Re: [PATCH v9 1/3] Bluetooth: hci_qca: use wait_until_sent() for power pulses

Balakrishna Godavarthi <bgodavar@xxxxxxxxxxxxxx> · Tue, 29 Jan 2019 18:38:12 +0530

Hi Matthias,

On 2019-01-28 23:17, Matthias Kaehlcke wrote:
On Mon, Jan 28, 2019 at 07:19:56PM +0530, Balakrishna Godavarthi wrote:
Hi Matthias,

On 2019-01-25 06:44, Matthias Kaehlcke wrote:
> On Thu, Jan 24, 2019 at 05:38:06PM +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 v9:
> >  * Reverted to 100us sleep.
> >  * used inline call msecs_to_jiffies()
> >
> > 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 | 40
> > +++++++++++++++----------------------
> >  1 file changed, 16 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> > index f036c8f98ea3..c08f4d105e73 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
>
> I still doubt that this mega-timeout of 1s is needed, but it shouldn't
> do any harm either, so whatever ...
>

[Bala]: for now let us have it. we can improve it in the improvement 
patch
        based on the results.

Fine.

With the UART buffer flushed and flow control disabled I wonder though
what makes you think that it could take longer than a few milliseconds
for the byte being put on the wire, short of a bug in the UART driver
or hardware, which (if it existed) shouldn't be worked around here.

[Bala]: i don't see any issue decreasing to milliseconds. will update it 
to 100ms.

> >  /* 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);
> >
> >  	/* These power pulses are single byte command which are sent
> >  	 * at required baudrate to wcn3990. On wcn3990, we have an external
> > @@ -1029,21 +1029,19 @@ 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);
> > +	serdev_device_wait_until_sent(hu->serdev, timeout);
> >
> > -	/* Wait for 100 uS for SoC to settle down */
> > +	/* Wait for 100 uS for SoC to settle down for the received byte. */
>
> I don't think 'for the received byte' adds much value here. If you
> respin anyway I'd suggest to leave the comment as is.
>

[Bala]: will update.

> >  	usleep_range(100, 200);
> >  	hci_uart_set_flow_control(hu, false);
> >
> > @@ -1116,7 +1114,6 @@ static int qca_set_speed(struct hci_uart *hu,
> > enum qca_speed_type speed_type)
> >
> >  static int qca_wcn3990_init(struct hci_uart *hu)
> >  {
> > -	struct hci_dev *hdev = hu->hdev;
> >  	struct qca_serdev *qcadev;
> >  	int ret;
> >
> > @@ -1139,12 +1136,12 @@ static int qca_wcn3990_init(struct hci_uart
> > *hu)
> >
> >  	/* Forcefully enable wcn3990 to enter in to boot mode. */
> >  	host_set_baudrate(hu, 2400);
> > -	ret = qca_send_power_pulse(hdev, QCA_WCN3990_POWEROFF_PULSE);
> > +	ret = qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
> >  	if (ret)
> >  		return ret;
> >
> >  	qca_set_speed(hu, QCA_INIT_SPEED);
> > -	ret = qca_send_power_pulse(hdev, QCA_WCN3990_POWERON_PULSE);
> > +	ret = qca_send_power_pulse(hu, QCA_WCN3990_POWERON_PULSE);
> >  	if (ret)
> >  		return ret;
> >
> > @@ -1274,13 +1271,8 @@ static const struct qca_vreg_data
> > qca_soc_data = {
> >
> >  static void qca_power_shutdown(struct hci_uart *hu)
> >  {
> > -	struct serdev_device *serdev = hu->serdev;
> > -	unsigned char cmd = QCA_WCN3990_POWEROFF_PULSE;
> > -
> >  	host_set_baudrate(hu, 2400);
> > -	hci_uart_set_flow_control(hu, true);
> > -	serdev_device_write_buf(serdev, &cmd, sizeof(cmd));
> > -	hci_uart_set_flow_control(hu, false);
> > +	qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
> >  	qca_power_setup(hu, false);
> >  }
> >
>
> Looks good to me besides possible minor improvements:
>
> Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>

--
Regards
Balakrishna.