linux-kernel - Re: [PATCH v3 2/2] Bluetooth: hci_qca: wcn3990: Drop baudrate change vendor event

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Message-ID: <20190521194600.GI40515@google.com>
Date:   Tue, 21 May 2019 12:46:00 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>
Cc:     linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
        Balakrishna Godavarthi <bgodavar@...eaurora.org>,
        Harish Bandi <c-hbandi@...eaurora.org>,
        Rocky Liao <rjliao@...eaurora.org>
Subject: Re: [PATCH v3 2/2] Bluetooth: hci_qca: wcn3990: Drop baudrate change
 vendor event

On Mon, Apr 29, 2019 at 04:21:31PM -0700, 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 is 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>
> ---

Harish Bandi <c-hbandi@...eaurora.org> privately reported to me that
he sees frame reassembly errors with this patch and WCN3998. He
didn't provide any more details yet, so at this point we only know
that there appears to be some difference between WCN3990 and WCN3998
wrt firmware download.

For now let's limit this fix to WCN3990. We can revisit WCN3998 later
if it is confirmed that it has the same problem.