Re: [PATCH v8 1/3] Bluetooth: hci_qca: use wait_until_sent() for power pulses

[Balakrishna Godavarthi]

Hi Matthias,

On 2019-01-17 01:52, Matthias Kaehlcke wrote:
> On Wed, Jan 16, 2019 at 05:16:01PM +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>
> > ---
> > Changes in v8:
> >  * Updated 1 second timeout instead of indefinite wait.
> >
> > Changes in v7:
> >  *  updated the wait time to 5 ms after sending power pulses.
> >
> > Changes in v6:
> >  * added serdev_device_write_flush() in qca_send_power_pulse
> >    instead during the power off pulse.
> >
> > Changes in v5:
> >  * added serdev_device_write_flush() in qca_power_off().
> > ---
> >  drivers/bluetooth/hci_qca.c | 46 
> > ++++++++++++++++---------------------
> >  1 file changed, 20 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> > index f036c8f98ea3..681bfa30467e 100644
> > --- a/drivers/bluetooth/hci_qca.c
> > +++ b/drivers/bluetooth/hci_qca.c
> > @@ -60,6 +60,7 @@
> >  #define IBS_WAKE_RETRANS_TIMEOUT_MS	100
> >  #define IBS_TX_IDLE_TIMEOUT_MS		2000
> >  #define BAUDRATE_SETTLE_TIMEOUT_MS	300
> > +#define POWER_PULSE_TRANS_TIMEOUT_MS	1000
>
> nit: Not that it should make a different in normal operation, but 1s
> seems extreme. Is there really any chance that the byte hasn't been
> sent after say 100ms (which is still an eternity for a single byte)?
[Bala]: i missed to address this. for now let us have 1 second delay.
        based on stress test or further enchantments we can reduce this 
delay.

> >  /* susclk rate */
> >  #define SUSCLK_RATE_32KHZ	32768
> > @@ -1013,11 +1014,10 @@ static inline void host_set_baudrate(struct 
> > hci_uart *hu, unsigned int speed)
> >  		hci_uart_set_baudrate(hu, speed);
> >  }
> >
> > -static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
> > +static int qca_send_power_pulse(struct hci_uart *hu, u8 cmd)
> >  {
> > -	struct hci_uart *hu = hci_get_drvdata(hdev);
> > -	struct qca_data *qca = hu->priv;
> > -	struct sk_buff *skb;
> > +	int ret;
> > +	int timeout = __msecs_to_jiffies(POWER_PULSE_TRANS_TIMEOUT_MS);
>
> use msecs_to_jiffies()
>
> >  	/* These power pulses are single byte command which are sent
> >  	 * at required baudrate to wcn3990. On wcn3990, we have an external
> > @@ -1029,22 +1029,22 @@ static int qca_send_power_pulse(struct hci_dev 
> > *hdev, u8 cmd)
> >  	 * save power. Disabling hardware flow control is mandatory while
> >  	 * 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;
> > +	bt_dev_dbg(hu->hdev, "sending power pulse %02x to controller", cmd);
> >
> > +	serdev_device_write_flush(hu->serdev);
> >  	hci_uart_set_flow_control(hu, true);
> > +	ret = serdev_device_write_buf(hu->serdev, &cmd, sizeof(cmd));
> > +	if (ret < 0) {
> > +		bt_dev_err(hu->hdev, "failed to send power pulse %02x", 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);
> > -
> > -	/* Wait for 100 uS for SoC to settle down */
> > -	usleep_range(100, 200);
> > +	serdev_device_wait_until_sent(hu->serdev, timeout);
> > +	/* Wait of 5ms is required for assuring to send the byte on the Tx
> > +	 * line and also for the controller to settle down for the received
> > +	 * byte.
> > +	 */
> > +	usleep_range(5000, 6000);
>
> I incorrectly claimed that there might be still bytes sitting in the
> UART FIFO when serdev_device_wait_until_sent() returns, Johan
> corrected me on that (thanks!). So if it takes the SoC 100us to settle
> down we should be good with the original code.
>
> Cheers
>
> Matthias

--
Regards
Balakrishna.