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Subject: Re: [PATCH] Bluetooth: btusb: hci_event: handle msbc audio over USB
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From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <1569476123-9951-1-git-send-email-amit.k.bag@intel.com>
Date:   Thu, 26 Sep 2019 08:24:35 +0200
Cc:     Bluez mailing list <linux-bluetooth@vger.kernel.org>,
        ravishankar.srivatsa@intel.com, chethan.tumkur.narayan@intel.com,
        Sathish Narasimman <sathish.narasimman@intel.com>,
        Raghuram Hegde <raghuram.hegde@intel.com>,
        Hsin-Yu Chao <hychao@chromium.org>
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Message-Id: <1DA34553-082C-4C58-ABCC-6CFAA9E3DF3A@holtmann.org>
References: <1569476123-9951-1-git-send-email-amit.k.bag@intel.com>
To:     Amit K Bag <amit.k.bag@intel.com>
Sender: linux-bluetooth-owner@vger.kernel.org
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Hi Amit,

> For msbc encoded audio stream over usb transport, btusb driver
> to be set to alternate settings 6 as per BT core spec 5.0. This
> done from  hci_sync_conn_complete_evt.  The type of air mode is known
> during this event.  For this reason the btusb is to be notifed
> about the TRANSPARENT air mode and the ALT setting 6 is selected.
> The changes are made considering some discussion over the similar
> patch submitted earlier from Kuba Pawlak(link below)
> https://www.spinics.net/lists/linux-bluetooth/msg64577.html
> 
> (am from https://www.spinics.net/lists/linux-bluetooth/msg76982.html)
> 
> Signed-off-by: Chethan T N <chethan.tumkur.narayan@intel.com>
> Signed-off-by: Sathish Narasimman <sathish.narasimman@intel.com>
> Signed-off-by: Raghuram Hegde <raghuram.hegde@intel.com>
> Signed-off-by: Hsin-Yu Chao <hychao@chromium.org>
> Signed-off-by: Amit K Bag <amit.k.bag@intel.com>
> ---
> drivers/bluetooth/btusb.c   | 145 ++++++++++++++++++++++++++++++--------------
> include/net/bluetooth/hci.h |   1 +
> net/bluetooth/hci_event.c   |   5 ++
> 3 files changed, 106 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> index a9c35ebb30f8..368cc93cb17e 100644
> --- a/drivers/bluetooth/btusb.c
> +++ b/drivers/bluetooth/btusb.c
> @@ -57,6 +57,9 @@ static struct usb_driver btusb_driver;
> #define BTUSB_IFNUM_2		0x80000
> #define BTUSB_CW6622		0x100000
> #define BTUSB_MEDIATEK		0x200000
> +#define BTUSB_ALT6_FLOW_CNTRL	6
> +
> +static int set_hci_packet_interval_flow = BTUSB_ALT6_FLOW_CNTRL;

this can never be a global variable. We allow multiple devices be attached to the same host. You need to move this into btusb_data struct.

> 
> static const struct usb_device_id btusb_table[] = {
> 	/* Generic Bluetooth USB device */
> @@ -974,6 +977,38 @@ static void btusb_isoc_complete(struct urb *urb)
> 	}
> }
> 
> +static inline void __fill_isoc_descriptor_msbc(struct urb *urb, int len,
> +					       int mtu)
> +{
> +	int i, offset = 0;
> +
> +	/* For msbc ALT 6 setting the host will send the packet at continuous
> +	 * flow. As per core spec 5, vol 4, part B, table 2.1. For ALT setting
> +	 * 6 the HCI PACKET INTERVAL should be 7.5ms for every usb packets.
> +	 * To maintain the rate we send 63bytes of usb packets alternatively for
> +	 * 7ms and 8ms to maintain the rate as 7.5ms.
> +	 */
> +	if (set_hci_packet_interval_flow == 6)
> +		set_hci_packet_interval_flow = 7;
> +	else if (set_hci_packet_interval_flow == 7)
> +		set_hci_packet_interval_flow = 6;

can’t this just be a bool that you just toggle.

> +
> +	BT_DBG("len %d mtu %d", len, mtu);
> +
> +	for (i = 0; i < set_hci_packet_interval_flow; i++) {
> +		urb->iso_frame_desc[i].offset = offset;
> +		urb->iso_frame_desc[i].length = offset;
> +	}
> +
> +	if (len && i < BTUSB_MAX_ISOC_FRAMES) {
> +		urb->iso_frame_desc[i].offset = offset;
> +		urb->iso_frame_desc[i].length = len;
> +		i++;
> +	}
> +
> +	urb->number_of_packets = i;
> +}
> +
> static inline void __fill_isoc_descriptor(struct urb *urb, int len, int mtu)
> {
> 	int i, offset = 0;
> @@ -1376,9 +1411,12 @@ static struct urb *alloc_isoc_urb(struct hci_dev *hdev, struct sk_buff *skb)
> 
> 	urb->transfer_flags  = URB_ISO_ASAP;
> 
> -	__fill_isoc_descriptor(urb, skb->len,
> +	if (data->isoc_altsetting == 6)
> +		__fill_isoc_descriptor_msbc(urb, skb->len,
> +			       le16_to_cpu(data->isoc_tx_ep->wMaxPacketSize));
> +	else
> +		__fill_isoc_descriptor(urb, skb->len,
> 			       le16_to_cpu(data->isoc_tx_ep->wMaxPacketSize));
> -
> 	skb->dev = (void *)hdev;
> 
> 	return urb;
> @@ -1466,18 +1504,6 @@ static int btusb_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
> 	return -EILSEQ;
> }
> 
> -static void btusb_notify(struct hci_dev *hdev, unsigned int evt)
> -{
> -	struct btusb_data *data = hci_get_drvdata(hdev);
> -
> -	BT_DBG("%s evt %d", hdev->name, evt);
> -
> -	if (hci_conn_num(hdev, SCO_LINK) != data->sco_num) {
> -		data->sco_num = hci_conn_num(hdev, SCO_LINK);
> -		schedule_work(&data->work);
> -	}
> -}
> -
> static inline int __set_isoc_interface(struct hci_dev *hdev, int altsetting)
> {
> 	struct btusb_data *data = hci_get_drvdata(hdev);
> @@ -1521,6 +1547,65 @@ static inline int __set_isoc_interface(struct hci_dev *hdev, int altsetting)
> 	return 0;
> }
> 
> +static int bt_switch_alt_setting(struct hci_dev *hdev, int new_alts)
> +{
> +	struct btusb_data *data = hci_get_drvdata(hdev);
> +	int err;
> +
> +	if (data->isoc_altsetting != new_alts) {
> +		unsigned long flags;
> +
> +		clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
> +		usb_kill_anchored_urbs(&data->isoc_anchor);
> +
> +		/* When isochronous alternate setting needs to be
> +		 * changed, because SCO connection has been added
> +		 * or removed, a packet fragment may be left in the
> +		 * reassembling state. This could lead to wrongly
> +		 * assembled fragments.
> +		 *
> +		 * Clear outstanding fragment when selecting a new
> +		 * alternate setting.
> +		 */
> +		spin_lock_irqsave(&data->rxlock, flags);
> +		kfree_skb(data->sco_skb);
> +		data->sco_skb = NULL;
> +		spin_unlock_irqrestore(&data->rxlock, flags);
> +
> +		err = __set_isoc_interface(hdev, new_alts);
> +		if (err < 0)
> +			return err;
> +	}
> +	if (!test_and_set_bit(BTUSB_ISOC_RUNNING, &data->flags)) {
> +		if (btusb_submit_isoc_urb(hdev, GFP_KERNEL) < 0)
> +			clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
> +		else
> +			btusb_submit_isoc_urb(hdev, GFP_KERNEL);
> +	}
> +
> +	return 0;
> +}
> +
> +static void btusb_notify(struct hci_dev *hdev, unsigned int evt)
> +{
> +	struct btusb_data *data = hci_get_drvdata(hdev);
> +
> +	BT_DBG("%s evt %d", hdev->name, evt);
> +
> +	if (hci_conn_num(hdev, SCO_LINK) != data->sco_num) {
> +		data->sco_num = hci_conn_num(hdev, SCO_LINK);
> +		schedule_work(&data->work);
> +	}

Since the internal processing of packets moved from a tasklet to a workqueue, I think the extra workqueue inside btusb can be actually removed. So I would get rid of this also for the non-mSBC case.

> +
> +	if (evt == HCI_NOTIFY_AIR_MODE_TRANSP) {
> +		/* Alt setting 6 is used for msbc encoded
> +		 * audio channel
> +		 */
> +		if (bt_switch_alt_setting(hdev, 6) < 0)
> +			BT_ERR("%s Set USB Alt6 failed", hdev->name);
> +	}
> +}
> +

I think this is really a one or the other. If the controller supports alternate setting 6 (which you actually have to check first) and it is air mode transparent then switch to alternate setting 6. Otherwise do what we have done before.

> static void btusb_work(struct work_struct *work)
> {
> 	struct btusb_data *data = container_of(work, struct btusb_data, work);
> @@ -1547,37 +1632,7 @@ static void btusb_work(struct work_struct *work)
> 		} else {
> 			new_alts = data->sco_num;
> 		}
> -
> -		if (data->isoc_altsetting != new_alts) {
> -			unsigned long flags;
> -
> -			clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
> -			usb_kill_anchored_urbs(&data->isoc_anchor);
> -
> -			/* When isochronous alternate setting needs to be
> -			 * changed, because SCO connection has been added
> -			 * or removed, a packet fragment may be left in the
> -			 * reassembling state. This could lead to wrongly
> -			 * assembled fragments.
> -			 *
> -			 * Clear outstanding fragment when selecting a new
> -			 * alternate setting.
> -			 */
> -			spin_lock_irqsave(&data->rxlock, flags);
> -			kfree_skb(data->sco_skb);
> -			data->sco_skb = NULL;
> -			spin_unlock_irqrestore(&data->rxlock, flags);
> -
> -			if (__set_isoc_interface(hdev, new_alts) < 0)
> -				return;
> -		}
> -
> -		if (!test_and_set_bit(BTUSB_ISOC_RUNNING, &data->flags)) {
> -			if (btusb_submit_isoc_urb(hdev, GFP_KERNEL) < 0)
> -				clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
> -			else
> -				btusb_submit_isoc_urb(hdev, GFP_KERNEL);
> -		}
> +		bt_switch_alt_setting(hdev, new_alts);
> 	} else {
> 		clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
> 		usb_kill_anchored_urbs(&data->isoc_anchor);
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index 5bc1e30dedde..89ac29f1dffa 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -52,6 +52,7 @@
> #define HCI_NOTIFY_CONN_ADD		1
> #define HCI_NOTIFY_CONN_DEL		2
> #define HCI_NOTIFY_VOICE_SETTING	3
> +#define HCI_NOTIFY_AIR_MODE_TRANSP	4
> 
> /* HCI bus types */
> #define HCI_VIRTUAL	0
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index c1d3a303d97f..1c268932422c 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -4231,6 +4231,11 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev,
> 		break;
> 	}
> 
> +	if (ev->air_mode == SCO_AIRMODE_TRANSP) {
> +		if (hdev->notify)
> +			hdev->notify(hdev, HCI_NOTIFY_AIR_MODE_TRANSP);
> +	}
> +

So this might work, but causes the USB subsystem to change the alternate setting twice. Once for CONN_ADD and once for SCO_AIRMODE_TRANSP. I prefer we just change the alternate setting once.

Maybe it is better to change CONN_ADD and CONN_DEL to an explicit ENABLE_SCO_CVSD and ENABLE_SCO_TRANSP and DISABLE_SCO.

Regards

Marcel