linux-kernel - Re: [PATCH 2/2] Bluetooth: hci_qca: wcn3990: Drop baudrate change vendor event

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Message-ID: <c985a6712f91930d7c710ca4abb42e80@codeaurora.org>
Date:   Mon, 01 Apr 2019 13:29:43 +0530
From:   Balakrishna Godavarthi <bgodavar@...eaurora.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hemantg <hemantg@...eaurora.org>
Subject: Re: [PATCH 2/2] Bluetooth: hci_qca: wcn3990: Drop baudrate change
 vendor event

Hi Matthias,

Sorry for the late reply i was on vacation.

On 2019-03-08 05:00, Matthias Kaehlcke wrote:
> On Thu, Mar 07, 2019 at 10:20:09AM -0800, Matthias Kaehlcke wrote:
>> Hi Balakrishna,
>> 
>> On Thu, Mar 07, 2019 at 10:35:08AM +0530, Balakrishna Godavarthi 
>> wrote:
>> > hi Matthias,
>> >
>> > On 2019-03-07 06:10, Matthias Kaehlcke wrote:
>> > > Firmware download to the WCN3990 often fails with a 'TLV response size
>> > > mismatch' error:
>> > >
>> > > [  133.064659] Bluetooth: hci0: setting up wcn3990
>> > > [  133.489150] Bluetooth: hci0: QCA controller version 0x02140201
>> > > [  133.495245] Bluetooth: hci0: QCA Downloading qca/crbtfw21.tlv
>> > > [  133.507214] Bluetooth: hci0: QCA TLV response size mismatch
>> > > [  133.513265] Bluetooth: hci0: QCA Failed to download patch (-84)
>> > >
>> > > This is caused by a vendor event that corresponds to an earlier command
>> > > to change the baudrate. The event is not processed in the context of the
>> > > baudrate change and later interpreted as response to the firmware
>> > > download command (which is also a vendor command), but the driver
>> > > detects
>> > > that the event doesn't have the expected amount of associated data.
>> > >
>> > > More details:
>> > >
>> > > For the WCN3990 the vendor command for a baudrate change isn't sent as
>> > > synchronous HCI command, because the controller sends the corresponding
>> > > vendor event with the new baudrate. The event is received and decoded
>> > > after the baudrate change of the host port.
>> > >
>> > > Identify the 'unused' event when it is received and don't add it to
>> > > the queue of RX frames.
>> > >
>> > > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
>> > > ---
>> >
>> > ...
>> >
>> > Can you test by reverting this change "94d6671473924".
>> 
>> The issue is still reproducible.
>> 
>> > We need at least 15ms minimum delay for the soc to change its baud rate and
>> > respond to the with command complete event.
>> 
>> The baudrate change has clearly been successful when the problem is
>> observed, since the host receives the vendor event with the new
>> baudrate.
> 
> I forgot to mention this earlier: the controller doesn't send a
> command complete event for the command, or at least not a correct
> one.
> 
> That's the data that is received:
> 
> 04 0e 04 01 00 00 00
>             ~~ ~~
> 
[Bala]: can you share me the command sent and event recevied.
  I see that we receive a command complete event for the baud rate change 
command.

command sent: 01 48 fc 01 11
vendor specific event: 04 ff 02 92 01
command complete event: 04 0e 04 01 00 00 00.



> This is *a* command complete event, but the opcode is 0x0000 instead
> of the earlier command. The same happens for the firmware
> download/read version command, which is the reason why the command
> complete injection mess
> (https://lore.kernel.org/patchwork/patch/1027955/) is needed in one
> way or another.
> 
[Bala]: fw download approach is different where we use __hci_cmd_sync() 
where as here we use hci_uart_tx_wakeup()
         which directly calls the hci_uart_write_work(). so even we send 
an valid opcode or not for baudrate change will bot matter.

> I wished Qualcomm FW developers would get their act together and:
> 
> - send actual command complete events :
> - acknowledge a baudrate change request using the current baudrate
>   like Broadcom and Intel chips apparently do
> 
> this would have saved countless hours of debugging and implementing
> quirky workarounds ...
> 
> Maybe there is hope for future chips (hint, hint)?

[Bala]: will take this forward to the SoC teams.

-- 
Regards
Balakrishna.