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linux-next/drivers/char/snsc.c
David Howells 7d12e780e0 IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 
Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.

The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around.  On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).

Where appropriate, an arch may override the generic storage facility and do
something different with the variable.  On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.

Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions.  Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller.  A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.

I've build this code with allyesconfig for x86_64 and i386.  I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.

This will affect all archs.  Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:

	struct pt_regs *old_regs = set_irq_regs(regs);

And put the old one back at the end:

	set_irq_regs(old_regs);

Don't pass regs through to generic_handle_irq() or __do_IRQ().

In timer_interrupt(), this sort of change will be necessary:

	-	update_process_times(user_mode(regs));
	-	profile_tick(CPU_PROFILING, regs);
	+	update_process_times(user_mode(get_irq_regs()));
	+	profile_tick(CPU_PROFILING);

I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().

Some notes on the interrupt handling in the drivers:

 (*) input_dev() is now gone entirely.  The regs pointer is no longer stored in
     the input_dev struct.

 (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking.  It does
     something different depending on whether it's been supplied with a regs
     pointer or not.

 (*) Various IRQ handler function pointers have been moved to type
     irq_handler_t.

Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
2006-10-05 15:10:12 +01:00

462 lines
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/*
* SN Platform system controller communication support
*
* 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, 2006 Silicon Graphics, Inc. All rights reserved.
*/
/*
* System controller communication driver
*
* This driver allows a user process to communicate with the system
* controller (a.k.a. "IRouter") network in an SGI SN system.
*/
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/device.h>
#include <linux/poll.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/sn/io.h>
#include <asm/sn/sn_sal.h>
#include <asm/sn/module.h>
#include <asm/sn/geo.h>
#include <asm/sn/nodepda.h>
#include "snsc.h"
#define SYSCTL_BASENAME "snsc"
#define SCDRV_BUFSZ 2048
#define SCDRV_TIMEOUT 1000
static irqreturn_t
scdrv_interrupt(int irq, void *subch_data)
{
struct subch_data_s *sd = subch_data;
unsigned long flags;
int status;
spin_lock_irqsave(&sd->sd_rlock, flags);
spin_lock(&sd->sd_wlock);
status = ia64_sn_irtr_intr(sd->sd_nasid, sd->sd_subch);
if (status > 0) {
if (status & SAL_IROUTER_INTR_RECV) {
wake_up(&sd->sd_rq);
}
if (status & SAL_IROUTER_INTR_XMIT) {
ia64_sn_irtr_intr_disable
(sd->sd_nasid, sd->sd_subch,
SAL_IROUTER_INTR_XMIT);
wake_up(&sd->sd_wq);
}
}
spin_unlock(&sd->sd_wlock);
spin_unlock_irqrestore(&sd->sd_rlock, flags);
return IRQ_HANDLED;
}
/*
* scdrv_open
*
* Reserve a subchannel for system controller communication.
*/
static int
scdrv_open(struct inode *inode, struct file *file)
{
struct sysctl_data_s *scd;
struct subch_data_s *sd;
int rv;
/* look up device info for this device file */
scd = container_of(inode->i_cdev, struct sysctl_data_s, scd_cdev);
/* allocate memory for subchannel data */
sd = kzalloc(sizeof (struct subch_data_s), GFP_KERNEL);
if (sd == NULL) {
printk("%s: couldn't allocate subchannel data\n",
__FUNCTION__);
return -ENOMEM;
}
/* initialize subch_data_s fields */
sd->sd_nasid = scd->scd_nasid;
sd->sd_subch = ia64_sn_irtr_open(scd->scd_nasid);
if (sd->sd_subch < 0) {
kfree(sd);
printk("%s: couldn't allocate subchannel\n", __FUNCTION__);
return -EBUSY;
}
spin_lock_init(&sd->sd_rlock);
spin_lock_init(&sd->sd_wlock);
init_waitqueue_head(&sd->sd_rq);
init_waitqueue_head(&sd->sd_wq);
sema_init(&sd->sd_rbs, 1);
sema_init(&sd->sd_wbs, 1);
file->private_data = sd;
/* hook this subchannel up to the system controller interrupt */
rv = request_irq(SGI_UART_VECTOR, scdrv_interrupt,
IRQF_SHARED | IRQF_DISABLED,
SYSCTL_BASENAME, sd);
if (rv) {
ia64_sn_irtr_close(sd->sd_nasid, sd->sd_subch);
kfree(sd);
printk("%s: irq request failed (%d)\n", __FUNCTION__, rv);
return -EBUSY;
}
return 0;
}
/*
* scdrv_release
*
* Release a previously-reserved subchannel.
*/
static int
scdrv_release(struct inode *inode, struct file *file)
{
struct subch_data_s *sd = (struct subch_data_s *) file->private_data;
int rv;
/* free the interrupt */
free_irq(SGI_UART_VECTOR, sd);
/* ask SAL to close the subchannel */
rv = ia64_sn_irtr_close(sd->sd_nasid, sd->sd_subch);
kfree(sd);
return rv;
}
/*
* scdrv_read
*
* Called to read bytes from the open IRouter pipe.
*
*/
static inline int
read_status_check(struct subch_data_s *sd, int *len)
{
return ia64_sn_irtr_recv(sd->sd_nasid, sd->sd_subch, sd->sd_rb, len);
}
static ssize_t
scdrv_read(struct file *file, char __user *buf, size_t count, loff_t *f_pos)
{
int status;
int len;
unsigned long flags;
struct subch_data_s *sd = (struct subch_data_s *) file->private_data;
/* try to get control of the read buffer */
if (down_trylock(&sd->sd_rbs)) {
/* somebody else has it now;
* if we're non-blocking, then exit...
*/
if (file->f_flags & O_NONBLOCK) {
return -EAGAIN;
}
/* ...or if we want to block, then do so here */
if (down_interruptible(&sd->sd_rbs)) {
/* something went wrong with wait */
return -ERESTARTSYS;
}
}
/* anything to read? */
len = CHUNKSIZE;
spin_lock_irqsave(&sd->sd_rlock, flags);
status = read_status_check(sd, &len);
/* if not, and we're blocking I/O, loop */
while (status < 0) {
DECLARE_WAITQUEUE(wait, current);
if (file->f_flags & O_NONBLOCK) {
spin_unlock_irqrestore(&sd->sd_rlock, flags);
up(&sd->sd_rbs);
return -EAGAIN;
}
len = CHUNKSIZE;
set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(&sd->sd_rq, &wait);
spin_unlock_irqrestore(&sd->sd_rlock, flags);
schedule_timeout(SCDRV_TIMEOUT);
remove_wait_queue(&sd->sd_rq, &wait);
if (signal_pending(current)) {
/* wait was interrupted */
up(&sd->sd_rbs);
return -ERESTARTSYS;
}
spin_lock_irqsave(&sd->sd_rlock, flags);
status = read_status_check(sd, &len);
}
spin_unlock_irqrestore(&sd->sd_rlock, flags);
if (len > 0) {
/* we read something in the last read_status_check(); copy
* it out to user space
*/
if (count < len) {
pr_debug("%s: only accepting %d of %d bytes\n",
__FUNCTION__, (int) count, len);
}
len = min((int) count, len);
if (copy_to_user(buf, sd->sd_rb, len))
len = -EFAULT;
}
/* release the read buffer and wake anyone who might be
* waiting for it
*/
up(&sd->sd_rbs);
/* return the number of characters read in */
return len;
}
/*
* scdrv_write
*
* Writes a chunk of an IRouter packet (or other system controller data)
* to the system controller.
*
*/
static inline int
write_status_check(struct subch_data_s *sd, int count)
{
return ia64_sn_irtr_send(sd->sd_nasid, sd->sd_subch, sd->sd_wb, count);
}
static ssize_t
scdrv_write(struct file *file, const char __user *buf,
size_t count, loff_t *f_pos)
{
unsigned long flags;
int status;
struct subch_data_s *sd = (struct subch_data_s *) file->private_data;
/* try to get control of the write buffer */
if (down_trylock(&sd->sd_wbs)) {
/* somebody else has it now;
* if we're non-blocking, then exit...
*/
if (file->f_flags & O_NONBLOCK) {
return -EAGAIN;
}
/* ...or if we want to block, then do so here */
if (down_interruptible(&sd->sd_wbs)) {
/* something went wrong with wait */
return -ERESTARTSYS;
}
}
count = min((int) count, CHUNKSIZE);
if (copy_from_user(sd->sd_wb, buf, count)) {
up(&sd->sd_wbs);
return -EFAULT;
}
/* try to send the buffer */
spin_lock_irqsave(&sd->sd_wlock, flags);
status = write_status_check(sd, count);
/* if we failed, and we want to block, then loop */
while (status <= 0) {
DECLARE_WAITQUEUE(wait, current);
if (file->f_flags & O_NONBLOCK) {
spin_unlock(&sd->sd_wlock);
up(&sd->sd_wbs);
return -EAGAIN;
}
set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(&sd->sd_wq, &wait);
spin_unlock_irqrestore(&sd->sd_wlock, flags);
schedule_timeout(SCDRV_TIMEOUT);
remove_wait_queue(&sd->sd_wq, &wait);
if (signal_pending(current)) {
/* wait was interrupted */
up(&sd->sd_wbs);
return -ERESTARTSYS;
}
spin_lock_irqsave(&sd->sd_wlock, flags);
status = write_status_check(sd, count);
}
spin_unlock_irqrestore(&sd->sd_wlock, flags);
/* release the write buffer and wake anyone who's waiting for it */
up(&sd->sd_wbs);
/* return the number of characters accepted (should be the complete
* "chunk" as requested)
*/
if ((status >= 0) && (status < count)) {
pr_debug("Didn't accept the full chunk; %d of %d\n",
status, (int) count);
}
return status;
}
static unsigned int
scdrv_poll(struct file *file, struct poll_table_struct *wait)
{
unsigned int mask = 0;
int status = 0;
struct subch_data_s *sd = (struct subch_data_s *) file->private_data;
unsigned long flags;
poll_wait(file, &sd->sd_rq, wait);
poll_wait(file, &sd->sd_wq, wait);
spin_lock_irqsave(&sd->sd_rlock, flags);
spin_lock(&sd->sd_wlock);
status = ia64_sn_irtr_intr(sd->sd_nasid, sd->sd_subch);
spin_unlock(&sd->sd_wlock);
spin_unlock_irqrestore(&sd->sd_rlock, flags);
if (status > 0) {
if (status & SAL_IROUTER_INTR_RECV) {
mask |= POLLIN | POLLRDNORM;
}
if (status & SAL_IROUTER_INTR_XMIT) {
mask |= POLLOUT | POLLWRNORM;
}
}
return mask;
}
static const struct file_operations scdrv_fops = {
.owner = THIS_MODULE,
.read = scdrv_read,
.write = scdrv_write,
.poll = scdrv_poll,
.open = scdrv_open,
.release = scdrv_release,
};
static struct class *snsc_class;
/*
* scdrv_init
*
* Called at boot time to initialize the system controller communication
* facility.
*/
int __init
scdrv_init(void)
{
geoid_t geoid;
cnodeid_t cnode;
char devname[32];
char *devnamep;
struct sysctl_data_s *scd;
void *salbuf;
dev_t first_dev, dev;
nasid_t event_nasid;
if (!ia64_platform_is("sn2"))
return -ENODEV;
event_nasid = ia64_sn_get_console_nasid();
if (alloc_chrdev_region(&first_dev, 0, num_cnodes,
SYSCTL_BASENAME) < 0) {
printk("%s: failed to register SN system controller device\n",
__FUNCTION__);
return -ENODEV;
}
snsc_class = class_create(THIS_MODULE, SYSCTL_BASENAME);
for (cnode = 0; cnode < num_cnodes; cnode++) {
geoid = cnodeid_get_geoid(cnode);
devnamep = devname;
format_module_id(devnamep, geo_module(geoid),
MODULE_FORMAT_BRIEF);
devnamep = devname + strlen(devname);
sprintf(devnamep, "^%d#%d", geo_slot(geoid),
geo_slab(geoid));
/* allocate sysctl device data */
scd = kzalloc(sizeof (struct sysctl_data_s),
GFP_KERNEL);
if (!scd) {
printk("%s: failed to allocate device info"
"for %s/%s\n", __FUNCTION__,
SYSCTL_BASENAME, devname);
continue;
}
/* initialize sysctl device data fields */
scd->scd_nasid = cnodeid_to_nasid(cnode);
if (!(salbuf = kmalloc(SCDRV_BUFSZ, GFP_KERNEL))) {
printk("%s: failed to allocate driver buffer"
"(%s%s)\n", __FUNCTION__,
SYSCTL_BASENAME, devname);
kfree(scd);
continue;
}
if (ia64_sn_irtr_init(scd->scd_nasid, salbuf,
SCDRV_BUFSZ) < 0) {
printk
("%s: failed to initialize SAL for"
" system controller communication"
" (%s/%s): outdated PROM?\n",
__FUNCTION__, SYSCTL_BASENAME, devname);
kfree(scd);
kfree(salbuf);
continue;
}
dev = first_dev + cnode;
cdev_init(&scd->scd_cdev, &scdrv_fops);
if (cdev_add(&scd->scd_cdev, dev, 1)) {
printk("%s: failed to register system"
" controller device (%s%s)\n",
__FUNCTION__, SYSCTL_BASENAME, devname);
kfree(scd);
kfree(salbuf);
continue;
}
class_device_create(snsc_class, NULL, dev, NULL,
"%s", devname);
ia64_sn_irtr_intr_enable(scd->scd_nasid,
0 /*ignored */ ,
SAL_IROUTER_INTR_RECV);
/* on the console nasid, prepare to receive
* system controller environmental events
*/
if(scd->scd_nasid == event_nasid) {
scdrv_event_init(scd);
}
}
return 0;
}
module_init(scdrv_init);
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