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Message-ID: <2f12beb1-ff94-4806-8ed7-e78eb8474a7d@gmail.com>
Date:   Mon, 23 Oct 2023 18:23:37 -0700
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Subject: Re: [PATCH v5 1/8] r8152: Increase USB control msg timeout to 5000ms
 as per spec
Content-Language: en-US
To:     Douglas Anderson <dianders@chromium.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Hayes Wang <hayeswang@realtek.com>,
        "David S . Miller" <davem@davemloft.net>
Cc:     Edward Hill <ecgh@chromium.org>,
        Laura Nao <laura.nao@collabora.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Simon Horman <horms@kernel.org>, linux-usb@vger.kernel.org,
        Grant Grundler <grundler@chromium.org>,
        =?UTF-8?Q?Bj=C3=B8rn_Mork?= <bjorn@mork.no>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org
References: <20231020210751.3415723-1-dianders@chromium.org>
 <20231020140655.v5.1.I6e4fb5ae61b4c6ab32058cb12228fd5bd32da676@changeid>
From:   Florian Fainelli <f.fainelli@gmail.com>
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In-Reply-To: <20231020140655.v5.1.I6e4fb5ae61b4c6ab32058cb12228fd5bd32da676@changeid>
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Precedence: bulk


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@realtek.com>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

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