linux-kernel - Re: [PATCH v1 4/4] Bluetooth: hci_qca: Fix frame reassembly errors for wcn3990

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Date:   Wed, 14 Nov 2018 11:36:20 -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 v1 4/4] Bluetooth: hci_qca: Fix frame reassembly errors
 for wcn3990

On Tue, Nov 06, 2018 at 05:35:28PM +0530, Balakrishna Godavarthi wrote:
> [  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)
> 
> The above errors log on console due to receiving of stray bytes
> when wcn3990 boot up's i.e. when during initial setup procedure.

Please shortly introduce the topic instead of starting with the log
messages.

> Signed-off-by: Balakrishna Godavarthi <bgodavar@...eaurora.org>
> ---
>  drivers/bluetooth/hci_qca.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index 97b57e0f4725..341f80606574 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 due multiple baudrate switch is causing
> +	 * UART to read some garbage data.
> +	 */

This isn't entirely correct. I saw frame reassembly errors before
qca_wcn3990_init() is called, i.e. no baudrate changes. Some of the
garbage seems to be sent shortly after powering on the controller.

> +	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)) {
> @@ -1192,10 +1201,12 @@ static int qca_setup(struct hci_uart *hu)
>  		set_bit(HCI_QUIRK_USE_BDADDR_PROPERTY, &hdev->quirks);
>  		clear_bit(HCI_QUIRK_RESET_ON_CLOSE, &hdev->quirks);
>  		hu->hdev->shutdown = qca_power_off;
> +
>  		ret = qca_wcn3990_init(hu);
>  		if (ret)
>  			return ret;
>  
> +		clear_bit(STATE_DISCARD_RX, &qca->flags);
>  		ret = qca_read_soc_version(hdev, &soc_ver);
>  		if (ret)
>  			return ret;
> @@ -1278,8 +1289,15 @@ 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);
> +	/* 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);
> +	set_bit(STATE_DISCARD_RX, &qca->flags);
> +	qca_flush(hu);
> +
>  	hci_uart_set_flow_control(hu, true);
> +	host_set_baudrate(hu, 2400);
>  	serdev_device_write(serdev, &cmd, sizeof(cmd), 0);
>  	serdev_device_wait_until_sent(serdev, 0);
>  	hci_uart_set_flow_control(hu, false);

This change won't win a beauty price, but it seems it is needed to
suppress the 'frame reassembly' spam, unless the controller can be
convinced to stop sending garbage in the first place.

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