linux-kernel - Re: [PATCH v7 1/4] Bluetooth: hci_qca: use wait_until

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Message-ID: <20181228172005.GM261387@google.com>
Date:   Fri, 28 Dec 2018 09:20:05 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Balakrishna Godavarthi <bgodavar@...eaurora.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 v7 1/4] Bluetooth: hci_qca: use wait_until_sent() for
 power pulses

On Fri, Dec 28, 2018 at 05:18:16PM +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>
> ---
> Changes in v7:
>  *  updated the wait time to 5 ms after sending power pulses.
> 
> Changes in v6:
>  * added serdev_device_write_flush() in qca_send_power_pulse
>    instead during the power off pulse.
> 
> Changes in v5:
>  * added serdev_device_write_flush() in qca_power_off().
> ---
>  drivers/bluetooth/hci_qca.c | 43 ++++++++++++++++---------------------
>  1 file changed, 18 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index f036c8f98ea3..2aab34b3e696 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -1013,11 +1013,9 @@ static inline void host_set_baudrate(struct hci_uart *hu, unsigned int speed)
>  		hci_uart_set_baudrate(hu, speed);
>  }
>  
> -static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
> +static int qca_send_power_pulse(struct hci_uart *hu, 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
> @@ -1029,22 +1027,23 @@ static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
>  	 * save power. Disabling hardware flow control is mandatory while
>  	 * 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;
> +	bt_dev_dbg(hu->hdev, "sending power pulse %02x to controller", cmd);
>  
> +	serdev_device_write_flush(hu->serdev);
>  	hci_uart_set_flow_control(hu, true);
> +	ret = serdev_device_write_buf(hu->serdev, &cmd, sizeof(cmd));
> +	if (ret < 0) {
> +		bt_dev_err(hu->hdev, "failed to send power pulse %02x", 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);
> +	/* Wait of 5ms is required for assuring to send the byte on the Tx
> +	 * line and also for the controller to settle down for the received
> +	 * byte.
> +	 */
> +	usleep_range(5000, 6000);

We could be more flexible with the range, e.g. 5 to 10 ms, but it's
also fine as is.

>  	hci_uart_set_flow_control(hu, false);
>  
>  	return 0;
> @@ -1116,7 +1115,6 @@ static int qca_set_speed(struct hci_uart *hu, enum qca_speed_type speed_type)
>  
>  static int qca_wcn3990_init(struct hci_uart *hu)
>  {
> -	struct hci_dev *hdev = hu->hdev;
>  	struct qca_serdev *qcadev;
>  	int ret;
>  
> @@ -1139,12 +1137,12 @@ static int qca_wcn3990_init(struct hci_uart *hu)
>  
>  	/* Forcefully enable wcn3990 to enter in to boot mode. */
>  	host_set_baudrate(hu, 2400);
> -	ret = qca_send_power_pulse(hdev, QCA_WCN3990_POWEROFF_PULSE);
> +	ret = qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
>  	if (ret)
>  		return ret;
>  
>  	qca_set_speed(hu, QCA_INIT_SPEED);
> -	ret = qca_send_power_pulse(hdev, QCA_WCN3990_POWERON_PULSE);
> +	ret = qca_send_power_pulse(hu, QCA_WCN3990_POWERON_PULSE);
>  	if (ret)
>  		return ret;
>  
> @@ -1274,13 +1272,8 @@ static const struct qca_vreg_data qca_soc_data = {
>  
>  static void qca_power_shutdown(struct hci_uart *hu)
>  {
> -	struct serdev_device *serdev = hu->serdev;
> -	unsigned char cmd = QCA_WCN3990_POWEROFF_PULSE;
> -
>  	host_set_baudrate(hu, 2400);
> -	hci_uart_set_flow_control(hu, true);
> -	serdev_device_write_buf(serdev, &cmd, sizeof(cmd));
> -	hci_uart_set_flow_control(hu, false);
> +	qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
>  	qca_power_setup(hu, false);
>  }
>  

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