From 4cd1de0afaaa45309f34d7282ea4c07d9b56a3ff Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@linux.intel.com>
Date: Thu, 9 Jul 2009 13:35:52 +0100
Subject: [PATCH] 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>
---
drivers/usb/serial/generic.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
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);
--
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