linux-kernel - Re: [PATCH v5 1/8] r8152: Increase USB control msg timeout to 5000ms as per spec

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Message-ID: <2f12beb1-ff94-4806-8ed7-e78eb8474a7d@gmail.com>
Date:   Mon, 23 Oct 2023 18:23:37 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Douglas Anderson <dianders@...omium.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Hayes Wang <hayeswang@...ltek.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     Edward Hill <ecgh@...omium.org>,
        Laura Nao <laura.nao@...labora.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Simon Horman <horms@...nel.org>, linux-usb@...r.kernel.org,
        Grant Grundler <grundler@...omium.org>,
        Bjørn Mork <bjorn@...k.no>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v5 1/8] r8152: Increase USB control msg timeout to 5000ms
 as per spec



On 10/20/2023 2:06 PM, Douglas Anderson wrote:
> According to the comment next to USB_CTRL_GET_TIMEOUT and
> USB_CTRL_SET_TIMEOUT, although sending/receiving control messages is
> usually quite fast, the spec allows them to take up to 5 seconds.
> Let's increase the timeout in the Realtek driver from 500ms to 5000ms
> (using the #defines) to account for this.
> 
> This is not just a theoretical change. The need for the longer timeout
> was seen in testing. Specifically, if you drop a sc7180-trogdor based
> Chromebook into the kdb debugger and then "go" again after sitting in
> the debugger for a while, the next USB control message takes a long
> time. Out of ~40 tests the slowest USB control message was 4.5
> seconds.
> 
> While dropping into kdb is not exactly an end-user scenario, the above
> is similar to what could happen due to an temporary interrupt storm,
> what could happen if there was a host controller (HW or SW) issue, or
> what could happen if the Realtek device got into a confused state and
> needed time to recover.
> 
> This change is fairly critical since the r8152 driver in Linux doesn't
> expect register reads/writes (which are backed by USB control
> messages) to fail.
> 
> Fixes: ac718b69301c ("net/usb: new driver for RTL8152")
> Suggested-by: Hayes Wang <hayeswang@...ltek.com>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
-- 
Florian