RE: [PATCH v13 12/12] Bluetooth: Allow usb to auto-suspend when SCO use non-HCI transport

Hi Luiz,

-----Original Message-----
From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Sent: Thursday, September 2, 2021 5:24 AM
To: K, Kiran <redacted>
Cc: linux-bluetooth@vger.kernel.org; Tumkur Narayan, Chethan
[off-list ref]
Subject: Re: [PATCH v13 12/12] Bluetooth: Allow usb to auto-suspend when SCO
use non-HCI transport

Hi Kiran,

On Tue, Aug 31, 2021 at 4:54 AM Kiran K [off-list ref] wrote:

quoted

From: Chethan T N <redacted>

Currently usb tranport is not allowed to suspend when SCO over HCI
tranport is active.

This patch shall enable the usb tranport to suspend when SCO link use
non-HCI transport

Signed-off-by: Chethan T N <redacted>
Signed-off-by: Kiran K <redacted>
---

Notes:
    changes in v13:
    - suspend usb in HFP offload use case

 drivers/bluetooth/btintel.c       |  2 +-
 include/net/bluetooth/bluetooth.h |  4 ++++
 net/bluetooth/hci_event.c         | 20 +++++++++++---------
 net/bluetooth/sco.c               |  2 +-
 4 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/drivers/bluetooth/btintel.c b/drivers/bluetooth/btintel.c
index 6091b691ddc2..2d64e289cf6e 100644
--- a/drivers/bluetooth/btintel.c
+++ b/drivers/bluetooth/btintel.c

@@ -2215,7 +2215,7 @@ static int btintel_get_codec_config_data(struct

hci_dev *hdev,  static int btintel_get_data_path_id(struct hci_dev
*hdev, __u8 *data_path_id)  {
        /* Intel uses 1 as data path id for all the usecases */
-       *data_path_id = 1;
+       *data_path_id = BT_SCO_PCM_PATH;
        return 0;
 }

diff --git a/include/net/bluetooth/bluetooth.h

b/include/net/bluetooth/bluetooth.h
index c1fa90fb7502..9e2745863b33 100644

--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h

@@ -177,6 +177,10 @@ struct bt_codecs {
 #define CODING_FORMAT_TRANSPARENT      0x03
 #define CODING_FORMAT_MSBC             0x05

+/* Audio data transport path used for SCO */ #define BT_SCO_HCI_PATH
+0x00 #define BT_SCO_PCM_PATH 0x01

If this is in fact vendor specific perhaps you should be declared in btintel.h not
here.

This is defined the Host Controller Interface assigned numbers, page no.3 "Transport Layer"- https://btprodspecificationrefs.blob.core.windows.net/assigned-numbers/Assigned%20Number%20Types/Host%20Controller%20Interface.pdf. So defined in bluetooth.h, let me know if you think otherwise.

quoted

+
 __printf(1, 2)
 void bt_info(const char *fmt, ...);
 __printf(1, 2)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index b48e24629fa4..7ff11cba89cf 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c

@@ -4516,15 +4516,17 @@ static void hci_sync_conn_complete_evt(struct

hci_dev *hdev,

        bt_dev_dbg(hdev, "SCO connected with air mode: %02x",
ev->air_mode);

-       switch (ev->air_mode) {
-       case 0x02:
-               if (hdev->notify)
-                       hdev->notify(hdev, HCI_NOTIFY_ENABLE_SCO_CVSD);
-               break;
-       case 0x03:
-               if (hdev->notify)
-                       hdev->notify(hdev, HCI_NOTIFY_ENABLE_SCO_TRANSP);
-               break;
+       if (conn->codec.data_path == BT_SCO_HCI_PATH) {
+               switch (ev->air_mode) {
+               case 0x02:
+                       if (hdev->notify)
+                               hdev->notify(hdev, HCI_NOTIFY_ENABLE_SCO_CVSD);
+                       break;
+               case 0x03:
+                       if (hdev->notify)
+                               hdev->notify(hdev, HCI_NOTIFY_ENABLE_SCO_TRANSP);
+                       break;
+               }

Hmm I think we might need to notify the driver to enable PCM routing so the
likes of btusb can call usb_disable_endpoint/usb_enable_endpoint for example
since in theory userspace may choose to switch from 
offload and vice-versa, note without calling usb_disable_endpoint there might
not be much power saving after all since the endpoint will remain active or do
we actually have a good explanation why it shall not be called when using PCM
routing? Note that usb_set_interface will call usb_enable_interface that will
then call usb_enable_endpoint so perhaps we need to call
usb_disable_interface, either way we can't assume the platform will be
restricted to only use one or the other.

Ack, Does it make sense to define and notify events "HCI_NOTIFY_DISABLE_SCO_USB_INTF ", "HCI_NOTIFY_ENABLE_SCO_USB_INTF " accordingly and handle this in btusb driver by disabling/enabling the ISOC endpoint respectively. That will serve the purpose or switch between software to hardware.

quoted

        }

        hci_connect_cfm(conn, ev->status); diff --git
a/net/bluetooth/sco.c b/net/bluetooth/sco.c index
004bce2b5eca..f35c12ca6aa5 100644

--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c

@@ -506,7 +506,7 @@ static struct sock *sco_sock_alloc(struct net *net,

struct socket *sock,

quoted

        sco_pi(sk)->codec.id = CODING_FORMAT_CVSD;
        sco_pi(sk)->codec.cid = 0xffff;
        sco_pi(sk)->codec.vid = 0xffff;
-       sco_pi(sk)->codec.data_path = 0x00;
+       sco_pi(sk)->codec.data_path = BT_SCO_HCI_PATH;

        bt_sock_link(&sco_sk_list, sk);
        return sk;
--
2.17.1

--
Luiz Augusto von Dentz