From: Alan Cox <alan@linux.intel.com>
Date: Thu, 9 Jul 2009 12:35:52 +0000 (+0100)
Subject: tty: Sort out the USB sysrq changes that wrecked performance
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=4cd1de0afaaa45309f34d7282ea4c07d9b56a3ff;p=openwrt%2Fstaging%2Fblogic.git

tty: Sort out the USB sysrq changes that wrecked performance

We can't go around calling all sorts of magic per character functions at
full rate 3G data speed.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 932d6241b787..3d8dc5671bea 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -424,10 +424,17 @@ static void flush_and_resubmit_read_urb(struct usb_serial_port *port)
 	if (!tty)
 		goto done;
 
-	/* Push data to tty */
-	for (i = 0; i < urb->actual_length; i++, ch++) {
-		if (!usb_serial_handle_sysrq_char(port, *ch))
-			tty_insert_flip_char(tty, *ch, TTY_NORMAL);
+	/* The per character mucking around with sysrq path it too slow for
+	   stuff like 3G modems, so shortcircuit it in the 99.9999999% of cases
+	   where the USB serial is not a console anyway */
+	if (!port->console || !port->sysrq)
+		tty_insert_flip_string(tty, ch, urb->actual_length);
+	else {
+		/* Push data to tty */
+		for (i = 0; i < urb->actual_length; i++, ch++) {
+			if (!usb_serial_handle_sysrq_char(port, *ch))
+				tty_insert_flip_char(tty, *ch, TTY_NORMAL);
+		}
 	}
 	tty_flip_buffer_push(tty);
 	tty_kref_put(tty);