Re: [PATCH v3 2/3] Bluetooth: btusb: Workaround for spotty SCO quality

[Luiz Augusto von Dentz]

Hi Hilda,

On Thu, Sep 29, 2022 at 4:44 AM <hildawu@xxxxxxxxxxx> wrote:
>
> From: Hilda Wu <hildawu@xxxxxxxxxxx>
>
> When streaming HFP, once a few minutes a brief pause in audio can be
> heard on some platform with Realtek Bluetooth. When the issue occurs,
> the system will see the SCO packet for unknown connection handle messages.

Please add the btmon trace to make it more clear what we are dealing with.

> Note: This issue affects (e)SCO only, does not affect ACLs.
> Because the duplicate packet causing the problem only occurs in Realtek BT.
> This is to filter out duplicate packet for avoiding influence.
>
> Signed-off-by: Alex Lu <alex_lu@xxxxxxxxxxxxxx>
> Signed-off-by: Hilda Wu <hildawu@xxxxxxxxxxx>
> ---
> Changes in v3:
>  - Use the vendor function to replace btus_recv_isoc
>  - Additional info: The comparison of btrtl_usb_recv_isoc here is for invalid handle,
>    the invalid handle shouldn't appear. So we try to find out the rule and filter out this.
>
> Changes in v2:
>  - Seperate commits for functions
> ---
> ---
>  drivers/bluetooth/btrtl.c | 27 ++++++++++++++
>  drivers/bluetooth/btrtl.h |  8 ++++
>  drivers/bluetooth/btusb.c | 77 ++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 111 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/bluetooth/btrtl.c b/drivers/bluetooth/btrtl.c
> index fb52313a1d45..272f90621a10 100644
> --- a/drivers/bluetooth/btrtl.c
> +++ b/drivers/bluetooth/btrtl.c
> @@ -937,6 +937,33 @@ int btrtl_get_uart_settings(struct hci_dev *hdev,
>  }
>  EXPORT_SYMBOL_GPL(btrtl_get_uart_settings);
>
> +int btrtl_usb_recv_isoc(u16 pos, u8 *data, u8 *p, int len,
> +                       u16 wMaxPacketSize)
> +{
> +       u8 *prev;
> +
> +       if (pos >= HCI_SCO_HDR_SIZE && pos >= wMaxPacketSize &&
> +           len == wMaxPacketSize && !(pos % wMaxPacketSize) &&
> +           wMaxPacketSize >= 10 && p[0] == data[0] && p[1] == data[1]) {
> +               prev = data + (pos - wMaxPacketSize);
> +
> +               /* Detect the sco data of usb isoc pkt duplication. */
> +               if (!memcmp(p + 2, prev + 2, 8))
> +                       return -EILSEQ;
> +
> +               if (wMaxPacketSize >= 12 &&
> +                   p[2] == prev[6] && p[3] == prev[7] &&
> +                   p[4] == prev[4] && p[5] == prev[5] &&
> +                   p[6] == prev[10] && p[7] == prev[11] &&
> +                   p[8] == prev[8] && p[9] == prev[9]) {
> +                       return -EILSEQ;
> +               }
> +       }

I'm really not getting what you trying to do above, if you want to
check if the handle is valid there use lookup function like we do for
example here:

https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git/tree/drivers/bluetooth/btusb.c#n937

It is sort of a layer violation though and probably wouldn't work with
the likes of the user channel because the stack may not be handling
the connections, so the alternative would be to store the handle
somewhere when we start processing the fragments and then make sure
every fragment matches the handle.

> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(btrtl_usb_recv_isoc);
> +
>  MODULE_AUTHOR("Daniel Drake <drake@xxxxxxxxxxxx>");
>  MODULE_DESCRIPTION("Bluetooth support for Realtek devices ver " VERSION);
>  MODULE_VERSION(VERSION);
> diff --git a/drivers/bluetooth/btrtl.h b/drivers/bluetooth/btrtl.h
> index ebf0101c959b..c9783e8fe0aa 100644
> --- a/drivers/bluetooth/btrtl.h
> +++ b/drivers/bluetooth/btrtl.h
> @@ -83,6 +83,8 @@ int btrtl_get_uart_settings(struct hci_dev *hdev,
>                             struct btrtl_device_info *btrtl_dev,
>                             unsigned int *controller_baudrate,
>                             u32 *device_baudrate, bool *flow_control);
> +int btrtl_usb_recv_isoc(u16 pos, u8 *data, u8 *buffer, int len,
> +                               u16 wMaxPacketSize);
>
>  #else
>
> @@ -126,4 +128,10 @@ static inline int btrtl_get_uart_settings(struct hci_dev *hdev,
>         return -ENOENT;
>  }
>
> +static inline int btrtl_usb_recv_isoc(u16 pos, u8 *data, u8 *buffer, int len,
> +                               u16 wMaxPacketSize)
> +{
> +       return -EOPNOTSUPP;
> +}
> +
>  #endif
> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> index 4c3aed89ff05..7583059e3b2c 100644
> --- a/drivers/bluetooth/btusb.c
> +++ b/drivers/bluetooth/btusb.c
> @@ -683,6 +683,7 @@ struct btusb_data {
>         int (*recv_event)(struct hci_dev *hdev, struct sk_buff *skb);
>         int (*recv_acl)(struct hci_dev *hdev, struct sk_buff *skb);
>         int (*recv_bulk)(struct btusb_data *data, void *buffer, int count);
> +       int (*recv_isoc)(struct btusb_data *data, void *buffer, int count);
>
>         int (*setup_on_usb)(struct hci_dev *hdev);
>
> @@ -1239,7 +1240,7 @@ static void btusb_isoc_complete(struct urb *urb)
>
>                         hdev->stat.byte_rx += length;
>
> -                       if (btusb_recv_isoc(data, urb->transfer_buffer + offset,
> +                       if (data->recv_isoc(data, urb->transfer_buffer + offset,
>                                             length) < 0) {
>                                 bt_dev_err(hdev, "corrupted SCO packet");
>                                 hdev->stat.err_rx++;
> @@ -2309,6 +2310,77 @@ static int btusb_send_frame_intel(struct hci_dev *hdev, struct sk_buff *skb)
>         return -EILSEQ;
>  }
>
> +static int btusb_recv_isoc_realtek(struct btusb_data *data, void *buffer,
> +                                  int count)
> +{
> +       struct sk_buff *skb;
> +       unsigned long flags;
> +       int err = 0;
> +       u16 wMaxPacketSize = le16_to_cpu(data->isoc_rx_ep->wMaxPacketSize);
> +
> +       spin_lock_irqsave(&data->rxlock, flags);
> +       skb = data->sco_skb;
> +
> +       while (count) {
> +               int len;
> +
> +               if (!skb) {
> +                       skb = bt_skb_alloc(HCI_MAX_SCO_SIZE, GFP_ATOMIC);
> +                       if (!skb) {
> +                               err = -ENOMEM;
> +                               break;
> +                       }
> +
> +                       hci_skb_pkt_type(skb) = HCI_SCODATA_PKT;
> +                       hci_skb_expect(skb) = HCI_SCO_HDR_SIZE;
> +               }
> +
> +               len = min_t(uint, hci_skb_expect(skb), count);
> +
> +               /* Gaps in audio could be heard while streaming WBS using USB
> +                * alt settings 3 on some platforms, since this is only used
> +                * with RTK chips so let vendor function detect it.
> +                */
> +               if (!btusb_find_altsetting(data, 6) &&
> +                       test_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags)) {
> +                       err = btrtl_usb_recv_isoc(skb->len, skb->data, buffer,
> +                                                       len, wMaxPacketSize);
> +                       if (err)
> +                               break;
> +               }
> +
> +               skb_put_data(skb, buffer, len);
> +
> +               count -= len;
> +               buffer += len;
> +               hci_skb_expect(skb) -= len;
> +
> +               if (skb->len == HCI_SCO_HDR_SIZE) {
> +                       /* Complete SCO header */
> +                       hci_skb_expect(skb) = hci_sco_hdr(skb)->dlen;
> +
> +                       if (skb_tailroom(skb) < hci_skb_expect(skb)) {
> +                               kfree_skb(skb);
> +                               skb = NULL;
> +
> +                               err = -EILSEQ;
> +                               break;
> +                       }
> +               }
> +
> +               if (!hci_skb_expect(skb)) {
> +                       /* Complete frame */
> +                       hci_recv_frame(data->hdev, skb);
> +                       skb = NULL;
> +               }
> +       }
> +
> +       data->sco_skb = skb;
> +       spin_unlock_irqrestore(&data->rxlock, flags);
> +
> +       return err;
> +}
> +
>  /* UHW CR mapping */
>  #define MTK_BT_MISC            0x70002510
>  #define MTK_BT_SUBSYS_RST      0x70002610
> @@ -3741,6 +3813,7 @@ static int btusb_probe(struct usb_interface *intf,
>
>         data->recv_event = hci_recv_frame;
>         data->recv_bulk = btusb_recv_bulk;
> +       data->recv_isoc = btusb_recv_isoc;
>
>         if (id->driver_info & BTUSB_INTEL_COMBINED) {
>                 /* Allocate extra space for Intel device */
> @@ -3914,6 +3987,8 @@ static int btusb_probe(struct usb_interface *intf,
>                 hdev->shutdown = btrtl_shutdown_realtek;
>                 hdev->cmd_timeout = btusb_rtl_cmd_timeout;
>
> +               data->recv_isoc = btusb_recv_isoc_realtek;
> +
>                 /* Realtek devices need to set remote wakeup on auto-suspend */
>                 set_bit(BTUSB_WAKEUP_AUTOSUSPEND, &data->flags);
>                 set_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags);
> --
> 2.17.1
>


-- 
Luiz Augusto von Dentz