Hi, On 1/28/21 12:58 AM, Abhishek Pandit-Subedi wrote: > Hi Hans, > > You can also implement hdev->prevent_wake to prevent configure wake > from running. Yes I did consider that, but there still is an issue sometimes on resume too and the BT_SUSPEND_DISCONNECT handling takes 200 ms which is nice to get rid of too. So I opted to just disable the hci_suspend_notifier(). > 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. The RTL8723bs is the cheapest of cheap wifi/bt combo chip and is often found on cheap/slow devices. I did see this: [ 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 At least once, it might just be that the 2 seconds elapsed before the reprobe ran (or there might still be a race somewhere). > 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. Ok, I did consider using a quirk for this myself, but I was not sure if this warranted a core change since this is a somewhat unique situation. I'll respin the patch into a patch-set adding a quirk, thank you for your feedback. Regards, Hans > 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 >> >
