On 06-Nov-2021, at 3:17 AM, Luiz Augusto von Dentz [off-list ref] wrote:

Hi Orlando,

On Fri, Oct 1, 2021 at 1:56 AM Orlando Chamberlain
[off-list ref] wrote:

quoted

The LE Read Transmit Power command is Advertised on some Broadcom
controlers, but not supported. Using this command breaks Bluetooth
on the MacBookPro16,1 and iMac20,1. Added a quirk disabling LE Read
Transmit Power for these devices, based off their common chip id 150.

Link: https://lore.kernel.org/r/4970a940-211b-25d6-edab-21a815313954@protonmail.com (local)
Signed-off-by: Orlando Chamberlain <redacted>
---
v1->v2: Clarified quirk description

drivers/bluetooth/btbcm.c   |  4 ++++
include/net/bluetooth/hci.h | 11 +++++++++++
net/bluetooth/hci_core.c    |  3 ++-
3 files changed, 17 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..6da9bd6b7259 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h

@@ -246,6 +246,17 @@ enum {
        * HCI after resume.
        */
       HCI_QUIRK_NO_SUSPEND_NOTIFIER,
+
+       /* When this quirk is set, LE Read Transmit Power is disabled.
+        * This is mainly due to the fact that the HCI LE Read Transmit
+        * Power command is advertised, but not supported; these
+        * controllers often reply with unknown command and need a hard
+        * reset.
+        *
+        * 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

Nowadays it is possible to treat errors such like this on a per
command basis (assuming it is not essential for the init sequence):

diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 979da5179ff4..f244f42cc609 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h

@@ -551,6 +551,7 @@ enum {

#define HCI_LK_AUTH_COMBINATION_P256   0x08

/* ---- HCI Error Codes ---- */
+#define HCI_ERROR_UNKNOWN_CMD          0x01
#define HCI_ERROR_UNKNOWN_CONN_ID      0x02
#define HCI_ERROR_AUTH_FAILURE         0x05
#define HCI_ERROR_PIN_OR_KEY_MISSING   0x06

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

index bb88d31d2212..9c697e058974 100644

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

@@ -3325,11 +3325,18 @@ static int

hci_le_read_adv_tx_power_sync(struct hci_dev *hdev)
/* Read LE Min/Max Tx Power*/
static int hci_le_read_tx_power_sync(struct hci_dev *hdev)
{
+       int status;
+
       if (!(hdev->commands[38] & 0x80))
               return 0;

-       return __hci_cmd_sync_status(hdev, HCI_OP_LE_READ_TRANSMIT_POWER,
-                                    0, NULL, HCI_CMD_TIMEOUT);
+       status = __hci_cmd_sync_status(hdev, HCI_OP_LE_READ_TRANSMIT_POWER,
+                                      0, NULL, HCI_CMD_TIMEOUT);
+       /* Ignore if command is not really supported */
+       if (status == HCI_ERROR_UNKNOWN_CMD)
+               return 0;
+
+       return status;
}

/* Read LE Accept List Size */

Anyway, it would probably be worth pointing out to the vendor they
have a broken firmware if they do mark the command as supported but
return such error.

-- 
Luiz Augusto von Dentz