linux-kernel - Re: [PATCH] mwifiex: Ignore BTCOEX events from the 88W8897 firmware

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Message-ID: <20211129233209.GA2702252@bhelgaas>
Date:   Mon, 29 Nov 2021 17:32:09 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jonas Dreßler <verdre@...d.nl>
Cc:     Amitkumar Karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi017@...il.com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Tsuchiya Yuto <kitakar@...il.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Maximilian Luz <luzmaximilian@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Pali Rohár <pali@...nel.org>
Subject: Re: [PATCH] mwifiex: Ignore BTCOEX events from the 88W8897 firmware

On Wed, Nov 03, 2021 at 09:58:27PM +0100, Jonas Dreßler wrote:
> The firmware of the 88W8897 PCIe+USB card sends those events very
> unreliably, sometimes bluetooth together with 2.4ghz-wifi is used and no
> COEX event comes in, and sometimes bluetooth is disabled but the
> coexistance mode doesn't get disabled.

s/sends those events/sends BTCOEX events/ so it reads well without the
subject.

s/coexistance/coexistence/

Is BTCOEX a standard Bluetooth thing?  Is there a spec reference that
could be useful here?  I've never seen those specs, so this is just
curiosity.  I did download the "Bluetooth Core Spec v5.3", which does
have a "Wireless Coexistence Signaling and Interfaces" chapter, but
"BTCOEX" doesn't appear in that doc.

> This means we sometimes end up capping the rx/tx window size while
> bluetooth is not enabled anymore, artifically limiting wifi speeds even
> though bluetooth is not being used.

s/artifically/artificially/

> Since we can't fix the firmware, let's just ignore those events on the
> 88W8897 device. From some Wireshark capture sessions it seems that the
> Windows driver also doesn't change the rx/tx window sizes when bluetooth
> gets enabled or disabled, so this is fairly consistent with the Windows
> driver.