diff mbox series

[v5] Bluetooth: hci_core: Enable buffer flow control for SCO/eSCO

Message ID 20250304181019.214207-1-luiz.dentz@gmail.com (mailing list archive)
State New
Headers show
Series [v5] Bluetooth: hci_core: Enable buffer flow control for SCO/eSCO | expand

Checks

Context Check Description
tedd_an/pre-ci_am success Success
tedd_an/SubjectPrefix success Gitlint PASS
tedd_an/BuildKernel success BuildKernel PASS
tedd_an/CheckAllWarning success CheckAllWarning PASS
tedd_an/CheckSparse warning CheckSparse WARNING net/bluetooth/hci_event.c: note: in included file (through include/net/bluetooth/hci_core.h):
tedd_an/BuildKernel32 success BuildKernel32 PASS
tedd_an/TestRunnerSetup success TestRunnerSetup PASS
tedd_an/TestRunner_l2cap-tester success TestRunner PASS
tedd_an/TestRunner_iso-tester success TestRunner PASS
tedd_an/TestRunner_bnep-tester success TestRunner PASS
tedd_an/TestRunner_mgmt-tester fail TestRunner_mgmt-tester: Total: 490, Passed: 483 (98.6%), Failed: 3, Not Run: 4
tedd_an/TestRunner_rfcomm-tester success TestRunner PASS
tedd_an/TestRunner_sco-tester success TestRunner PASS
tedd_an/TestRunner_ioctl-tester success TestRunner PASS
tedd_an/TestRunner_mesh-tester success TestRunner PASS
tedd_an/TestRunner_smp-tester success TestRunner PASS
tedd_an/TestRunner_userchan-tester success TestRunner PASS

Commit Message

Luiz Augusto von Dentz March 4, 2025, 6:10 p.m. UTC
From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

This enables buffer flow control for SCO/eSCO
(see: Bluetooth Core 6.0 spec: 6.22. Synchronous Flow Control Enable),
recently this has caused the following problem and is actually a nice
addition for the likes of Socket TX complete:

< HCI Command: Read Buffer Size (0x04|0x0005) plen 0
> HCI Event: Command Complete (0x0e) plen 11
      Read Buffer Size (0x04|0x0005) ncmd 1
        Status: Success (0x00)
        ACL MTU: 1021 ACL max packet: 5
        SCO MTU: 240  SCO max packet: 8
...
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
> HCI Event: Hardware Error (0x10) plen 1
        Code: 0x0a

Fixes: 7fedd3bb6b77 ("Bluetooth: Prioritize SCO traffic")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 include/net/bluetooth/hci.h      |  6 ++++
 include/net/bluetooth/hci_core.h |  1 +
 net/bluetooth/hci_core.c         | 54 +++++++++++++-------------------
 net/bluetooth/hci_event.c        |  5 +++
 net/bluetooth/hci_sync.c         | 18 +++++++++++
 5 files changed, 52 insertions(+), 32 deletions(-)

Comments

bluez.test.bot@gmail.com March 4, 2025, 6:37 p.m. UTC | #1
This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=940193

---Test result---

Test Summary:
CheckPatch                    PENDING   0.31 seconds
GitLint                       PENDING   0.26 seconds
SubjectPrefix                 PASS      1.21 seconds
BuildKernel                   PASS      26.47 seconds
CheckAllWarning               PASS      26.99 seconds
CheckSparse                   WARNING   30.29 seconds
BuildKernel32                 PASS      24.21 seconds
TestRunnerSetup               PASS      426.84 seconds
TestRunner_l2cap-tester       PASS      22.86 seconds
TestRunner_iso-tester         PASS      34.33 seconds
TestRunner_bnep-tester        PASS      5.41 seconds
TestRunner_mgmt-tester        FAIL      119.90 seconds
TestRunner_rfcomm-tester      PASS      7.99 seconds
TestRunner_sco-tester         PASS      11.72 seconds
TestRunner_ioctl-tester       PASS      8.26 seconds
TestRunner_mesh-tester        PASS      6.77 seconds
TestRunner_smp-tester         PASS      8.23 seconds
TestRunner_userchan-tester    PASS      4.95 seconds
IncrementalBuild              PENDING   0.85 seconds

Details
##############################
Test: CheckPatch - PENDING
Desc: Run checkpatch.pl script
Output:

##############################
Test: GitLint - PENDING
Desc: Run gitlint
Output:

##############################
Test: CheckSparse - WARNING
Desc: Run sparse tool with linux kernel
Output:
net/bluetooth/hci_event.c: note: in included file (through include/net/bluetooth/hci_core.h):
##############################
Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Output:
Total: 490, Passed: 483 (98.6%), Failed: 3, Not Run: 4

Failed Test Cases
LL Privacy - Add Device 2 (2 Devices to AL)          Failed       0.175 seconds
LL Privacy - Add Device 3 (AL is full)               Failed       0.196 seconds
LL Privacy - Set Device Flag 1 (Device Privacy)      Failed       0.147 seconds
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth
Luiz Augusto von Dentz March 4, 2025, 8:24 p.m. UTC | #2
Hi,

On Tue, Mar 4, 2025 at 1:10 PM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
>
> This enables buffer flow control for SCO/eSCO
> (see: Bluetooth Core 6.0 spec: 6.22. Synchronous Flow Control Enable),
> recently this has caused the following problem and is actually a nice
> addition for the likes of Socket TX complete:
>
> < HCI Command: Read Buffer Size (0x04|0x0005) plen 0
> > HCI Event: Command Complete (0x0e) plen 11
>       Read Buffer Size (0x04|0x0005) ncmd 1
>         Status: Success (0x00)
>         ACL MTU: 1021 ACL max packet: 5
>         SCO MTU: 240  SCO max packet: 8
> ...
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> < SCO Data TX: Handle 257 flags 0x00 dlen 120
> > HCI Event: Hardware Error (0x10) plen 1
>         Code: 0x0a
>
> Fixes: 7fedd3bb6b77 ("Bluetooth: Prioritize SCO traffic")
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> ---
>  include/net/bluetooth/hci.h      |  6 ++++
>  include/net/bluetooth/hci_core.h |  1 +
>  net/bluetooth/hci_core.c         | 54 +++++++++++++-------------------
>  net/bluetooth/hci_event.c        |  5 +++
>  net/bluetooth/hci_sync.c         | 18 +++++++++++
>  5 files changed, 52 insertions(+), 32 deletions(-)
>
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index b99818df8ee7..70169533c940 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -448,6 +448,7 @@ enum {
>         HCI_WIDEBAND_SPEECH_ENABLED,
>         HCI_EVENT_FILTER_CONFIGURED,
>         HCI_PA_SYNC,
> +       HCI_SCO_FLOWCTL,
>
>         HCI_DUT_MODE,
>         HCI_VENDOR_DIAG,
> @@ -1544,6 +1545,11 @@ struct hci_rp_read_tx_power {
>         __s8     tx_power;
>  } __packed;
>
> +#define HCI_OP_WRITE_SYNC_FLOWCTL      0x0c2f
> +struct hci_cp_write_sync_flowctl {
> +       __u8     enable;
> +} __packed;
> +
>  #define HCI_OP_READ_PAGE_SCAN_TYPE     0x0c46
>  struct hci_rp_read_page_scan_type {
>         __u8     status;
> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
> index 2f320eeddfec..cf18cf65fe5e 100644
> --- a/include/net/bluetooth/hci_core.h
> +++ b/include/net/bluetooth/hci_core.h
> @@ -1857,6 +1857,7 @@ void hci_conn_del_sysfs(struct hci_conn *conn);
>  #define lmp_hold_capable(dev)      ((dev)->features[0][0] & LMP_HOLD)
>  #define lmp_sniff_capable(dev)     ((dev)->features[0][0] & LMP_SNIFF)
>  #define lmp_park_capable(dev)      ((dev)->features[0][1] & LMP_PARK)
> +#define lmp_sco_capable(dev)       ((dev)->features[0][1] & LMP_SCO)
>  #define lmp_inq_rssi_capable(dev)  ((dev)->features[0][3] & LMP_RSSI_INQ)
>  #define lmp_esco_capable(dev)      ((dev)->features[0][3] & LMP_ESCO)
>  #define lmp_bredr_capable(dev)     (!((dev)->features[0][4] & LMP_NO_BREDR))
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index e7ec12437c8b..9ea9b4091f8f 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -3548,45 +3548,35 @@ static void __check_timeout(struct hci_dev *hdev, unsigned int cnt, u8 type)
>  }
>
>  /* Schedule SCO */
> -static void hci_sched_sco(struct hci_dev *hdev)
> +static void hci_sched_sco_type(struct hci_dev *hdev, __u8 type)
>  {
>         struct hci_conn *conn;
>         struct sk_buff *skb;
>         int quote;
> +       unsigned int pkts;
>
> -       BT_DBG("%s", hdev->name);
> +       bt_dev_dbg(hdev, "type %u", type);
>
> -       if (!hci_conn_num(hdev, SCO_LINK))
> +       if (!hci_conn_num(hdev, type))
>                 return;
>
> -       while (hdev->sco_cnt && (conn = hci_low_sent(hdev, SCO_LINK, &quote))) {
> +       /* Use sco_pkts if flow control has not been enabled yet which will
> +        * limit the amount of buffer sent in a row.
> +        */
> +       if (!hci_dev_test_flag(hdev, HCI_SCO_FLOWCTL))
> +               pkts = hdev->sco_pkts;
> +       else
> +               pkts = hdev->sco_cnt;
> +
> +       while (pkts && (conn = hci_low_sent(hdev, type, &quote))) {
>                 while (quote-- && (skb = skb_dequeue(&conn->data_q))) {
>                         BT_DBG("skb %p len %d", skb, skb->len);
>                         hci_send_frame(hdev, skb);
>
> -                       conn->sent++;
> -                       if (conn->sent == ~0)
> -                               conn->sent = 0;
> -               }
> -       }
> -}
> +                       pkts--;
>
> -static void hci_sched_esco(struct hci_dev *hdev)
> -{
> -       struct hci_conn *conn;
> -       struct sk_buff *skb;
> -       int quote;
> -
> -       BT_DBG("%s", hdev->name);
> -
> -       if (!hci_conn_num(hdev, ESCO_LINK))
> -               return;
> -
> -       while (hdev->sco_cnt && (conn = hci_low_sent(hdev, ESCO_LINK,
> -                                                    &quote))) {
> -               while (quote-- && (skb = skb_dequeue(&conn->data_q))) {
> -                       BT_DBG("skb %p len %d", skb, skb->len);
> -                       hci_send_frame(hdev, skb);
> +                       if (hdev->sco_cnt > 0)
> +                               hdev->sco_cnt--;
>
>                         conn->sent++;
>                         if (conn->sent == ~0)
> @@ -3628,8 +3618,8 @@ static void hci_sched_acl_pkt(struct hci_dev *hdev)
>                         chan->conn->sent++;
>
>                         /* Send pending SCO packets right away */
> -                       hci_sched_sco(hdev);
> -                       hci_sched_esco(hdev);
> +                       hci_sched_sco_type(hdev, SCO_LINK);
> +                       hci_sched_sco_type(hdev, ESCO_LINK);
>                 }
>         }
>
> @@ -3684,8 +3674,8 @@ static void hci_sched_le(struct hci_dev *hdev)
>                         chan->conn->sent++;
>
>                         /* Send pending SCO packets right away */
> -                       hci_sched_sco(hdev);
> -                       hci_sched_esco(hdev);
> +                       hci_sched_sco_type(hdev, SCO_LINK);
> +                       hci_sched_sco_type(hdev, ESCO_LINK);
>                 }
>         }
>
> @@ -3730,8 +3720,8 @@ static void hci_tx_work(struct work_struct *work)
>
>         if (!hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
>                 /* Schedule queues and send stuff to HCI driver */
> -               hci_sched_sco(hdev);
> -               hci_sched_esco(hdev);
> +               hci_sched_sco_type(hdev, SCO_LINK);
> +               hci_sched_sco_type(hdev, ESCO_LINK);
>                 hci_sched_iso(hdev);
>                 hci_sched_acl(hdev);
>                 hci_sched_le(hdev);
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 19e19c9f5e68..e6eadcc13484 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -4448,6 +4448,11 @@ static void hci_num_comp_pkts_evt(struct hci_dev *hdev, void *data,
>                         hdev->sco_cnt += count;
>                         if (hdev->sco_cnt > hdev->sco_pkts)
>                                 hdev->sco_cnt = hdev->sco_pkts;
> +
> +                       /* Enable HCI_SCO_FLOWCTL so sco_cnt is used instead of
> +                        * sco_pkts.
> +                        */
> +                       hci_dev_set_flag(hdev, HCI_SCO_FLOWCTL);

I may spin another version implement this logic but before triggering
hci_connect_cfm do send a empty packet just to test if flowctl is
really enabled, this maybe better than always setting the flag above
since in that case the socket interface is not involved so we can
guarantee that only one packet is outstanding.

>                         break;
>
>                 case ISO_LINK:
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index c4c2cf51b219..91cfb7c2cb08 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -3769,6 +3769,22 @@ static int hci_write_ca_timeout_sync(struct hci_dev *hdev)
>                                      sizeof(param), &param, HCI_CMD_TIMEOUT);
>  }
>
> +/* Enable SCO flow control if supported */
> +static int hci_write_sync_flowctl_sync(struct hci_dev *hdev)
> +{
> +       struct hci_cp_write_sync_flowctl cp;
> +
> +       /* Check if the controller supports SCO and HCI_OP_WRITE_SYNC_FLOWCTL */
> +       if (!lmp_sco_capable(hdev) || !(hdev->commands[10] & BIT(4)))
> +               return 0;
> +
> +       memset(&cp, 0, sizeof(cp));
> +       cp.enable = 0x01;
> +
> +       return __hci_cmd_sync_status(hdev, HCI_OP_WRITE_SYNC_FLOWCTL,
> +                                   sizeof(cp), &cp, HCI_CMD_TIMEOUT);
> +}
> +
>  /* BR Controller init stage 2 command sequence */
>  static const struct hci_init_stage br_init2[] = {
>         /* HCI_OP_READ_BUFFER_SIZE */
> @@ -3787,6 +3803,8 @@ static const struct hci_init_stage br_init2[] = {
>         HCI_INIT(hci_clear_event_filter_sync),
>         /* HCI_OP_WRITE_CA_TIMEOUT */
>         HCI_INIT(hci_write_ca_timeout_sync),
> +       /* HCI_OP_WRITE_SYNC_FLOWCTL */
> +       HCI_INIT(hci_write_sync_flowctl_sync),
>         {}
>  };
>
> --
> 2.48.1
>
diff mbox series

Patch

diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index b99818df8ee7..70169533c940 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -448,6 +448,7 @@  enum {
 	HCI_WIDEBAND_SPEECH_ENABLED,
 	HCI_EVENT_FILTER_CONFIGURED,
 	HCI_PA_SYNC,
+	HCI_SCO_FLOWCTL,
 
 	HCI_DUT_MODE,
 	HCI_VENDOR_DIAG,
@@ -1544,6 +1545,11 @@  struct hci_rp_read_tx_power {
 	__s8     tx_power;
 } __packed;
 
+#define HCI_OP_WRITE_SYNC_FLOWCTL	0x0c2f
+struct hci_cp_write_sync_flowctl {
+	__u8     enable;
+} __packed;
+
 #define HCI_OP_READ_PAGE_SCAN_TYPE	0x0c46
 struct hci_rp_read_page_scan_type {
 	__u8     status;
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 2f320eeddfec..cf18cf65fe5e 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -1857,6 +1857,7 @@  void hci_conn_del_sysfs(struct hci_conn *conn);
 #define lmp_hold_capable(dev)      ((dev)->features[0][0] & LMP_HOLD)
 #define lmp_sniff_capable(dev)     ((dev)->features[0][0] & LMP_SNIFF)
 #define lmp_park_capable(dev)      ((dev)->features[0][1] & LMP_PARK)
+#define lmp_sco_capable(dev)       ((dev)->features[0][1] & LMP_SCO)
 #define lmp_inq_rssi_capable(dev)  ((dev)->features[0][3] & LMP_RSSI_INQ)
 #define lmp_esco_capable(dev)      ((dev)->features[0][3] & LMP_ESCO)
 #define lmp_bredr_capable(dev)     (!((dev)->features[0][4] & LMP_NO_BREDR))
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index e7ec12437c8b..9ea9b4091f8f 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3548,45 +3548,35 @@  static void __check_timeout(struct hci_dev *hdev, unsigned int cnt, u8 type)
 }
 
 /* Schedule SCO */
-static void hci_sched_sco(struct hci_dev *hdev)
+static void hci_sched_sco_type(struct hci_dev *hdev, __u8 type)
 {
 	struct hci_conn *conn;
 	struct sk_buff *skb;
 	int quote;
+	unsigned int pkts;
 
-	BT_DBG("%s", hdev->name);
+	bt_dev_dbg(hdev, "type %u", type);
 
-	if (!hci_conn_num(hdev, SCO_LINK))
+	if (!hci_conn_num(hdev, type))
 		return;
 
-	while (hdev->sco_cnt && (conn = hci_low_sent(hdev, SCO_LINK, &quote))) {
+	/* Use sco_pkts if flow control has not been enabled yet which will
+	 * limit the amount of buffer sent in a row.
+	 */
+	if (!hci_dev_test_flag(hdev, HCI_SCO_FLOWCTL))
+		pkts = hdev->sco_pkts;
+	else
+		pkts = hdev->sco_cnt;
+
+	while (pkts && (conn = hci_low_sent(hdev, type, &quote))) {
 		while (quote-- && (skb = skb_dequeue(&conn->data_q))) {
 			BT_DBG("skb %p len %d", skb, skb->len);
 			hci_send_frame(hdev, skb);
 
-			conn->sent++;
-			if (conn->sent == ~0)
-				conn->sent = 0;
-		}
-	}
-}
+			pkts--;
 
-static void hci_sched_esco(struct hci_dev *hdev)
-{
-	struct hci_conn *conn;
-	struct sk_buff *skb;
-	int quote;
-
-	BT_DBG("%s", hdev->name);
-
-	if (!hci_conn_num(hdev, ESCO_LINK))
-		return;
-
-	while (hdev->sco_cnt && (conn = hci_low_sent(hdev, ESCO_LINK,
-						     &quote))) {
-		while (quote-- && (skb = skb_dequeue(&conn->data_q))) {
-			BT_DBG("skb %p len %d", skb, skb->len);
-			hci_send_frame(hdev, skb);
+			if (hdev->sco_cnt > 0)
+				hdev->sco_cnt--;
 
 			conn->sent++;
 			if (conn->sent == ~0)
@@ -3628,8 +3618,8 @@  static void hci_sched_acl_pkt(struct hci_dev *hdev)
 			chan->conn->sent++;
 
 			/* Send pending SCO packets right away */
-			hci_sched_sco(hdev);
-			hci_sched_esco(hdev);
+			hci_sched_sco_type(hdev, SCO_LINK);
+			hci_sched_sco_type(hdev, ESCO_LINK);
 		}
 	}
 
@@ -3684,8 +3674,8 @@  static void hci_sched_le(struct hci_dev *hdev)
 			chan->conn->sent++;
 
 			/* Send pending SCO packets right away */
-			hci_sched_sco(hdev);
-			hci_sched_esco(hdev);
+			hci_sched_sco_type(hdev, SCO_LINK);
+			hci_sched_sco_type(hdev, ESCO_LINK);
 		}
 	}
 
@@ -3730,8 +3720,8 @@  static void hci_tx_work(struct work_struct *work)
 
 	if (!hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
 		/* Schedule queues and send stuff to HCI driver */
-		hci_sched_sco(hdev);
-		hci_sched_esco(hdev);
+		hci_sched_sco_type(hdev, SCO_LINK);
+		hci_sched_sco_type(hdev, ESCO_LINK);
 		hci_sched_iso(hdev);
 		hci_sched_acl(hdev);
 		hci_sched_le(hdev);
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 19e19c9f5e68..e6eadcc13484 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4448,6 +4448,11 @@  static void hci_num_comp_pkts_evt(struct hci_dev *hdev, void *data,
 			hdev->sco_cnt += count;
 			if (hdev->sco_cnt > hdev->sco_pkts)
 				hdev->sco_cnt = hdev->sco_pkts;
+
+			/* Enable HCI_SCO_FLOWCTL so sco_cnt is used instead of
+			 * sco_pkts.
+			 */
+			hci_dev_set_flag(hdev, HCI_SCO_FLOWCTL);
 			break;
 
 		case ISO_LINK:
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index c4c2cf51b219..91cfb7c2cb08 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -3769,6 +3769,22 @@  static int hci_write_ca_timeout_sync(struct hci_dev *hdev)
 				     sizeof(param), &param, HCI_CMD_TIMEOUT);
 }
 
+/* Enable SCO flow control if supported */
+static int hci_write_sync_flowctl_sync(struct hci_dev *hdev)
+{
+	struct hci_cp_write_sync_flowctl cp;
+
+	/* Check if the controller supports SCO and HCI_OP_WRITE_SYNC_FLOWCTL */
+	if (!lmp_sco_capable(hdev) || !(hdev->commands[10] & BIT(4)))
+		return 0;
+
+	memset(&cp, 0, sizeof(cp));
+	cp.enable = 0x01;
+
+	return __hci_cmd_sync_status(hdev, HCI_OP_WRITE_SYNC_FLOWCTL,
+				    sizeof(cp), &cp, HCI_CMD_TIMEOUT);
+}
+
 /* BR Controller init stage 2 command sequence */
 static const struct hci_init_stage br_init2[] = {
 	/* HCI_OP_READ_BUFFER_SIZE */
@@ -3787,6 +3803,8 @@  static const struct hci_init_stage br_init2[] = {
 	HCI_INIT(hci_clear_event_filter_sync),
 	/* HCI_OP_WRITE_CA_TIMEOUT */
 	HCI_INIT(hci_write_ca_timeout_sync),
+	/* HCI_OP_WRITE_SYNC_FLOWCTL */
+	HCI_INIT(hci_write_sync_flowctl_sync),
 	{}
 };