linux-kernel - [PATCH 3.12 03/56] USB: serial: cp210x: Removing unncessary `usb_reset

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Message-Id: <664dc48e6aaa67b14a4742d1bf77bde15b1603e6.1409735865.git.jslaby@suse.cz>
Date:	Wed,  3 Sep 2014 11:26:22 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Preston Fick <preston.fick@...abs.com>,
	Johan Hovold <johan@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 03/56] USB: serial: cp210x: Removing unncessary `usb_reset_device` on startup

From: Preston Fick <preston.fick@...abs.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 934ef5aca9daea10507eebcbd0fb8f6d57d55359 upstream.

This `usb_reset_device` command has been around since the driver was
originally reverse engineered. It doesn't cause much issue on single
interface CP210x devices, but on the CP2105 and CP2108 with 2 and 4
interfaces respectively it will cause instability on enumeration and
delays enumeration noticably. There should be no reason to reset a device
at startup, per the CP210x AN571 spec.

Signed-off-by: Preston Fick <preston.fick@...abs.com>
Cc: Johan Hovold <johan@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/usb/serial/cp210x.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index 1db213a6e843..e5ac744ac73f 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -860,9 +860,6 @@ static int cp210x_startup(struct usb_serial *serial)
 	struct usb_host_interface *cur_altsetting;
 	struct cp210x_serial_private *spriv;
 
-	/* cp210x buffers behave strangely unless device is reset */
-	usb_reset_device(serial->dev);
-
 	spriv = kzalloc(sizeof(*spriv), GFP_KERNEL);
 	if (!spriv)
 		return -ENOMEM;
-- 
2.1.0

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