Re: [PATCHv2] Bluetooth: quirk disabling LE Read Transmit Power

[Aditya Garg]

> On 06-Nov-2021, at 3:17 AM, Luiz Augusto von Dentz <luiz.dentz@xxxxxxxxx> wrote:
> 
> Hi Orlando,
> 
> On Fri, Oct 1, 2021 at 1:56 AM Orlando Chamberlain
> <redecorating@xxxxxxxxxxxxxx> wrote:
>> 
>> 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@xxxxxxxxxxxxxx
>> Signed-off-by: Orlando Chamberlain <redecorating@xxxxxxxxxxxxxx>
>> ---
>> 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.
> 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
>