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References: <20231020210751.3415723-1-dianders@chromium.org> <20231020140655.v5.1.I6e4fb5ae61b4c6ab32058cb12228fd5bd32da676@changeid>
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From:   Grant Grundler <grundler@chromium.org>
Date:   Sat, 21 Oct 2023 07:48:59 -0700
Message-ID: <CANEJEGt4HwnPDyO=R0uRju5NtZDfXYd1G0_Tzu7ioNcFVz7cZA@mail.gmail.com>
Subject: Re: [PATCH v5 1/8] r8152: Increase USB control msg timeout to 5000ms
 as per spec
To:     Douglas Anderson <dianders@chromium.org>
Cc:     Jakub Kicinski <kuba@kernel.org>,
        Hayes Wang <hayeswang@realtek.com>,
        "David S . Miller" <davem@davemloft.net>,
        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
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On Fri, Oct 20, 2023 at 2:08=E2=80=AFPM Douglas Anderson <dianders@chromium=
.org> 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: Grant Grundler <grundler@chromium.org>

> ---
>
> (no changes since v1)
>
>  drivers/net/usb/r8152.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index 0c13d9950cd8..482957beae66 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -1212,7 +1212,7 @@ int get_registers(struct r8152 *tp, u16 value, u16 =
index, u16 size, void *data)
>
>         ret =3D usb_control_msg(tp->udev, tp->pipe_ctrl_in,
>                               RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
> -                             value, index, tmp, size, 500);
> +                             value, index, tmp, size, USB_CTRL_GET_TIMEO=
UT);
>         if (ret < 0)
>                 memset(data, 0xff, size);
>         else
> @@ -1235,7 +1235,7 @@ int set_registers(struct r8152 *tp, u16 value, u16 =
index, u16 size, void *data)
>
>         ret =3D usb_control_msg(tp->udev, tp->pipe_ctrl_out,
>                               RTL8152_REQ_SET_REGS, RTL8152_REQT_WRITE,
> -                             value, index, tmp, size, 500);
> +                             value, index, tmp, size, USB_CTRL_SET_TIMEO=
UT);
>
>         kfree(tmp);
>
> @@ -9494,7 +9494,8 @@ static u8 __rtl_get_hw_ver(struct usb_device *udev)
>
>         ret =3D usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
>                               RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
> -                             PLA_TCR0, MCU_TYPE_PLA, tmp, sizeof(*tmp), =
500);
> +                             PLA_TCR0, MCU_TYPE_PLA, tmp, sizeof(*tmp),
> +                             USB_CTRL_GET_TIMEOUT);
>         if (ret > 0)
>                 ocp_data =3D (__le32_to_cpu(*tmp) >> 16) & VERSION_MASK;
>
> --
> 2.42.0.758.gaed0368e0e-goog
>