lkml.org 
[lkml]   [2009]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] serial_core: avoid Break bouncing
From: Eran Liberty <liberty@extricom.com>

On some boxes, Break signal bounces, causing sysrq code to fail with some
serial interfaces.

A solution were posted on LKML in 2008:
http://lkml.indiana.edu/hypermail/linux/kernel/0809.2/0730.html

However, the fix weren't applied upstream.

This bug keeps happening, as shown at:
https://bugzilla.redhat.com/show_bug.cgi?id=518120

The original patch from Eran adds a debouncing logic that avoids that
multiple breaks to be badly handled by the serial code.

[mchehab@redhat.com: port the patch upstream and fix CodingStyle]

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index db532ce..765e169 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -443,8 +443,8 @@ static inline int
uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)
{
#ifdef SUPPORT_SYSRQ
- if (port->sysrq) {
- if (ch && time_before(jiffies, port->sysrq)) {
+ if (port->sysrq && time_after(jiffies, port->sysrq + HZ / 50)) {
+ if (ch && time_before(jiffies, port->sysrq + HZ * 5)) {
handle_sysrq(ch, port->state->port.tty);
port->sysrq = 0;
return 1;
@@ -464,18 +464,17 @@ uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)
static inline int uart_handle_break(struct uart_port *port)
{
struct uart_state *state = port->state;
+ int ret = 0;
+
#ifdef SUPPORT_SYSRQ
if (port->cons && port->cons->index == port->line) {
- if (!port->sysrq) {
- port->sysrq = jiffies + HZ*5;
- return 1;
- }
- port->sysrq = 0;
+ port->sysrq = jiffies;
+ ret = 1;
}
#endif
if (port->flags & UPF_SAK)
do_SAK(state->port.tty);
- return 0;
+ return ret;
}

/**


\
 
 \ /
  Last update: 2009-11-12 17:09    [W:0.092 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site