linux-kernel - Re: [PATCH v3 1/4] Bluetooth: hci_qca: use wait_until

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Date:   Wed, 5 Dec 2018 07:25:03 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Balakrishna Godavarthi <bgodavar@...eaurora.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
Subject: Re: [PATCH v3 1/4] Bluetooth: hci_qca: use wait_until_sent() for
 power pulses

On Fri, Nov 30, 2018 at 08:32:44PM +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>
> ---
> v3:
>   * no change.
> v2: 
>   * Updated function qca_send_power_pulse()
>   * addressed reviewer comments.

Please make sure to include reviewers on CC when resending, and as
someone else already mentioned, be a bit more specific about what
changes you actually made in response to the review feedback you
received.

> v1:
>  * initial patch
> ---
>  drivers/bluetooth/hci_qca.c | 37 +++++++++++++------------------------
>  1 file changed, 13 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index f036c8f98ea3..f5dd323c1967 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
> @@ -1029,19 +1027,16 @@ 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 SoC", cmd);
>  	hci_uart_set_flow_control(hu, true);
> +	ret = serdev_device_write(hu->serdev, &cmd, sizeof(cmd), 0);

You're still using 0 as a timeout here which is broken, as I already
told you.

>From 4.21 this will result in an indefinite timeout, but currently
implies not to wait for a full write buffer to drain at all.

As I also mentioned, you need to to make sure to call
serdev_device_write_wakeup() in the write_wakup() path if you are going
to use serdev_device_write() at all.

Johan