linux-kernel - [PATCH 1/1] Removing unncessary `usb_reset

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Message-Id: <1405539090-5682-1-git-send-email-pffick@gmail.com>
Date:	Wed, 16 Jul 2014 14:31:30 -0500
From:	Preston Fick <pffick@...il.com>
To:	jhovold@...il.com, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	preston.fick@...abs.com
Subject: [PATCH 1/1] Removing unncessary `usb_reset_device` on startup

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

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>
---
 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 762e4a5..6891269 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -855,9 +855,6 @@ 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;
-- 
1.9.1

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