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SubjectRe: [PATCH v1 2/4] Bluetooth: hci_qca: Pull RTS line high for baudrate change command
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@codeaurora.org>
>> ---
>> 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@chromium.org>

Thanks for testing.

--
Regards
Balakrishna.

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