Re: [PATCH v1 2/4] Bluetooth: hci_qca: Pull RTS line high for baudrate change command

[Balakrishna Godavarthi]

Hi Matthias,

On 2018-11-14 07:25, Matthias Kaehlcke wrote:
> On Tue, Nov 06, 2018 at 05:35:26PM +0530, Balakrishna Godavarthi wrote:
> > This patch will pull the RTS line high instead of turning off the
> > flow control, while changing baudrate of host and chip.
>
> Please don't only describe what is changed, but also why this change
> is necessary.
>
> IIUC the BT chip honors flow control during baudrate changes, however
> it sometimes sends 'garbage' which results in "Bluetooth: hci0: Frame
> reassembly failed (-84)" messages.

[Bala]: will update the commit text.

> > Signed-off-by: Balakrishna Godavarthi <bgodavar@xxxxxxxxxxxxxx>
> > ---
> >  drivers/bluetooth/hci_qca.c | 23 ++++++++++++-----------
> >  1 file changed, 12 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> > index 051f081d1835..8301663f0004 100644
> > --- a/drivers/bluetooth/hci_qca.c
> > +++ b/drivers/bluetooth/hci_qca.c
> > @@ -963,7 +963,6 @@ static int qca_set_baudrate(struct hci_dev *hdev, 
> > uint8_t baudrate)
> >  	struct hci_uart *hu = hci_get_drvdata(hdev);
> >  	struct qca_data *qca = hu->priv;
> >  	struct sk_buff *skb;
> > -	struct qca_serdev *qcadev;
> >  	u8 cmd[] = { 0x01, 0x48, 0xFC, 0x01, 0x00 };
> >
> >  	if (baudrate > QCA_BAUDRATE_3200000)
> > @@ -977,13 +976,6 @@ static int qca_set_baudrate(struct hci_dev *hdev, 
> > uint8_t baudrate)
> >  		return -ENOMEM;
> >  	}
> >
> > -	/* Disabling hardware flow control is mandatory while
> > -	 * sending change baudrate request to wcn3990 SoC.
> > -	 */
> > -	qcadev = serdev_device_get_drvdata(hu->serdev);
> > -	if (qcadev->btsoc_type == QCA_WCN3990)
> > -		hci_uart_set_flow_control(hu, true);
> > -
> >  	/* Assign commands to change baudrate and packet type. */
> >  	skb_put_data(skb, cmd, sizeof(cmd));
> >  	hci_skb_pkt_type(skb) = HCI_COMMAND_PKT;
> > @@ -999,9 +991,6 @@ static int qca_set_baudrate(struct hci_dev *hdev, 
> > uint8_t baudrate)
> >  	schedule_timeout(msecs_to_jiffies(BAUDRATE_SETTLE_TIMEOUT_MS));
> >  	set_current_state(TASK_RUNNING);
> >
> > -	if (qcadev->btsoc_type == QCA_WCN3990)
> > -		hci_uart_set_flow_control(hu, false);
> > -
> >  	return 0;
> >  }
> >
> > @@ -1086,6 +1075,7 @@ static int qca_check_speeds(struct hci_uart *hu)
> >  static int qca_set_speed(struct hci_uart *hu, enum qca_speed_type 
> > speed_type)
> >  {
> >  	unsigned int speed, qca_baudrate;
> > +	struct qca_serdev *qcadev;
> >  	int ret;
> >
> >  	if (speed_type == QCA_INIT_SPEED) {
> > @@ -1097,6 +1087,14 @@ static int qca_set_speed(struct hci_uart *hu, 
> > enum qca_speed_type speed_type)
> >  		if (!speed)
> >  			return 0;
> >
> > +		/* Pulling RTS line to high is mandatory while sending change
> > +		 * baudrate request to SoC and also while setting the host
> > +		 * baudrate.
> > +		 */
>
> Instead of just stating that this is 'mandatory' explain why it is
> needed. Also better say 'Deassert RTS' instead of the more lower level
> 'Pulling RTS line to high'. It could be something like 'Deassert RTS
> to prevent the BT controller from sending garbage during the baudrate
> change.'

[Bala]: will update the comment.

> > +		qcadev = serdev_device_get_drvdata(hu->serdev);
> > +		if (qcadev->btsoc_type == QCA_WCN3990)
> > +			serdev_device_set_rts(hu->serdev, false);
> > +
> >  		qca_baudrate = qca_get_baudrate_value(speed);
> >  		bt_dev_dbg(hu->hdev, "Set UART speed to %d", speed);
> >  		ret = qca_set_baudrate(hu->hdev, qca_baudrate);
> > @@ -1104,6 +1102,9 @@ static int qca_set_speed(struct hci_uart *hu, 
> > enum qca_speed_type speed_type)
> >  			return ret;
> >
> >  		host_set_baudrate(hu, speed);
> > +
> > +		if (qcadev->btsoc_type == QCA_WCN3990)
> > +			serdev_device_set_rts(hu->serdev, true);
> >  	}
> >
> >  	return 0;
>
> Tested-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>

Thanks for testing.

--
Regards
Balakrishna.