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SubjectRe: [PATCH v8 3/3] Bluetooth: hci_qca: Disable IBS state machine and flush Tx buffer
On 2019-01-17 04:38, Matthias Kaehlcke wrote:
> 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 <bgodavar@codeaurora.org>
>> ---
>> 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);
> +
[Bala]: Thanks for catch this. yes you are rite, we will have an byte
queued in the skb.
will update with the lock.

> host_set_baudrate(hu, 2400);
> qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
> qca_power_setup(hu, false);
>
> Cheers
>
> Matthias

--
Regards
Balakrishna.

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