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Date: Sat, 21 Oct 2023 07:48:59 -0700
From: Grant Grundler <grundler@...omium.org>
To: Douglas Anderson <dianders@...omium.org>
Cc: Jakub Kicinski <kuba@...nel.org>, Hayes Wang <hayeswang@...ltek.com>, 
	"David S . Miller" <davem@...emloft.net>, 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 Fri, Oct 20, 2023 at 2:08 PM Douglas Anderson <dianders@...omium.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@...ltek.com>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Grant Grundler <grundler@...omium.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 = 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_TIMEOUT);
>         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 = 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_TIMEOUT);
>
>         kfree(tmp);
>
> @@ -9494,7 +9494,8 @@ static u8 __rtl_get_hw_ver(struct usb_device *udev)
>
>         ret = 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 = (__le32_to_cpu(*tmp) >> 16) & VERSION_MASK;
>
> --
> 2.42.0.758.gaed0368e0e-goog
>

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