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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)
126 lines
3.6 KiB
C
126 lines
3.6 KiB
C
/* dma.h: FRV DMA controller management
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*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#ifndef _ASM_DMA_H
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#define _ASM_DMA_H
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//#define DMA_DEBUG 1
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#include <linux/interrupt.h>
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#undef MAX_DMA_CHANNELS /* don't use kernel/dma.c */
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/* under 2.4 this is actually needed by the new bootmem allocator */
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#define MAX_DMA_ADDRESS PAGE_OFFSET
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/*
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* FRV DMA controller management
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*/
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typedef irqreturn_t (*dma_irq_handler_t)(int dmachan, unsigned long cstr, void *data);
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extern void frv_dma_init(void);
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extern int frv_dma_open(const char *devname,
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unsigned long dmamask,
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int dmacap,
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dma_irq_handler_t handler,
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unsigned long irq_flags,
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void *data);
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/* channels required */
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#define FRV_DMA_MASK_ANY ULONG_MAX /* any channel */
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/* capabilities required */
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#define FRV_DMA_CAP_DREQ 0x01 /* DMA request pin */
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#define FRV_DMA_CAP_DACK 0x02 /* DMA ACK pin */
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#define FRV_DMA_CAP_DONE 0x04 /* DMA done pin */
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extern void frv_dma_close(int dma);
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extern void frv_dma_config(int dma, unsigned long ccfr, unsigned long cctr, unsigned long apr);
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extern void frv_dma_start(int dma,
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unsigned long sba, unsigned long dba,
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unsigned long pix, unsigned long six, unsigned long bcl);
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extern void frv_dma_restart_circular(int dma, unsigned long six);
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extern void frv_dma_stop(int dma);
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extern int is_frv_dma_interrupting(int dma);
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extern void frv_dma_dump(int dma);
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extern void frv_dma_status_clear(int dma);
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#define FRV_DMA_NCHANS 8
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#define FRV_DMA_4CHANS 4
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#define FRV_DMA_8CHANS 8
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#define DMAC_CCFRx 0x00 /* channel configuration reg */
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#define DMAC_CCFRx_CM_SHIFT 16
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#define DMAC_CCFRx_CM_DA 0x00000000
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#define DMAC_CCFRx_CM_SCA 0x00010000
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#define DMAC_CCFRx_CM_DCA 0x00020000
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#define DMAC_CCFRx_CM_2D 0x00030000
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#define DMAC_CCFRx_ATS_SHIFT 8
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#define DMAC_CCFRx_RS_INTERN 0x00000000
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#define DMAC_CCFRx_RS_EXTERN 0x00000001
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#define DMAC_CCFRx_RS_SHIFT 0
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#define DMAC_CSTRx 0x08 /* channel status reg */
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#define DMAC_CSTRx_FS 0x0000003f
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#define DMAC_CSTRx_NE 0x00000100
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#define DMAC_CSTRx_FED 0x00000200
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#define DMAC_CSTRx_WER 0x00000800
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#define DMAC_CSTRx_RER 0x00001000
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#define DMAC_CSTRx_CE 0x00002000
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#define DMAC_CSTRx_INT 0x00800000
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#define DMAC_CSTRx_BUSY 0x80000000
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#define DMAC_CCTRx 0x10 /* channel control reg */
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#define DMAC_CCTRx_DSIZ_1 0x00000000
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#define DMAC_CCTRx_DSIZ_2 0x00000001
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#define DMAC_CCTRx_DSIZ_4 0x00000002
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#define DMAC_CCTRx_DSIZ_32 0x00000005
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#define DMAC_CCTRx_DAU_HOLD 0x00000000
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#define DMAC_CCTRx_DAU_INC 0x00000010
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#define DMAC_CCTRx_DAU_DEC 0x00000020
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#define DMAC_CCTRx_SSIZ_1 0x00000000
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#define DMAC_CCTRx_SSIZ_2 0x00000100
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#define DMAC_CCTRx_SSIZ_4 0x00000200
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#define DMAC_CCTRx_SSIZ_32 0x00000500
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#define DMAC_CCTRx_SAU_HOLD 0x00000000
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#define DMAC_CCTRx_SAU_INC 0x00001000
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#define DMAC_CCTRx_SAU_DEC 0x00002000
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#define DMAC_CCTRx_FC 0x08000000
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#define DMAC_CCTRx_ICE 0x10000000
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#define DMAC_CCTRx_IE 0x40000000
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#define DMAC_CCTRx_ACT 0x80000000
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#define DMAC_SBAx 0x18 /* source base address reg */
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#define DMAC_DBAx 0x20 /* data base address reg */
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#define DMAC_PIXx 0x28 /* primary index reg */
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#define DMAC_SIXx 0x30 /* secondary index reg */
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#define DMAC_BCLx 0x38 /* byte count limit reg */
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#define DMAC_APRx 0x40 /* alternate pointer reg */
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/*
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* required for PCI + MODULES
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*/
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#ifdef CONFIG_PCI
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extern int isa_dma_bridge_buggy;
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#else
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#define isa_dma_bridge_buggy (0)
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#endif
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#endif /* _ASM_DMA_H */
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