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linux/drivers/i2c/busses/i2c-ite.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

278 lines
7.1 KiB
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/*
-------------------------------------------------------------------------
i2c-adap-ite.c i2c-hw access for the IIC peripheral on the ITE MIPS system
-------------------------------------------------------------------------
Hai-Pao Fan, MontaVista Software, Inc.
hpfan@mvista.com or source@mvista.com
Copyright 2001 MontaVista Software Inc.
----------------------------------------------------------------------------
This file was highly leveraged from i2c-elektor.c, which was created
by Simon G. Vogl and Hans Berglund:
Copyright (C) 1995-97 Simon G. Vogl
1998-99 Hans Berglund
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/* ------------------------------------------------------------------------- */
/* With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi> and even
Frodo Looijaard <frodol@dds.nl> */
#include <linux/kernel.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-ite.h>
#include <linux/i2c-adap-ite.h>
#include "../i2c-ite.h"
#define DEFAULT_BASE 0x14014030
#define ITE_IIC_IO_SIZE 0x40
#define DEFAULT_IRQ 0
#define DEFAULT_CLOCK 0x1b0e /* default 16MHz/(27+14) = 400KHz */
#define DEFAULT_OWN 0x55
static int base;
static int irq;
static int clock;
static int own;
static struct iic_ite gpi;
static wait_queue_head_t iic_wait;
static int iic_pending;
static spinlock_t lock;
/* ----- local functions ---------------------------------------------- */
static void iic_ite_setiic(void *data, int ctl, short val)
{
unsigned long j = jiffies + 10;
pr_debug(" Write 0x%02x to 0x%x\n",(unsigned short)val, ctl&0xff);
#ifdef DEBUG
while (time_before(jiffies, j))
schedule();
#endif
outw(val,ctl);
}
static short iic_ite_getiic(void *data, int ctl)
{
short val;
val = inw(ctl);
pr_debug("Read 0x%02x from 0x%x\n",(unsigned short)val, ctl&0xff);
return (val);
}
/* Return our slave address. This is the address
* put on the I2C bus when another master on the bus wants to address us
* as a slave
*/
static int iic_ite_getown(void *data)
{
return (gpi.iic_own);
}
static int iic_ite_getclock(void *data)
{
return (gpi.iic_clock);
}
/* Put this process to sleep. We will wake up when the
* IIC controller interrupts.
*/
static void iic_ite_waitforpin(void) {
DEFINE_WAIT(wait);
int timeout = 2;
unsigned long flags;
/* If interrupts are enabled (which they are), then put the process to
* sleep. This process will be awakened by two events -- either the
* the IIC peripheral interrupts or the timeout expires.
* If interrupts are not enabled then delay for a reasonable amount
* of time and return.
*/
if (gpi.iic_irq > 0) {
spin_lock_irqsave(&lock, flags);
if (iic_pending == 0) {
spin_unlock_irqrestore(&lock, flags);
prepare_to_wait(&iic_wait, &wait, TASK_INTERRUPTIBLE);
if (schedule_timeout(timeout*HZ)) {
spin_lock_irqsave(&lock, flags);
if (iic_pending == 1) {
iic_pending = 0;
}
spin_unlock_irqrestore(&lock, flags);
}
finish_wait(&iic_wait, &wait);
} else {
iic_pending = 0;
spin_unlock_irqrestore(&lock, flags);
}
} else {
udelay(100);
}
}
static irqreturn_t iic_ite_handler(int this_irq, void *dev_id)
{
spin_lock(&lock);
iic_pending = 1;
spin_unlock(&lock);
wake_up_interruptible(&iic_wait);
return IRQ_HANDLED;
}
/* Lock the region of memory where I/O registers exist. Request our
* interrupt line and register its associated handler.
*/
static int iic_hw_resrc_init(void)
{
if (!request_region(gpi.iic_base, ITE_IIC_IO_SIZE, "i2c"))
return -ENODEV;
if (gpi.iic_irq <= 0)
return 0;
if (request_irq(gpi.iic_irq, iic_ite_handler, 0, "ITE IIC", 0) < 0)
gpi.iic_irq = 0;
else
enable_irq(gpi.iic_irq);
return 0;
}
static void iic_ite_release(void)
{
if (gpi.iic_irq > 0) {
disable_irq(gpi.iic_irq);
free_irq(gpi.iic_irq, 0);
}
release_region(gpi.iic_base , 2);
}
/* ------------------------------------------------------------------------
* Encapsulate the above functions in the correct operations structure.
* This is only done when more than one hardware adapter is supported.
*/
static struct i2c_algo_iic_data iic_ite_data = {
NULL,
iic_ite_setiic,
iic_ite_getiic,
iic_ite_getown,
iic_ite_getclock,
iic_ite_waitforpin,
80, 80, 100, /* waits, timeout */
};
static struct i2c_adapter iic_ite_ops = {
.owner = THIS_MODULE,
.id = I2C_HW_I_IIC,
.algo_data = &iic_ite_data,
.name = "ITE IIC adapter",
};
/* Called when the module is loaded. This function starts the
* cascade of calls up through the hierarchy of i2c modules (i.e. up to the
* algorithm layer and into to the core layer)
*/
static int __init iic_ite_init(void)
{
struct iic_ite *piic = &gpi;
printk(KERN_INFO "Initialize ITE IIC adapter module\n");
if (base == 0)
piic->iic_base = DEFAULT_BASE;
else
piic->iic_base = base;
if (irq == 0)
piic->iic_irq = DEFAULT_IRQ;
else
piic->iic_irq = irq;
if (clock == 0)
piic->iic_clock = DEFAULT_CLOCK;
else
piic->iic_clock = clock;
if (own == 0)
piic->iic_own = DEFAULT_OWN;
else
piic->iic_own = own;
iic_ite_data.data = (void *)piic;
init_waitqueue_head(&iic_wait);
spin_lock_init(&lock);
if (iic_hw_resrc_init() == 0) {
if (i2c_iic_add_bus(&iic_ite_ops) < 0)
return -ENODEV;
} else {
return -ENODEV;
}
printk(KERN_INFO " found device at %#x irq %d.\n",
piic->iic_base, piic->iic_irq);
return 0;
}
static void iic_ite_exit(void)
{
i2c_iic_del_bus(&iic_ite_ops);
iic_ite_release();
}
/* If modules is NOT defined when this file is compiled, then the MODULE_*
* macros will resolve to nothing
*/
MODULE_AUTHOR("MontaVista Software <www.mvista.com>");
MODULE_DESCRIPTION("I2C-Bus adapter routines for ITE IIC bus adapter");
MODULE_LICENSE("GPL");
module_param(base, int, 0);
module_param(irq, int, 0);
module_param(clock, int, 0);
module_param(own, int, 0);
/* Called when module is loaded or when kernel is initialized.
* If MODULES is defined when this file is compiled, then this function will
* resolve to init_module (the function called when insmod is invoked for a
* module). Otherwise, this function is called early in the boot, when the
* kernel is intialized. Check out /include/init.h to see how this works.
*/
module_init(iic_ite_init);
/* Resolves to module_cleanup when MODULES is defined. */
module_exit(iic_ite_exit);
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