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

Balakrishna Godavarthi
2018-11-27T06:41:13Z

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@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 ;-)

[Bala]: will update.

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

--
Regards
Balakrishna.