path: root/drivers/misc/sgi-xp/xpc_main.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2004-2008 Silicon Graphics, Inc.  All Rights Reserved.
 */

/*
 * Cross Partition Communication (XPC) support - standard version.
 *
 *	XPC provides a message passing capability that crosses partition
 *	boundaries. This module is made up of two parts:
 *
 *	    partition	This part detects the presence/absence of other
 *			partitions. It provides a heartbeat and monitors
 *			the heartbeats of other partitions.
 *
 *	    channel	This part manages the channels and sends/receives
 *			messages across them to/from other partitions.
 *
 *	There are a couple of additional functions residing in XP, which
 *	provide an interface to XPC for its users.
 *
 *
 *	Caveats:
 *
 *	  . We currently have no way to determine which nasid an IPI came
 *	    from. Thus, xpc_IPI_send() does a remote AMO write followed by
 *	    an IPI. The AMO indicates where data is to be pulled from, so
 *	    after the IPI arrives, the remote partition checks the AMO word.
 *	    The IPI can actually arrive before the AMO however, so other code
 *	    must periodically check for this case. Also, remote AMO operations
 *	    do not reliably time out. Thus we do a remote PIO read solely to
 *	    know whether the remote partition is down and whether we should
 *	    stop sending IPIs to it. This remote PIO read operation is set up
 *	    in a special nofault region so SAL knows to ignore (and cleanup)
 *	    any errors due to the remote AMO write, PIO read, and/or PIO
 *	    write operations.
 *
 *	    If/when new hardware solves this IPI problem, we should abandon
 *	    the current approach.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/completion.h>
#include <linux/kdebug.h>
#include <linux/kthread.h>
#include <linux/uaccess.h>
#include <asm/sn/intr.h>
#include <asm/sn/sn_sal.h>
#include "xpc.h"

/* define two XPC debug device structures to be used with dev_dbg() et al */

struct device_driver xpc_dbg_name = {
	.name = "xpc"
};

struct device xpc_part_dbg_subname = {
	.bus_id = {0},		/* set to "part" at xpc_init() time */
	.driver = &xpc_dbg_name
};

struct device xpc_chan_dbg_subname = {
	.bus_id = {0},		/* set to "chan" at xpc_init() time */
	.driver = &xpc_dbg_name
};

struct device *xpc_part = &xpc_part_dbg_subname;
struct device *xpc_chan = &xpc_chan_dbg_subname;

static int xpc_kdebug_ignore;

/* systune related variables for /proc/sys directories */

static int xpc_hb_interval = XPC_HB_DEFAULT_INTERVAL;
static int xpc_hb_min_interval = 1;
static int xpc_hb_max_interval = 10;

static int xpc_hb_check_interval = XPC_HB_CHECK_DEFAULT_INTERVAL;
static int xpc_hb_check_min_interval = 10;
static int xpc_hb_check_max_interval = 120;

int xpc_disengage_request_timelimit = XPC_DISENGAGE_REQUEST_DEFAULT_TIMELIMIT;
static int xpc_disengage_request_min_timelimit;	/* = 0 */
static int xpc_disengage_request_max_timelimit = 120;

static ctl_table xpc_sys_xpc_hb_dir[] = {
	{
	 .ctl_name = CTL_UNNUMBERED,
	 .procname = "hb_interval",
	 .data = &xpc_hb_interval,
	 .maxlen = sizeof(int),
	 .mode = 0644,
	 .proc_handler = &proc_dointvec_minmax,
	 .strategy = &sysctl_intvec,