linux-kernel - Re: [PATCH] Bluetooth: btqca: Add a short delay before downloading the NVM

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Message-Id: <21246F6F-ADF5-4D05-8690-D0ABD793BA64@holtmann.org>
Date:   Thu, 11 Jul 2019 09:06:45 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        Linux Bluetooth mailing list 
        <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] Bluetooth: btqca: Add a short delay before downloading
 the NVM

Hi Matthias,

> On WCN3990 downloading the NVM sometimes fails with a "TLV response
> size mismatch" error:
> 
> [  174.949955] Bluetooth: btqca.c:qca_download_firmware() hci0: QCA Downloading qca/crnv21.bin
> [  174.958718] Bluetooth: btqca.c:qca_tlv_send_segment() hci0: QCA TLV response size mismatch
> 
> It seems the controller needs a short time after downloading the
> firmware before it is ready for the NVM. A delay as short as 1 ms
> seems sufficient, make it 10 ms just in case. No event is received
> during the delay, hence we don't just silently drop an extra event.
> 
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> ---
> I'm only guessing why the delay is needed, maybe QCA folks can shed
> more light on this.
> 
> I didn't see this error when testing 2faa3f15fa2f ("Bluetooth: hci_qca:
> wcn3990: Drop baudrate change vendor event") and 32646db8cc28
> ("Bluetooth: btqca: inject command complete event during fw download")
> intensively a few months ago. My guess is that some changes in the kernel
> (I test with a 4.19 kernel with regular -stable merges) altered the
> timing, which made this issue visible.
> ---
> drivers/bluetooth/btqca.c | 3 +++
> 1 file changed, 3 insertions(+)

patch has been applied to bluetooth-next tree.

Regards

Marcel