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

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Date:   Tue, 27 Nov 2018 12:11:08 +0530
From:   Balakrishna Godavarthi <bgodavar@...eaurora.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     marcel@...tmann.org, johan.hedberg@...il.com,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        hemantg@...eaurora.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 2/3] Bluetooth: hci_qca: Deassert RTS while baudrate
 change command

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@...eaurora.org>
>> Tested-by: Matthias Kaehlcke <mka@...omium.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@...omium.org>

-- 
Regards
Balakrishna.