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Date:   Tue, 12 Mar 2019 12:36:37 -0700
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>
Cc:     linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org,
        Balakrishna Godavarthi <bgodavar@codeaurora.org>,
        Hemantg <hemantg@codeaurora.org>
Subject: Re: [PATCH 2/2] Bluetooth: hci_qca: wcn3990: Drop baudrate change
 vendor event
Message-ID: <20190312193637.GE200579@google.com>
References: <20190307004041.38059-1-mka@chromium.org>
 <20190307004041.38059-3-mka@chromium.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi,

I held back with sending an updated version because I observe baudrate
changes to fail with a 'frame reassembly' error in about 1 out of 500
cases. After some debugging I'm fairly confident the error is not
caused by this change.

For the record:

This is the data that is received received in response to the read
version and the change baudrate commands when the baudrate change
is (completely) succesful:

04 ff 0e 00 02 0a 00 00 00 01 00 01 02 14 02 01
40 04 0e 04 01 00 00 00 04 ff 02 92 01 04 0e 04
01 00 00 00

Which translates to the following frames:

# vendor event with the version info
04 ff 0e 00 02 0a 00 00 00 01 00 01 02 14 02 01 40

# command complete event (with opcode 0)
04 0e 04 01 00 00 00

# vendor event confirming the baudrate change
04 ff 02 92 01

# command complete event (with opcode 0)
04 0e 04 01 00 00 00


When the frame reassembly error occurs we receive:

04 ff 0e 00 02 0a 00 00 00 01 00 01 02 14 02 01
40 04 0e 04 04 ff 02 92 01 04 0e 04 01 00 00 00

or:

# vendor event with the version info
04 ff 0e 00 02 0a 00 00 00 01 00 01 02 14 02 01 40

# first bytes (!) of a command complete event
04 0e 04

# vendor event confirming the baudrate change
04 ff 02 92 01

# command complete event (with opcode 0)
04 0e 04 01 00 00 00


The data was logged at UART level, hence the HCI driver is not at
fault here. Since the issue is hard to reproduce I couldn't determine
(yet) whether the controller only sends a partial command complete
event or if data is lost by the UART.

This problem can be investigated separately, I'll send an updated
version of this patch soon.

Thanks

Matthias

On Wed, Mar 06, 2019 at 04:40:41PM -0800, Matthias Kaehlcke wrote:
> Firmware download to the WCN3990 often fails with a 'TLV response size
> mismatch' error:
> 
> [  133.064659] Bluetooth: hci0: setting up wcn3990
> [  133.489150] Bluetooth: hci0: QCA controller version 0x02140201
> [  133.495245] Bluetooth: hci0: QCA Downloading qca/crbtfw21.tlv
> [  133.507214] Bluetooth: hci0: QCA TLV response size mismatch
> [  133.513265] Bluetooth: hci0: QCA Failed to download patch (-84)
> 
> This is caused by a vendor event that corresponds to an earlier command
> to change the baudrate. The event is not processed in the context of the
> baudrate change and later interpreted as response to the firmware
> download command (which is also a vendor command), but the driver detects
> that the event doesn't have the expected amount of associated data.
> 
> More details:
> 
> For the WCN3990 the vendor command for a baudrate change isn't sent as
> synchronous HCI command, because the controller sends the corresponding
> vendor event with the new baudrate. The event is received and decoded
> after the baudrate change of the host port.
> 
> Identify the 'unused' event when it is received and don't add it to
> the queue of RX frames.
> 
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
> ---
>  drivers/bluetooth/hci_qca.c | 54 ++++++++++++++++++++++++++++++++++---
>  1 file changed, 51 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index ab8e59419dbc4..565681a6a1167 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -30,6 +30,7 @@
>  
>  #include <linux/kernel.h>
>  #include <linux/clk.h>
> +#include <linux/completion.h>
>  #include <linux/debugfs.h>
>  #include <linux/delay.h>
>  #include <linux/device.h>
> @@ -55,6 +56,7 @@
>  #define HCI_MAX_IBS_SIZE	10
>  
>  #define QCA_IN_BAND_SLEEP_ENABLED	BIT(0)
> +#define QCA_DROP_VENDOR_EVENT		BIT(1)
>  
>  #define IBS_WAKE_RETRANS_TIMEOUT_MS	100
>  #define IBS_TX_IDLE_TIMEOUT_MS		2000
> @@ -108,6 +110,7 @@ struct qca_data {
>  	struct work_struct ws_rx_vote_off;
>  	struct work_struct ws_tx_vote_off;
>  	unsigned long flags;
> +	struct completion drop_ev_comp;
>  
>  	/* For debugging purpose */
>  	u64 ibs_sent_wacks;
> @@ -474,6 +477,7 @@ static int qca_open(struct hci_uart *hu)
>  	INIT_WORK(&qca->ws_tx_vote_off, qca_wq_serial_tx_clock_vote_off);
>  
>  	qca->hu = hu;
> +	init_completion(&qca->drop_ev_comp);
>  
>  	/* Assume we start with both sides asleep -- extra wakes OK */
>  	qca->tx_ibs_state = HCI_IBS_TX_ASLEEP;
> @@ -866,6 +870,33 @@ static int qca_recv_acl_data(struct hci_dev *hdev, struct sk_buff *skb)
>  	return hci_recv_frame(hdev, skb);
>  }
>  
> +static int qca_recv_event(struct hci_dev *hdev, struct sk_buff *skb)
> +{
> +	struct hci_uart *hu = hci_get_drvdata(hdev);
> +	struct qca_data *qca = hu->priv;
> +
> +	if (test_bit(QCA_DROP_VENDOR_EVENT, &qca->flags)) {
> +		struct hci_event_hdr *hdr = (void *)skb->data;
> +
> +		/* For the WCN3990 the vendor command for a baudrate change
> +		 * isn't sent as synchronous HCI command, because the
> +		 * controller sends the corresponding vendor event with the
> +		 * new baudrate. The event is received and properly decoded
> +		 * after changing the baudrate of the host port. It needs to
> +		 * be dropped, otherwise it can be mis-interpreted as
> +		 * response to a later firmware download command (also a
> +		 * vendor command).
> +		 */
> +
> +		if (hdr->evt == HCI_EV_VENDOR)
> +			complete(&qca->drop_ev_comp);
> +
> +		return 0;
> +	}
> +
> +	return hci_recv_frame(hdev, skb);
> +}
> +
>  #define QCA_IBS_SLEEP_IND_EVENT \
>  	.type = HCI_IBS_SLEEP_IND, \
>  	.hlen = 0, \
> @@ -890,7 +921,7 @@ static int qca_recv_acl_data(struct hci_dev *hdev, struct sk_buff *skb)
>  static const struct h4_recv_pkt qca_recv_pkts[] = {
>  	{ H4_RECV_ACL,             .recv = qca_recv_acl_data },
>  	{ H4_RECV_SCO,             .recv = hci_recv_frame    },
> -	{ H4_RECV_EVENT,           .recv = hci_recv_frame    },
> +	{ H4_RECV_EVENT,           .recv = qca_recv_event    },
>  	{ QCA_IBS_WAKE_IND_EVENT,  .recv = qca_ibs_wake_ind  },
>  	{ QCA_IBS_WAKE_ACK_EVENT,  .recv = qca_ibs_wake_ack  },
>  	{ QCA_IBS_SLEEP_IND_EVENT, .recv = qca_ibs_sleep_ind },
> @@ -1091,6 +1122,7 @@ static int qca_set_speed(struct hci_uart *hu, enum qca_speed_type speed_type)
>  {
>  	unsigned int speed, qca_baudrate;
>  	struct qca_serdev *qcadev;
> +	struct qca_data *qca = hu->priv;
>  	int ret = 0;
>  
>  	if (speed_type == QCA_INIT_SPEED) {
> @@ -1106,8 +1138,11 @@ static int qca_set_speed(struct hci_uart *hu, enum qca_speed_type speed_type)
>  		 * changing the baudrate of chip and host.
>  		 */
>  		qcadev = serdev_device_get_drvdata(hu->serdev);
> -		if (qcadev->btsoc_type == QCA_WCN3990)
> +		if (qcadev->btsoc_type == QCA_WCN3990) {
>  			hci_uart_set_flow_control(hu, true);
> +			reinit_completion(&qca->drop_ev_comp);
> +			set_bit(QCA_DROP_VENDOR_EVENT, &qca->flags);
> +		}
>  
>  		qca_baudrate = qca_get_baudrate_value(speed);
>  		bt_dev_dbg(hu->hdev, "Set UART speed to %d", speed);
> @@ -1118,8 +1153,21 @@ static int qca_set_speed(struct hci_uart *hu, enum qca_speed_type speed_type)
>  		host_set_baudrate(hu, speed);
>  
>  error:
> -		if (qcadev->btsoc_type == QCA_WCN3990)
> +		if (qcadev->btsoc_type == QCA_WCN3990) {
>  			hci_uart_set_flow_control(hu, false);
> +
> +			/* Wait for the controller to send the vendor event
> +			 * for the baudrate change command.
> +			 */
> +			if (!wait_for_completion_timeout(&qca->drop_ev_comp,
> +						 msecs_to_jiffies(100))) {
> +				bt_dev_err(hu->hdev,
> +					   "Failed to change controller baudrate\n");
> +				ret = -EPROTO;
> +			}
> +
> +			clear_bit(QCA_DROP_VENDOR_EVENT, &qca->flags);
> +		}
>  	}
>  
>  	return ret;