Re: [PATCH v2 2/3] Bluetooth: hci_qca: Deassert RTS while baudrate change command

[Balakrishna Godavarthi]

Hi Matthias,

On 2018-11-27 01:12, Matthias Kaehlcke wrote:
> On Thu, Nov 22, 2018 at 05:45:11PM +0530, Balakrishna Godavarthi wrote:
> > This patch will help to stop frame reassembly errors while changing
> > the baudrate. This is because host send a change baudrate request
> > command to the chip with 115200 bps, Whereas chip will change their
> > UART clocks to the enable for new baudrate and sends the response
> > for the change request command with newer baudrate, On host side
> > we are still operating in 115200 bps which results of reading garbage
> > data. Here we are pulling RTS line, so that chip we will wait to send 
> > data
> > to host until host change its baudrate.
>
> Thanks for updating the commit message and provide more details!
>
> > Signed-off-by: Balakrishna Godavarthi <bgodavar@xxxxxxxxxxxxxx>
> > Tested-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> > ---
> > v2:
> >  * updated commit text and comments.
> > v1:
> >  * initial patch
> > ---
> >  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 f5dd323c1967..ed905ea1c58a 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;
> >
> > +		/* Deassert RTS while changing the baudrate of chip and host.
> > +		 * This will stop chip to transmit it response with an newer
> > +		 * baudrate until we change the baudarte.
>
> nit: baudrate
>
> re-nit (to consider if you respin anyway): 'This prevents the chip
> from transmitting its response with the new baudrate while the host
> port is still operating at the old speed'?
> (I'm not a native English speaker, probably there is still room for
> improvement ;-)

[Bala]: will update.

> Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>

--
Regards
Balakrishna.