linux-kernel - Re: [PATCH v1 1/4] Bluetooth: hci_qca: use wait_until

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Date:   Thu, 15 Nov 2018 20:04:29 +0530
From:   Balakrishna Godavarthi <bgodavar@...eaurora.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     marcel@...tmann.org, johan.hedberg@...il.com, mka@...omium.org,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        hemantg@...eaurora.org, linux-arm-msm@...r.kernel.org,
        Johan Hovold <jhovold@...il.com>
Subject: Re: [PATCH v1 1/4] Bluetooth: hci_qca: use wait_until_sent() for
 power pulses

Hi Johan,

On 2018-11-14 20:57, Johan Hovold wrote:
> On Tue, Nov 06, 2018 at 05:35:25PM +0530, Balakrishna Godavarthi wrote:
>> wcn3990 requires a power pulse to turn ON/OFF along with
>> regulators. Sometimes we are observing the power pulses are sent
>> out with some time delay, due to queuing these commands. This is
>> causing synchronization issues with chip, which intern delay the
>> chip setup or may end up with communication issues.
>> 
>> Signed-off-by: Balakrishna Godavarthi <bgodavar@...eaurora.org>
>> ---
>>  drivers/bluetooth/hci_qca.c | 22 +++++++++-------------
>>  1 file changed, 9 insertions(+), 13 deletions(-)
>> 
>> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
>> index f72ded4ec9ae..051f081d1835 100644
>> --- a/drivers/bluetooth/hci_qca.c
>> +++ b/drivers/bluetooth/hci_qca.c
>> @@ -1016,8 +1016,7 @@ static inline void host_set_baudrate(struct 
>> hci_uart *hu, unsigned int speed)
>>  static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
>>  {
>>  	struct hci_uart *hu = hci_get_drvdata(hdev);
>> -	struct qca_data *qca = hu->priv;
>> -	struct sk_buff *skb;
>> +	int ret;
>> 
>>  	/* These power pulses are single byte command which are sent
>>  	 * at required baudrate to wcn3990. On wcn3990, we have an external
>> @@ -1030,18 +1029,14 @@ static int qca_send_power_pulse(struct hci_dev 
>> *hdev, u8 cmd)
>>  	 * sending power pulses to SoC.
>>  	 */
>>  	bt_dev_dbg(hdev, "sending power pulse %02x to SoC", cmd);
>> -
>> -	skb = bt_skb_alloc(sizeof(cmd), GFP_KERNEL);
>> -	if (!skb)
>> -		return -ENOMEM;
>> -
>>  	hci_uart_set_flow_control(hu, true);
>> +	ret = serdev_device_write(hu->serdev, &cmd, sizeof(cmd), 0);
> 
> Don't you want a non-zero timeout here? Otherwise you might as well 
> call
> serdev_device_write() directly.
> 

[Bala]: we need an in definite timeout for these commands. will use 
HCI_UART_TX_WAKEUP.

> Also have you made sure that serdev_device_write_wakeup() is called in
> the drivers write-wakeup callback as serdev_device_write() requires?
> 
> See this series in case what you really wanted was to wait indefinitely
> (you can use MAX_SCHEDULE_TIMEOUT):
> 
> 	https://lkml.kernel.org/r/<20181114150904.19653-1-johan@...nel.org>
> 

[Bala]: thanks for pointers. from 
https://lore.kernel.org/patchwork/patch/1012358/
         it was clear to me that i need call below functions in order to 
wait until full data is sent.

         serdev_device_write_wakeup()
         serdev_device_write()
         serdev_device_wait_until_sent()

         correct me whether my understanding is correct.

>> +	if (ret < 0) {
>> +		bt_dev_err(hdev, "failed to send power pulse %02x to SoC", cmd);
>> +		return ret;
>> +	}
>> 
>> -	skb_put_u8(skb, cmd);
>> -	hci_skb_pkt_type(skb) = HCI_COMMAND_PKT;
>> -
>> -	skb_queue_tail(&qca->txq, skb);
>> -	hci_uart_tx_wakeup(hu);
>> +	serdev_device_wait_until_sent(hu->serdev, 0);
>> 
>>  	/* Wait for 100 uS for SoC to settle down */
>>  	usleep_range(100, 200);
>> @@ -1283,7 +1278,8 @@ static void qca_power_shutdown(struct hci_uart 
>> *hu)
>> 
>>  	host_set_baudrate(hu, 2400);
>>  	hci_uart_set_flow_control(hu, true);
>> -	serdev_device_write_buf(serdev, &cmd, sizeof(cmd));
>> +	serdev_device_write(serdev, &cmd, sizeof(cmd), 0);
> 
> Same here.
> 
>> +	serdev_device_wait_until_sent(serdev, 0);
>>  	hci_uart_set_flow_control(hu, false);
>>  	qca_power_setup(hu, false);
>>  }
> 
> Johan

-- 
Regards
Balakrishna.