Re: [PATCH v1 1/4] Bluetooth: hci_qca: use wait_until_sent() for power pulses

[Balakrishna Godavarthi]

Hi Johan,

On 2018-11-14 20:57, Johan Hovold wrote:
> On Tue, Nov 06, 2018 at 05:35:25PM +0530, Balakrishna Godavarthi wrote:
> > wcn3990 requires a power pulse to turn ON/OFF along with
> > regulators. Sometimes we are observing the power pulses are sent
> > out with some time delay, due to queuing these commands. This is
> > causing synchronization issues with chip, which intern delay the
> > chip setup or may end up with communication issues.
> >
> > Signed-off-by: Balakrishna Godavarthi <bgodavar@xxxxxxxxxxxxxx>
> > ---
> >  drivers/bluetooth/hci_qca.c | 22 +++++++++-------------
> >  1 file changed, 9 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> > index f72ded4ec9ae..051f081d1835 100644
> > --- a/drivers/bluetooth/hci_qca.c
> > +++ b/drivers/bluetooth/hci_qca.c
> > @@ -1016,8 +1016,7 @@ static inline void host_set_baudrate(struct 
> > hci_uart *hu, unsigned int speed)
> >  static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
> >  {
> >  	struct hci_uart *hu = hci_get_drvdata(hdev);
> > -	struct qca_data *qca = hu->priv;
> > -	struct sk_buff *skb;
> > +	int ret;
> >
> >  	/* These power pulses are single byte command which are sent
> >  	 * at required baudrate to wcn3990. On wcn3990, we have an external
> > @@ -1030,18 +1029,14 @@ static int qca_send_power_pulse(struct hci_dev 
> > *hdev, u8 cmd)
> >  	 * sending power pulses to SoC.
> >  	 */
> >  	bt_dev_dbg(hdev, "sending power pulse %02x to SoC", cmd);
> > -
> > -	skb = bt_skb_alloc(sizeof(cmd), GFP_KERNEL);
> > -	if (!skb)
> > -		return -ENOMEM;
> > -
> >  	hci_uart_set_flow_control(hu, true);
> > +	ret = serdev_device_write(hu->serdev, &cmd, sizeof(cmd), 0);
>
> Don't you want a non-zero timeout here? Otherwise you might as well 
> call
> serdev_device_write() directly.

[Bala]: we need an in definite timeout for these commands. will use 
HCI_UART_TX_WAKEUP.

> Also have you made sure that serdev_device_write_wakeup() is called in
> the drivers write-wakeup callback as serdev_device_write() requires?
>
> See this series in case what you really wanted was to wait indefinitely
> (you can use MAX_SCHEDULE_TIMEOUT):
>
> 	https://lkml.kernel.org/r/<20181114150904.19653-1-johan@xxxxxxxxxx>

[Bala]: thanks for pointers. from 
https://lore.kernel.org/patchwork/patch/1012358/
        it was clear to me that i need call below functions in order to 
wait until full data is sent.

        serdev_device_write_wakeup()
        serdev_device_write()
        serdev_device_wait_until_sent()

        correct me whether my understanding is correct.

> > +	if (ret < 0) {
> > +		bt_dev_err(hdev, "failed to send power pulse %02x to SoC", cmd);
> > +		return ret;
> > +	}
> >
> > -	skb_put_u8(skb, cmd);
> > -	hci_skb_pkt_type(skb) = HCI_COMMAND_PKT;
> > -
> > -	skb_queue_tail(&qca->txq, skb);
> > -	hci_uart_tx_wakeup(hu);
> > +	serdev_device_wait_until_sent(hu->serdev, 0);
> >
> >  	/* Wait for 100 uS for SoC to settle down */
> >  	usleep_range(100, 200);
> > @@ -1283,7 +1278,8 @@ static void qca_power_shutdown(struct hci_uart 
> > *hu)
> >
> >  	host_set_baudrate(hu, 2400);
> >  	hci_uart_set_flow_control(hu, true);
> > -	serdev_device_write_buf(serdev, &cmd, sizeof(cmd));
> > +	serdev_device_write(serdev, &cmd, sizeof(cmd), 0);
>
> Same here.
>
> > +	serdev_device_wait_until_sent(serdev, 0);
> >  	hci_uart_set_flow_control(hu, false);
> >  	qca_power_setup(hu, false);
> >  }
>
> Johan

--
Regards
Balakrishna.