Hi, this is your Linux kernel regression tracker speaking. To make this
easy and quick to read for everyone I for once rely on top-posting:

Bluetooth maintainers, what's the status here? The proposed patch is
fixing a regression. It's not a recent one (it afaics was introduced in
v5.11-rc1). Nevertheless it would be good to get this finally resolved.
But this thread seems inactive for more than a week now. Or was progress
made, but is only visible somewhere else?

Ciao, Thorsten (carrying his Linux kernel regression tracker hat)

P.S.: As a Linux kernel regression tracker I'm getting a lot of reports
on my table. I can only look briefly into most of them. Therefore I
unfortunately will get things wrong or miss something important. I hope
that's not the case here; if you think it is, don't hesitate to tell me
about it in a public reply. That's in everyone's interest, as what I
wrote above might be misleading to everyone reading this, which is
something I'd like to avoid.

BTW, I have no personal interest in this issue, which is tracked using
regzbot, my Linux kernel regression tracking bot
(https://linux-regtracking.leemhuis.info/regzbot/). I'm only posting
this mail to hopefully get things rolling again and hence don't need to
be CC on all further activities wrt to this regression. Also feel free
to ignore the following lines, they are meant for regzbot:

#regzbot poke

On 07.11.21 09:35, Greg KH wrote:

On Sat, Nov 06, 2021 at 05:27:27PM +0000, Aditya Garg wrote:

quoted

quoted

On 06-Nov-2021, at 5:19 PM, Greg KH [off-list ref] wrote:
On Sat, Nov 06, 2021 at 09:41:28AM +0000, Aditya Garg wrote:

quoted

quoted

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

This diff cannot be applied to stable 5.15. Could you provide a patch capable of being applied to stable.

That is not needed until a patch is in Linus's tree.  Why do you need it
earlier?

Well not an emergency, but the issue of Bluetooth not working on some Apple Macs has been there for a long time. BTW, will this patch be there in Linus’s tree in the coming days?

That is up to the bluetooth maintainers, they have to accept it first.

thanks,

greg k-h