[regression] Bluetooth: Query LE tx power on startup broke Bluetooth on MacBookPro16,1

[Orlando Chamberlain <redecorating@protonmail.com>]

Commit 7c395ea521e6 made Bluetooth stop working on the MacBookPro16,1. I

believe this also affected the iMac20,1. The patch below introduces a quirk

disabling Read LE Min/Max Tx Power for affected computers, based off the brcm
chip
 id 150.



I think there are a couple of issues with this patch that I don't have the

knowledge to resolve:

1. I don't know how accurate the description of the quirk is, I based it off

   the commit message of 7c395ea521e6m, however I don't understand much about

   how Bluetooth works. Other Bluetooth quirks also have explanations as to

   why they are needed, I don't know why this quirk is needed (is it that

   these chips incorrectly say they support read le minmax tx power? I just

   don't know).

2. It may be a bug in the min max le tx power code that could be fixed instead

   of disabling it for the affected devices.



I haven't had much success in figuring out exactly why reading le minmax tx

power stops Bluetooth from working. I have noticed that these lines are not

present in dmesg when Bluetooth is not working due to this issue:



Bluetooth: RFCOMM TTY layer initialized

Bluetooth: RFCOMM socket layer initialized

Bluetooth: RFCOMM ver 1.11



I have also added some logging around the changes in 7c395ea521e6, the two

patches (one with bt working one without) I tried and their associated dmesgs

are here https://gist.github.com/Redecorating/8330bb58a7cb8730be3956058ba4599f



Regards,

Orlando Chamberlain



---

 drivers/bluetooth/btbcm.c   | 4 ++++

 include/net/bluetooth/hci.h | 9 +++++++++

 net/bluetooth/hci_core.c    | 3 ++-

 3 files changed, 15 insertions(+), 1 deletion(-)



diff --git a/drivers/bluetooth/btbcm.c b/drivers/bluetooth/btbcm.c

index e4182acee488..4ecc50d93107 100644

--- a/drivers/bluetooth/btbcm.c

+++ b/drivers/bluetooth/btbcm.c

@@ -353,6 +353,10 @@ static int btbcm_read_info(struct hci_dev *hdev)

 		return PTR_ERR(skb);



 	bt_dev_info(hdev, "BCM: chip id %u", skb->data[1]);

+

+	if (skb->data[1] == 150)

+		set_bit(HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER, &hdev->quirks);

+

 	kfree_skb(skb);



 	/* Read Controller Features */

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

index b80415011dcd..9ce46cb8564d 100644

--- a/include/net/bluetooth/hci.h

+++ b/include/net/bluetooth/hci.h

@@ -246,6 +246,15 @@ enum {

 	 * HCI after resume.

 	 */

 	HCI_QUIRK_NO_SUSPEND_NOTIFIER,

+

+	/*

+	 * When this quirk is set, LE tx power is not queried on startup

+	 * and the min/max tx power values default to HCI_TX_POWER_INVALID.

+	 *

+	 * This quirk can be set before hci_register_dev is called or

+	 * during the hdev->setup vendor callback.

+	 */

+	HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER,

 };



 /* HCI device flags */

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c

index 8a47a3017d61..9a23fe7c8d67 100644

--- a/net/bluetooth/hci_core.c

+++ b/net/bluetooth/hci_core.c

@@ -742,7 +742,8 @@ static int hci_init3_req(struct hci_request *req, unsigned long opt)

 			hci_req_add(req, HCI_OP_LE_READ_ADV_TX_POWER, 0, NULL);

 		}



-		if (hdev->commands[38] & 0x80) {

+		if (hdev->commands[38] & 0x80 &&

+	    	!test_bit(HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER, &hdev->quirks)) {

 			/* Read LE Min/Max Tx Power*/

 			hci_req_add(req, HCI_OP_LE_READ_TRANSMIT_POWER,

 				    0, NULL);

--

2.33.0