From: Matthias Kaehlcke Subject: Re: [PATCH v8 3/3] Bluetooth: hci_qca: Disable IBS state machine and flush Tx buffer Date: Wed, 16 Jan 2019 15:08:01 -0800 Message-ID: <20190116230801.GT261387@google.com> References: <20190116114603.500-1-bgodavar@codeaurora.org> <20190116114603.500-4-bgodavar@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <20190116114603.500-4-bgodavar@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org To: Balakrishna Godavarthi Cc: marcel@holtmann.org, johan.hedberg@gmail.com, linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org, hemantg@codeaurora.org, linux-arm-msm@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org On Wed, Jan 16, 2019 at 05:16:03PM +0530, Balakrishna Godavarthi wrote: > During hci down we observed IBS sleep commands are queued in the Tx > buffer and hci_uart_write_work is sending data to the chip which is > not required as the chip is powered off. This patch will disable IBS > and flush the Tx buffer before we turn off the chip. > > Signed-off-by: Balakrishna Godavarthi > --- > drivers/bluetooth/hci_qca.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c > index 7e4afcf40da2..7330ba71ada4 100644 > --- a/drivers/bluetooth/hci_qca.c > +++ b/drivers/bluetooth/hci_qca.c > @@ -1275,6 +1275,14 @@ static const struct qca_vreg_data qca_soc_data = { > > static void qca_power_shutdown(struct hci_uart *hu) > { > + struct qca_data *qca = hu->priv; > + > + /* From this point we go into power off state. But serial port is > + * still open, stop queueing the IBS data and flush all the buffered > + * data in skb's. > + */ > + clear_bit(STATE_IN_BAND_SLEEP_ENABLED, &qca->flags); > + qca_flush(hu); > host_set_baudrate(hu, 2400); > qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE); > qca_power_setup(hu, false); Due to a race-condition there could be an IBS sleep command queued even after clearing the bit and flushing the queue. In qca_enqueue() we have this: static int qca_enqueue(struct hci_uart *hu, struct sk_buff *skb) { ... /* Don't go to sleep in middle of patch download or * Out-Of-Band(GPIOs control) sleep is selected. */ if (!test_bit(STATE_IN_BAND_SLEEP_ENABLED, &qca->flags)) { skb_queue_tail(&qca->txq, skb); return 0; } spin_lock_irqsave(&qca->hci_ibs_lock, flags); } With process X executing qca_power_shutdown() and process Y running qca_enqueue() this could happen: [X] test_bit(STATE_IN_BAND_SLEEP_ENABLED) => set [Y] clear_bit(STATE_IN_BAND_SLEEP_ENABLED) [Y] qca_flush(hu); [X] skb_queue_tail(&qca->txq, skb); The following should fix this race: --- a/drivers/bluetooth/hci_qca.c +++ b/drivers/bluetooth/hci_qca.c @@ -770,16 +770,17 @@ static int qca_enqueue(struct hci_uart *hu, struct sk_buff *skb) /* Prepend skb with frame type */ memcpy(skb_push(skb, 1), &hci_skb_pkt_type(skb), 1); + spin_lock_irqsave(&qca->hci_ibs_lock, flags); + /* Don't go to sleep in middle of patch download or * Out-Of-Band(GPIOs control) sleep is selected. */ if (!test_bit(STATE_IN_BAND_SLEEP_ENABLED, &qca->flags)) { skb_queue_tail(&qca->txq, skb); + spin_unlock_irqrestore(&qca->hci_ibs_lock, flags); return 0; } - spin_lock_irqsave(&qca->hci_ibs_lock, flags); - /* Act according to current state */ switch (qca->tx_ibs_state) { case HCI_IBS_TX_AWAKE: @@ -1275,13 +1276,17 @@ static const struct qca_vreg_data qca_soc_data = { static void qca_power_shutdown(struct hci_uart *hu) { struct qca_data *qca = hu->priv; + unsigned long flags; /* From this point we go into power off state. But serial port is * still open, stop queueing the IBS data and flush all the buffered * data in skb's. */ + spin_lock_irqsave(&qca->hci_ibs_lock, flags); clear_bit(STATE_IN_BAND_SLEEP_ENABLED, &qca->flags); qca_flush(hu); + spin_unlock_irqrestore(&qca->hci_ibs_lock, flags); + host_set_baudrate(hu, 2400); qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE); qca_power_setup(hu, false); Cheers Matthias