Return-Path: From: Hans de Goede To: Marcel Holtmann , Gustavo Padovan , Johan Hedberg Cc: Hans de Goede , =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Danis?= , Lukas Wunner , linux-bluetooth@vger.kernel.org, linux-serial@vger.kernel.org, linux-acpi@vger.kernel.org Subject: [PATCH 4.16 REGRESSION fix 2/2] Bluetooth: hci_bcm: Set pulsed_host_wake flag in sleep parameters Date: Wed, 14 Mar 2018 23:06:03 +0100 Message-Id: <20180314220603.7559-3-hdegoede@redhat.com> In-Reply-To: <20180314220603.7559-1-hdegoede@redhat.com> References: <20180314220603.7559-1-hdegoede@redhat.com> List-ID: The IRQ output of the bcm bt-device is really a level IRQ signal, which signals a logical high as long as the device's buffer contains data. Since the draining in the buffer is done in the tty driver, we cannot (easily) wait in a threaded interrupt handler for the draining, after which the IRQ should go low again. So instead we treat the IRQ as an edge interrupt. This opens the window for a theoretical race where we wakeup, read some data and then autosuspend *before* the IRQ has gone (logical) low, followed by the device just at that moment receiving more data, causing the IRQ to stay high and we never see an edge. Since we call pm_runtime_mark_last_busy() on every received byte, there should be plenty time for the IRQ to go (logical) low before we ever suspend, so this should never happen, but after commit 43fff7683468 ("Bluetooth: hci_bcm: Streamline runtime PM code"), which has been reverted since, this was actually happening causing the device to get stuck in runtime suspend. The bcm bt-device actually has a workaround for this, if we set the pulsed_host_wake flag in the sleep parameters, then the device monitors if the host is draining the buffer and if not then after a timeout the device will pulse the IRQ line, causing us to see an edge, fixing the stuck in suspend condition. This commit sets the pulsed_host_wake flag to fix the (mostly theoretical) race caused by us treating the IRQ as an edge IRQ. Signed-off-by: Hans de Goede --- drivers/bluetooth/hci_bcm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/bluetooth/hci_bcm.c b/drivers/bluetooth/hci_bcm.c index b089012a49f9..04b9a6c75c75 100644 --- a/drivers/bluetooth/hci_bcm.c +++ b/drivers/bluetooth/hci_bcm.c @@ -307,7 +307,7 @@ static const struct bcm_set_sleep_mode default_sleep_params = { .usb_auto_sleep = 0, .usb_resume_timeout = 0, .break_to_host = 0, - .pulsed_host_wake = 0, + .pulsed_host_wake = 1, }; static int bcm_setup_sleep(struct hci_uart *hu) -- 2.14.3