any tasks during resume, unregister the pm notifier and cancel the suspend work so if reprobe takes <2s (default suspend work timeout), you shouldn't see a delay or any errors. I'm not 100% confident that the reprobe worker and the pm notifier won't race so I'm ok with this change as well. I would prefer if the driver only set a quirk and the actual register/unregister was handled entirely inside hci_core though. Thanks, Abhishek On Wed, Jan 27, 2021 at 1:58 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > The hci_suspend_notifier which was introduced last year, is causing > problems for uart attached btrtl devices. These devices may loose their > firmware and their baudrate setting over a suspend/resume. > > Since we don't even know the baudrate after a suspend/resume recovering > from this is tricky. The driver solves this by treating these devices > the same as USB BT HCIs which drop of the bus during suspend. > > Specifically the driver: > 1. Simply unconditionally turns the device fully off during > system-suspend to save maximum power. > 2. Calls device_reprobe() from a workqueue to fully re-init the device > from scratch on system-resume (unregistering the old HCI and > registering a new HCI). > > This means that these devices do not benefit from the suspend / resume > handling work done by the hci_suspend_notifier. At best this unnecessarily > adds some time to the suspend/resume time. > > But in practice this is actually causing problems: > > 1. These btrtl devices seem to not like the HCI_OP_WRITE_SCAN_ENABLE( > SCAN_DISABLED) request being send to them when entering the > BT_SUSPEND_CONFIGURE_WAKE state. The same request send on > BT_SUSPEND_DISCONNECT works fine, but the second one send (unnecessarily?) > from the BT_SUSPEND_CONFIGURE_WAKE transition causes the device to hang: > > [ 573.497754] PM: suspend entry (s2idle) > [ 573.554615] Filesystems sync: 0.056 seconds > [ 575.837753] Bluetooth: hci0: Timed out waiting for suspend events > [ 575.837801] Bluetooth: hci0: Suspend timeout bit: 4 > [ 575.837925] Bluetooth: hci0: Suspend notifier action (3) failed: -110 > > 2. The PM_POST_SUSPEND / BT_RUNNING transition races with the > driver-unbinding done by the device_reprobe() work. > If the hci_suspend_notifier wins the race it is talking to a dead > device leading to the following errors being logged: > > [ 598.686060] Bluetooth: hci0: Timed out waiting for suspend events > [ 598.686124] Bluetooth: hci0: Suspend timeout bit: 5 > [ 598.686237] Bluetooth: hci0: Suspend notifier action (4) failed: -110 > > In both cases things still work, but the suspend-notifier is causing > these ugly errors getting logged and ut increase both the suspend- and > the resume-time by 2 seconds. > > This commit works around these problems by disabling (unregistering) > the hci_suspend_notifier. > > Note that any eventual hci_unregister_dev() will call > unregister_pm_notifier() a second time, this is fine it will > simply fail with -ENOENT and hci_unregister_dev() ignores the > return value. > > Cc: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx> > Cc: Vasily Khoruzhick <anarsoul@xxxxxxxxx> > Cc: Abhishek Pandit-Subedi <abhishekpandit@xxxxxxxxxxxx> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > --- > drivers/bluetooth/hci_h5.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/bluetooth/hci_h5.c b/drivers/bluetooth/hci_h5.c > index 7be16a7f653b..acbcc676d6c2 100644 > --- a/drivers/bluetooth/hci_h5.c > +++ b/drivers/bluetooth/hci_h5.c > @@ -14,6 +14,7 @@ > #include <linux/of_device.h> > #include <linux/serdev.h> > #include <linux/skbuff.h> > +#include <linux/suspend.h> > > #include <net/bluetooth/bluetooth.h> > #include <net/bluetooth/hci_core.h> > @@ -876,6 +877,13 @@ static int h5_btrtl_setup(struct h5 *h5) > bool flow_control; > int err; > > + /* > + * Since h5_btrtl_resume() does a device_reprobe() the suspend handling > + * done by the hci_suspend_notifier is not necessary; it actually causes > + * delays and a bunch of errors to get logged, so disable it. > + */ > + unregister_pm_notifier(&h5->hu->hdev->suspend_notifier); > + > btrtl_dev = btrtl_initialize(h5->hu->hdev, h5->id); > if (IS_ERR(btrtl_dev)) > return PTR_ERR(btrtl_dev); > -- > 2.29.2 >
