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linux/include/linux/ioc3.h
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

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/*
* 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) 2005 Stanislaw Skowronek <skylark@linux-mips.org>
*/
#ifndef _LINUX_IOC3_H
#define _LINUX_IOC3_H
#include <asm/sn/ioc3.h>
#define IOC3_MAX_SUBMODULES 32
#define IOC3_CLASS_NONE 0
#define IOC3_CLASS_BASE_IP27 1
#define IOC3_CLASS_BASE_IP30 2
#define IOC3_CLASS_MENET_123 3
#define IOC3_CLASS_MENET_4 4
#define IOC3_CLASS_CADDUO 5
#define IOC3_CLASS_SERIAL 6
/* One of these per IOC3 */
struct ioc3_driver_data {
struct list_head list;
int id; /* IOC3 sequence number */
/* PCI mapping */
unsigned long pma; /* physical address */
struct ioc3 __iomem *vma; /* pointer to registers */
struct pci_dev *pdev; /* PCI device */
/* IRQ stuff */
int dual_irq; /* set if separate IRQs are used */
int irq_io, irq_eth; /* IRQ numbers */
/* GPIO magic */
spinlock_t gpio_lock;
unsigned int gpdr_shadow;
/* NIC identifiers */
char nic_part[32];
char nic_serial[16];
char nic_mac[6];
/* submodule set */
int class;
void *data[IOC3_MAX_SUBMODULES]; /* for submodule use */
int active[IOC3_MAX_SUBMODULES]; /* set if probe succeeds */
/* is_ir_lock must be held while
* modifying sio_ie values, so
* we can be sure that sio_ie is
* not changing when we read it
* along with sio_ir.
*/
spinlock_t ir_lock; /* SIO_IE[SC] mod lock */
};
/* One per submodule */
struct ioc3_submodule {
char *name; /* descriptive submodule name */
struct module *owner; /* owning kernel module */
int ethernet; /* set for ethernet drivers */
int (*probe) (struct ioc3_submodule *, struct ioc3_driver_data *);
int (*remove) (struct ioc3_submodule *, struct ioc3_driver_data *);
int id; /* assigned by IOC3, index for the "data" array */
/* IRQ stuff */
unsigned int irq_mask; /* IOC3 IRQ mask, leave clear for Ethernet */
int reset_mask; /* non-zero if you want the ioc3.c module to reset interrupts */
int (*intr) (struct ioc3_submodule *, struct ioc3_driver_data *, unsigned int);
/* private submodule data */
void *data; /* assigned by submodule */
};
/**********************************
* Functions needed by submodules *
**********************************/
#define IOC3_W_IES 0
#define IOC3_W_IEC 1
/* registers a submodule for all existing and future IOC3 chips */
extern int ioc3_register_submodule(struct ioc3_submodule *);
/* unregisters a submodule */
extern void ioc3_unregister_submodule(struct ioc3_submodule *);
/* enables IRQs indicated by irq_mask for a specified IOC3 chip */
extern void ioc3_enable(struct ioc3_submodule *, struct ioc3_driver_data *, unsigned int);
/* ackowledges specified IRQs */
extern void ioc3_ack(struct ioc3_submodule *, struct ioc3_driver_data *, unsigned int);
/* disables IRQs indicated by irq_mask for a specified IOC3 chip */
extern void ioc3_disable(struct ioc3_submodule *, struct ioc3_driver_data *, unsigned int);
/* atomically sets GPCR bits */
extern void ioc3_gpcr_set(struct ioc3_driver_data *, unsigned int);
/* general ireg writer */
extern void ioc3_write_ireg(struct ioc3_driver_data *idd, uint32_t value, int reg);
#endif
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