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

Matthias Kaehlcke
2018-11-26T19:42:15Z

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@codeaurora.org>
> Tested-by: Matthias Kaehlcke <mka@chromium.org>
> ---
> 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 ;-)

Reviewed-by: Matthias Kaehlcke <mka@chromium.org>