linux-kernel - Re: [PATCH v2 3/3] Bluetooth: hci_qca: Fix frame reassembly errors for wcn3990

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Message-ID: <20181127000950.GY22824@google.com>
Date:   Mon, 26 Nov 2018 16:09:50 -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 v2 3/3] Bluetooth: hci_qca: Fix frame reassembly errors
 for wcn3990

On Thu, Nov 22, 2018 at 05:45:12PM +0530, Balakrishna Godavarthi wrote:
> During initalization of wcn3990, we observed UART is reading some
> stray bytes on the Rx line. This is logging Frame reassembly errors
> on the serial console. This could be because of tristate of Tx line
> of wcn3990 during boot up.
> 
> [  176.929612] Bluetooth: hci_qca.c:qca_recv() hci0: Frame reassembly failed (-84)
> [  176.945734] Bluetooth: hci_qca.c:qca_recv() hci0: Frame reassembly failed (-84)
> [  176.953298] Bluetooth: hci_qca.c:qca_recv() hci0: Frame reassembly failed (-84)
> [  177.010660] Bluetooth: hci_qca.c:qca_recv() hci0: Frame reassembly failed (-84)
> [  177.067633] Bluetooth: hci_qca.c:qca_recv() hci0: Frame reassembly failed (-84)
> 
> Now we enable a flag during bootup to stop executing proto receive
> function and clear it back once the initialization is done.
> 
> Signed-off-by: Balakrishna Godavarthi <bgodavar@...eaurora.org>
> Tested-by: Matthias Kaehlcke <mka@...omium.org>
> ---
> v2:
>  * Updated commit text & comments.
> v1: 
>  * initial patch
> ---
>  drivers/bluetooth/hci_qca.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index ed905ea1c58a..2f3d9e16ba5a 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -56,6 +56,7 @@
>  
>  /* Controller states */
>  #define STATE_IN_BAND_SLEEP_ENABLED	1
> +#define STATE_DISCARD_RX		2
>  
>  #define IBS_WAKE_RETRANS_TIMEOUT_MS	100
>  #define IBS_TX_IDLE_TIMEOUT_MS		2000
> @@ -511,6 +512,7 @@ static int qca_open(struct hci_uart *hu)
>  		} else {
>  			hu->init_speed = qcadev->init_speed;
>  			hu->oper_speed = qcadev->oper_speed;
> +			set_bit(STATE_DISCARD_RX, &qca->flags);
>  			ret = qca_power_setup(hu, true);
>  			if (ret) {
>  				destroy_workqueue(qca->workqueue);
> @@ -903,6 +905,13 @@ static int qca_recv(struct hci_uart *hu, const void *data, int count)
>  	if (!test_bit(HCI_UART_REGISTERED, &hu->flags))
>  		return -EUNATCH;
>  
> +	/* We discard Rx data received while device is in booting
> +	 * stage, This is because of BT chip Tx line is in tristate.
> +	 * Due to this we read some garbage data on UART Rx.
> +	 */
> +	if (test_bit(STATE_DISCARD_RX, &qca->flags))
> +		return 0;
> +
>  	qca->rx_skb = h4_recv_buf(hu->hdev, qca->rx_skb, data, count,
>  				  qca_recv_pkts, ARRAY_SIZE(qca_recv_pkts));
>  	if (IS_ERR(qca->rx_skb)) {
> @@ -1193,6 +1202,7 @@ static int qca_setup(struct hci_uart *hu)
>  		if (ret)
>  			return ret;
>  
> +		clear_bit(STATE_DISCARD_RX, &qca->flags);
>  		ret = qca_read_soc_version(hdev, &soc_ver);
>  		if (ret)
>  			return ret;
> @@ -1269,6 +1279,14 @@ static const struct qca_vreg_data qca_soc_data = {
>  
>  static void qca_power_shutdown(struct hci_uart *hu)
>  {
> +	struct qca_data *qca = hu->priv;
> +
> +	/* From this point we go into power off state,
> +	 * disable IBS and discard all the queued data.
> +	 */
> +	clear_bit(STATE_IN_BAND_SLEEP_ENABLED, &qca->flags);

Is IBS actually related to the frame reassembly errors or is this
addressing a different issue? In 100 iteratios of 'hciconfig up/down'
without clearing the flag I didn't observe any frame reassembly
errors.

> +	set_bit(STATE_DISCARD_RX, &qca->flags);
> +	qca_flush(hu);
>  	host_set_baudrate(hu, 2400);
>  	qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
>  	qca_power_setup(hu, false);