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Subject[PATCH] Bluetooth: Ignore CC events not matching the last HCI command
Date
This commit makes the kernel not send the next queued HCI command until
a command complete arrives for the last HCI command sent to the
controller. This change avoids a problem with some buggy controllers
(seen on two SKUs of QCA9377) that send an extra command complete event
for the previous command after the kernel had already sent a new HCI
command to the controller.

The problem was reproduced when starting an active scanning procedure,
where an extra command complete event arrives for the LE_SET_RANDOM_ADDR
command. When this happends the kernel ends up not processing the
command complete for the following commmand, LE_SET_SCAN_PARAM, and
ultimately behaving as if a passive scanning procedure was being
performed, when in fact controller is performing an active scanning
procedure. This makes it impossible to discover BLE devices as no device
found events are sent to userspace.

This problem is reproducible on 100% of the attempts on the affected
controllers. The extra command complete event can be seen at timestamp
27.420131 on the btmon logs bellow.

Bluetooth monitor ver 5.50
= Note: Linux version 5.0.0+ (x86_64) 0.352340
= Note: Bluetooth subsystem version 2.22 0.352343
= New Index: 80:C5:F2:8F:87:84 (Primary,USB,hci0) [hci0] 0.352344
= Open Index: 80:C5:F2:8F:87:84 [hci0] 0.352345
= Index Info: 80:C5:F2:8F:87:84 (Qualcomm) [hci0] 0.352346
@ MGMT Open: bluetoothd (privileged) version 1.14 {0x0001} 0.352347
@ MGMT Open: btmon (privileged) version 1.14 {0x0002} 0.352366
@ MGMT Open: btmgmt (privileged) version 1.14 {0x0003} 27.302164
@ MGMT Command: Start Discovery (0x0023) plen 1 {0x0003} [hci0] 27.302310
Address type: 0x06
LE Public
LE Random
< HCI Command: LE Set Random Address (0x08|0x0005) plen 6 #1 [hci0] 27.302496
Address: 15:60:F2:91:B2:24 (Non-Resolvable)
> HCI Event: Command Complete (0x0e) plen 4 #2 [hci0] 27.419117
LE Set Random Address (0x08|0x0005) ncmd 1
Status: Success (0x00)
< HCI Command: LE Set Scan Parameters (0x08|0x000b) plen 7 #3 [hci0] 27.419244
Type: Active (0x01)
Interval: 11.250 msec (0x0012)
Window: 11.250 msec (0x0012)
Own address type: Random (0x01)
Filter policy: Accept all advertisement (0x00)
> HCI Event: Command Complete (0x0e) plen 4 #4 [hci0] 27.420131
LE Set Random Address (0x08|0x0005) ncmd 1
Status: Success (0x00)
< HCI Command: LE Set Scan Enable (0x08|0x000c) plen 2 #5 [hci0] 27.420259
Scanning: Enabled (0x01)
Filter duplicates: Enabled (0x01)
> HCI Event: Command Complete (0x0e) plen 4 #6 [hci0] 27.420969
LE Set Scan Parameters (0x08|0x000b) ncmd 1
Status: Success (0x00)
> HCI Event: Command Complete (0x0e) plen 4 #7 [hci0] 27.421983
LE Set Scan Enable (0x08|0x000c) ncmd 1
Status: Success (0x00)
@ MGMT Event: Command Complete (0x0001) plen 4 {0x0003} [hci0] 27.422059
Start Discovery (0x0023) plen 1
Status: Success (0x00)
Address type: 0x06
LE Public
LE Random
@ MGMT Event: Discovering (0x0013) plen 2 {0x0003} [hci0] 27.422067
Address type: 0x06
LE Public
LE Random
Discovery: Enabled (0x01)
@ MGMT Event: Discovering (0x0013) plen 2 {0x0002} [hci0] 27.422067
Address type: 0x06
LE Public
LE Random
Discovery: Enabled (0x01)
@ MGMT Event: Discovering (0x0013) plen 2 {0x0001} [hci0] 27.422067
Address type: 0x06
LE Public
LE Random
Discovery: Enabled (0x01)

Signed-off-by: João Paulo Rechi Vita <jprvita@endlessm.com>
---
net/bluetooth/hci_event.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 609fd6871c5a..b349fc2b4123 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3071,6 +3071,19 @@ static void hci_cmd_complete_evt(struct hci_dev *hdev, struct sk_buff *skb,
*opcode = __le16_to_cpu(ev->opcode);
*status = skb->data[sizeof(*ev)];

+ if (*opcode != HCI_OP_RESET && !hci_sent_cmd_data(hdev, *opcode)) {
+ /* Some buggy controllers generate an extra command complete
+ * event for the previous command after a new commend was
+ * already sent, so if the opcode does not match the last sent
+ * command we should ignore this event.
+ *
+ * HCI_OP_RESET is a special case handled in
+ * hci_req_cmd_complete.
+ */
+ bt_dev_err(hdev, "unexpected CC event opcode 0x%4.4x", *opcode);
+ return;
+ }
+
skb_pull(skb, sizeof(*ev));

switch (*opcode) {
--
2.20.1
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