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From:   Douglas Anderson <dianders@chromium.org>
To:     Jakub Kicinski <kuba@kernel.org>,
        Hayes Wang <hayeswang@realtek.com>,
        "David S . Miller" <davem@davemloft.net>
Cc:     Grant Grundler <grundler@chromium.org>,
        Edward Hill <ecgh@chromium.org>, linux-usb@vger.kernel.org,
        Simon Horman <horms@kernel.org>,
        Laura Nao <laura.nao@collabora.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Douglas Anderson <dianders@chromium.org>,
        =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn@mork.no>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org
Subject: [PATCH v4 1/5] r8152: Increase USB control msg timeout to 5000ms as per spec
Date:   Thu, 19 Oct 2023 14:20:20 -0700
Message-ID: <20231019142019.v4.1.I6e4fb5ae61b4c6ab32058cb12228fd5bd32da676@changeid>
In-Reply-To: <20231019212130.3146151-1-dianders@chromium.org>
References: <20231019212130.3146151-1-dianders@chromium.org>
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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>
---

(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