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linux/arch/frv/kernel/head.S
David Howells 28baebae73 [PATCH] FRV: Use virtual interrupt disablement 
Make the FRV arch use virtual interrupt disablement because accesses to the
processor status register (PSR) are relatively slow and because we will
soon have the need to deal with multiple interrupt controls at the same
time (separate h/w and inter-core interrupts).

The way this is done is to dedicate one of the four integer condition code
registers (ICC2) to maintaining a virtual interrupt disablement state
whilst inside the kernel.  This uses the ICC2.Z flag (Zero) to indicate
whether the interrupts are virtually disabled and the ICC2.C flag (Carry)
to indicate whether the interrupts are physically disabled.

ICC2.Z is set to indicate interrupts are virtually disabled.  ICC2.C is set
to indicate interrupts are physically enabled.  Under normal running
conditions Z==0 and C==1.

Disabling interrupts with local_irq_disable() doesn't then actually
physically disable interrupts - it merely sets ICC2.Z to 1.  Should an
interrupt then happen, the exception prologue will note ICC2.Z is set and
branch out of line using one instruction (an unlikely BEQ).  Here it will
physically disable interrupts and clear ICC2.C.

When it comes time to enable interrupts (local_irq_enable()), this simply
clears the ICC2.Z flag and invokes a trap #2 if both Z and C flags are
clear (the HI integer condition).  This can be done with the TIHI
conditional trap instruction.

The trap then physically reenables interrupts and sets ICC2.C again.  Upon
returning the interrupt will be taken as interrupts will then be enabled.
Note that whilst processing the trap, the whole exceptions system is
disabled, and so an interrupt can't happen till it returns.

If no pending interrupt had happened, ICC2.C would still be set, the HI
condition would not be fulfilled, and no trap will happen.

Saving interrupts (local_irq_save) is simply a matter of pulling the ICC2.Z
flag out of the CCR register, shifting it down and masking it off.  This
gives a result of 0 if interrupts were enabled and 1 if they weren't.

Restoring interrupts (local_irq_restore) is then a matter of taking the
saved value mentioned previously and XOR'ing it against 1.  If it was one,
the result will be zero, and if it was zero the result will be non-zero.
This result is then used to affect the ICC2.Z flag directly (it is a
condition code flag after all).  An XOR instruction does not affect the
Carry flag, and so that bit of state is unchanged.  The two flags can then
be sampled to see if they're both zero using the trap (TIHI) as for the
unconditional reenablement (local_irq_enable).

This patch also:

 (1) Modifies the debugging stub (break.S) to handle single-stepping crossing
     into the trap #2 handler and into virtually disabled interrupts.

 (2) Removes superseded fixup pointers from the second instructions in the trap
     tables (there's no a separate fixup table for this).

 (3) Declares the trap #3 vector for use in .org directives in the trap table.

 (4) Moves irq_enter() and irq_exit() in do_IRQ() to avoid problems with
     virtual interrupt handling, and removes the duplicate code that has now
     been folded into irq_exit() (softirq and preemption handling).

 (5) Tells the compiler in the arch Makefile that ICC2 is now reserved.

 (6) Documents the in-kernel ABI, including the virtual interrupts.

 (7) Renames the old irq management functions to different names.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-14 16:09:35 -08:00

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/* head.S: kernel entry point for FR-V kernel
*
* Copyright (C) 2003, 2004 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* 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.
*/
#include <linux/config.h>
#include <linux/threads.h>
#include <linux/linkage.h>
#include <asm/ptrace.h>
#include <asm/page.h>
#include <asm/spr-regs.h>
#include <asm/mb86943a.h>
#include <asm/cache.h>
#include "head.inc"
###############################################################################
#
# void _boot(unsigned long magic, char *command_line) __attribute__((noreturn))
#
# - if magic is 0xdead1eaf, then command_line is assumed to point to the kernel
# command line string
#
###############################################################################
.section .text.head,"ax"
.balign 4
.globl _boot, __head_reference
.type _boot,@function
_boot:
__head_reference:
sethi.p %hi(LED_ADDR),gr30
setlo %lo(LED_ADDR),gr30
LEDS 0x0000
# calculate reference address for PC-relative stuff
call 0f
0: movsg lr,gr26
addi gr26,#__head_reference-0b,gr26
# invalidate and disable both of the caches and turn off the memory access checking
dcef @(gr0,gr0),1
bar
sethi.p %hi(~(HSR0_ICE|HSR0_DCE|HSR0_CBM|HSR0_EIMMU|HSR0_EDMMU)),gr4
setlo %lo(~(HSR0_ICE|HSR0_DCE|HSR0_CBM|HSR0_EIMMU|HSR0_EDMMU)),gr4
movsg hsr0,gr5
and gr4,gr5,gr5
movgs gr5,hsr0
movsg hsr0,gr5
LEDS 0x0001
icei @(gr0,gr0),1
dcei @(gr0,gr0),1
bar
# turn the instruction cache back on
sethi.p %hi(HSR0_ICE),gr4
setlo %lo(HSR0_ICE),gr4
movsg hsr0,gr5
or gr4,gr5,gr5
movgs gr5,hsr0
movsg hsr0,gr5
bar
LEDS 0x0002
# retrieve the parameters (including command line) before we overwrite them
sethi.p %hi(0xdead1eaf),gr7
setlo %lo(0xdead1eaf),gr7
subcc gr7,gr8,gr0,icc0
bne icc0,#0,__head_no_parameters
sethi.p %hi(redboot_command_line-1),gr6
setlo %lo(redboot_command_line-1),gr6
sethi.p %hi(__head_reference),gr4
setlo %lo(__head_reference),gr4
sub gr6,gr4,gr6
add.p gr6,gr26,gr6
subi gr9,#1,gr9
setlos.p #511,gr4
setlos #1,gr5
__head_copy_cmdline:
ldubu.p @(gr9,gr5),gr16
subicc gr4,#1,gr4,icc0
stbu.p gr16,@(gr6,gr5)
subicc gr16,#0,gr0,icc1
bls icc0,#0,__head_end_cmdline
bne icc1,#1,__head_copy_cmdline
__head_end_cmdline:
stbu gr0,@(gr6,gr5)
__head_no_parameters:
###############################################################################
#
# we need to relocate the SDRAM to 0x00000000 (linux) or 0xC0000000 (uClinux)
# - note that we're going to have to run entirely out of the icache whilst
# fiddling with the SDRAM controller registers
#
###############################################################################
#ifdef CONFIG_MMU
call __head_fr451_describe_sdram
#else
movsg psr,gr5
srli gr5,#28,gr5
subicc gr5,#3,gr0,icc0
beq icc0,#0,__head_fr551_sdram
call __head_fr401_describe_sdram
bra __head_do_sdram
__head_fr551_sdram:
call __head_fr555_describe_sdram
LEDS 0x000d
__head_do_sdram:
#endif
# preload the registers with invalid values in case any DBR/DARS are marked not present
sethi.p %hi(0xfe000000),gr17 ; unused SDRAM DBR value
setlo %lo(0xfe000000),gr17
or.p gr17,gr0,gr20
or gr17,gr0,gr21
or.p gr17,gr0,gr22
or gr17,gr0,gr23
# consult the SDRAM controller CS address registers
cld @(gr14,gr0 ),gr20, cc0,#1 ; DBR0 / DARS0
cld @(gr14,gr11),gr21, cc1,#1 ; DBR1 / DARS1
cld @(gr14,gr12),gr22, cc2,#1 ; DBR2 / DARS2
cld.p @(gr14,gr13),gr23, cc3,#1 ; DBR3 / DARS3
sll gr20,gr15,gr20 ; shift values up for FR551
sll gr21,gr15,gr21
sll gr22,gr15,gr22
sll gr23,gr15,gr23
LEDS 0x0003
# assume the lowest valid CS line to be the SDRAM base and get its address
subcc gr20,gr17,gr0,icc0
subcc.p gr21,gr17,gr0,icc1
subcc gr22,gr17,gr0,icc2
subcc.p gr23,gr17,gr0,icc3
ckne icc0,cc4 ; T if DBR0 != 0xfe000000
ckne icc1,cc5
ckne icc2,cc6
ckne icc3,cc7
cor gr23,gr0,gr24, cc7,#1 ; GR24 = SDRAM base
cor gr22,gr0,gr24, cc6,#1
cor gr21,gr0,gr24, cc5,#1
cor gr20,gr0,gr24, cc4,#1
# calculate the displacement required to get the SDRAM into the right place in memory
sethi.p %hi(__sdram_base),gr16
setlo %lo(__sdram_base),gr16
sub gr16,gr24,gr16 ; delta = __sdram_base - DBRx
# calculate the new values to go in the controller regs
cadd.p gr20,gr16,gr20, cc4,#1 ; DCS#0 (new) = DCS#0 (old) + delta
cadd gr21,gr16,gr21, cc5,#1
cadd.p gr22,gr16,gr22, cc6,#1
cadd gr23,gr16,gr23, cc7,#1
srl gr20,gr15,gr20 ; shift values down for FR551
srl gr21,gr15,gr21
srl gr22,gr15,gr22
srl gr23,gr15,gr23
# work out the address at which the reg updater resides and lock it into icache
# also work out the address the updater will jump to when finished
sethi.p %hi(__head_move_sdram-__head_reference),gr18
setlo %lo(__head_move_sdram-__head_reference),gr18
sethi.p %hi(__head_sdram_moved-__head_reference),gr19
setlo %lo(__head_sdram_moved-__head_reference),gr19
add.p gr18,gr26,gr18
add gr19,gr26,gr19
add.p gr19,gr16,gr19 ; moved = addr + (__sdram_base - DBRx)
add gr18,gr5,gr4 ; two cachelines probably required
icpl gr18,gr0,#1 ; load and lock the cachelines
icpl gr4,gr0,#1
LEDS 0x0004
membar
bar
jmpl @(gr18,gr0)
.balign L1_CACHE_BYTES
__head_move_sdram:
cst gr20,@(gr14,gr0 ), cc4,#1
cst gr21,@(gr14,gr11), cc5,#1
cst gr22,@(gr14,gr12), cc6,#1
cst gr23,@(gr14,gr13), cc7,#1
cld @(gr14,gr0 ),gr20, cc4,#1
cld @(gr14,gr11),gr21, cc5,#1
cld @(gr14,gr12),gr22, cc4,#1
cld @(gr14,gr13),gr23, cc7,#1
bar
membar
jmpl @(gr19,gr0)
.balign L1_CACHE_BYTES
__head_sdram_moved:
icul gr18
add gr18,gr5,gr4
icul gr4
icei @(gr0,gr0),1
dcei @(gr0,gr0),1
LEDS 0x0005
# recalculate reference address
call 0f
0: movsg lr,gr26
addi gr26,#__head_reference-0b,gr26
###############################################################################
#
# move the kernel image down to the bottom of the SDRAM
#
###############################################################################
sethi.p %hi(__kernel_image_size_no_bss+15),gr4
setlo %lo(__kernel_image_size_no_bss+15),gr4
srli.p gr4,#4,gr4 ; count
or gr26,gr26,gr16 ; source
sethi.p %hi(__sdram_base),gr17 ; destination
setlo %lo(__sdram_base),gr17
setlos #8,gr5
sub.p gr16,gr5,gr16 ; adjust src for LDDU
sub gr17,gr5,gr17 ; adjust dst for LDDU
sethi.p %hi(__head_move_kernel-__head_reference),gr18
setlo %lo(__head_move_kernel-__head_reference),gr18
sethi.p %hi(__head_kernel_moved-__head_reference+__sdram_base),gr19
setlo %lo(__head_kernel_moved-__head_reference+__sdram_base),gr19
add gr18,gr26,gr18
icpl gr18,gr0,#1
jmpl @(gr18,gr0)
.balign 32
__head_move_kernel:
lddu @(gr16,gr5),gr10
lddu @(gr16,gr5),gr12
stdu.p gr10,@(gr17,gr5)
subicc gr4,#1,gr4,icc0
stdu.p gr12,@(gr17,gr5)
bhi icc0,#0,__head_move_kernel
jmpl @(gr19,gr0)
.balign 32
__head_kernel_moved:
icul gr18
icei @(gr0,gr0),1
dcei @(gr0,gr0),1
LEDS 0x0006
# recalculate reference address
call 0f
0: movsg lr,gr26
addi gr26,#__head_reference-0b,gr26
###############################################################################
#
# rearrange the iomem map and set the protection registers
#
###############################################################################
#ifdef CONFIG_MMU
LEDS 0x3301
call __head_fr451_set_busctl
LEDS 0x3303
call __head_fr451_survey_sdram
LEDS 0x3305
call __head_fr451_set_protection
#else
movsg psr,gr5
srli gr5,#PSR_IMPLE_SHIFT,gr5
subicc gr5,#PSR_IMPLE_FR551,gr0,icc0
beq icc0,#0,__head_fr555_memmap
subicc gr5,#PSR_IMPLE_FR451,gr0,icc0
beq icc0,#0,__head_fr451_memmap
LEDS 0x3101
call __head_fr401_set_busctl
LEDS 0x3103
call __head_fr401_survey_sdram
LEDS 0x3105
call __head_fr401_set_protection
bra __head_done_memmap
__head_fr451_memmap:
LEDS 0x3301
call __head_fr401_set_busctl
LEDS 0x3303
call __head_fr401_survey_sdram
LEDS 0x3305
call __head_fr451_set_protection
bra __head_done_memmap
__head_fr555_memmap:
LEDS 0x3501
call __head_fr555_set_busctl
LEDS 0x3503
call __head_fr555_survey_sdram
LEDS 0x3505
call __head_fr555_set_protection
__head_done_memmap:
#endif
LEDS 0x0007
###############################################################################
#
# turn the data cache and MMU on
# - for the FR451 this'll mean that the window through which the kernel is
# viewed will change
#
###############################################################################
#ifdef CONFIG_MMU
#define MMUMODE HSR0_EIMMU|HSR0_EDMMU|HSR0_EXMMU|HSR0_EDAT|HSR0_XEDAT
#else
#define MMUMODE HSR0_EIMMU|HSR0_EDMMU
#endif
movsg hsr0,gr5
sethi.p %hi(MMUMODE),gr4
setlo %lo(MMUMODE),gr4
or gr4,gr5,gr5
#if defined(CONFIG_FRV_DEFL_CACHE_WTHRU)
sethi.p %hi(HSR0_DCE|HSR0_CBM_WRITE_THRU),gr4
setlo %lo(HSR0_DCE|HSR0_CBM_WRITE_THRU),gr4
#elif defined(CONFIG_FRV_DEFL_CACHE_WBACK)
sethi.p %hi(HSR0_DCE|HSR0_CBM_COPY_BACK),gr4
setlo %lo(HSR0_DCE|HSR0_CBM_COPY_BACK),gr4
#elif defined(CONFIG_FRV_DEFL_CACHE_WBEHIND)
sethi.p %hi(HSR0_DCE|HSR0_CBM_COPY_BACK),gr4
setlo %lo(HSR0_DCE|HSR0_CBM_COPY_BACK),gr4
movsg psr,gr6
srli gr6,#24,gr6
cmpi gr6,#0x50,icc0 // FR451
beq icc0,#0,0f
cmpi gr6,#0x40,icc0 // FR405
bne icc0,#0,1f
0:
# turn off write-allocate
sethi.p %hi(HSR0_NWA),gr6
setlo %lo(HSR0_NWA),gr6
or gr4,gr6,gr4
1:
#else
#error No default cache configuration set
#endif
or gr4,gr5,gr5
movgs gr5,hsr0
bar
LEDS 0x0008
sethi.p %hi(__head_mmu_enabled),gr19
setlo %lo(__head_mmu_enabled),gr19
jmpl @(gr19,gr0)
__head_mmu_enabled:
icei @(gr0,gr0),#1
dcei @(gr0,gr0),#1
LEDS 0x0009
#ifdef CONFIG_MMU
call __head_fr451_finalise_protection
#endif
LEDS 0x000a
###############################################################################
#
# set up the runtime environment
#
###############################################################################
# clear the BSS area
sethi.p %hi(__bss_start),gr4
setlo %lo(__bss_start),gr4
sethi.p %hi(_end),gr5
setlo %lo(_end),gr5
or.p gr0,gr0,gr18
or gr0,gr0,gr19
0:
stdi gr18,@(gr4,#0)
stdi gr18,@(gr4,#8)
stdi gr18,@(gr4,#16)
stdi.p gr18,@(gr4,#24)
addi gr4,#24,gr4
subcc gr5,gr4,gr0,icc0
bhi icc0,#2,0b
LEDS 0x000b
# save the SDRAM details
sethi.p %hi(__sdram_old_base),gr4
setlo %lo(__sdram_old_base),gr4
st gr24,@(gr4,gr0)
sethi.p %hi(__sdram_base),gr5
setlo %lo(__sdram_base),gr5
sethi.p %hi(memory_start),gr4
setlo %lo(memory_start),gr4
st gr5,@(gr4,gr0)
add gr25,gr5,gr25
sethi.p %hi(memory_end),gr4
setlo %lo(memory_end),gr4
st gr25,@(gr4,gr0)
# point the TBR at the kernel trap table
sethi.p %hi(__entry_kerneltrap_table),gr4
setlo %lo(__entry_kerneltrap_table),gr4
movgs gr4,tbr
# set up the exception frame for init
sethi.p %hi(__kernel_frame0_ptr),gr28
setlo %lo(__kernel_frame0_ptr),gr28
sethi.p %hi(_gp),gr16
setlo %lo(_gp),gr16
sethi.p %hi(__entry_usertrap_table),gr4
setlo %lo(__entry_usertrap_table),gr4
lddi @(gr28,#0),gr28 ; load __frame & current
ldi.p @(gr29,#4),gr15 ; set current_thread
or gr0,gr0,fp
or gr28,gr0,sp
sti.p gr4,@(gr28,REG_TBR)
setlos #ISR_EDE|ISR_DTT_DIVBYZERO|ISR_EMAM_EXCEPTION,gr5
movgs gr5,isr
# turn on and off various CPU services
movsg psr,gr22
sethi.p %hi(#PSR_EM|PSR_EF|PSR_CM|PSR_NEM),gr4
setlo %lo(#PSR_EM|PSR_EF|PSR_CM|PSR_NEM),gr4
or gr22,gr4,gr22
movgs gr22,psr
andi gr22,#~(PSR_PIL|PSR_PS|PSR_S),gr22
ori gr22,#PSR_ET,gr22
sti gr22,@(gr28,REG_PSR)
###############################################################################
#
# set up the registers and jump into the kernel
#
###############################################################################
LEDS 0x000c
# initialise the processor and the peripherals
#call SYMBOL_NAME(processor_init)
#call SYMBOL_NAME(unit_init)
#LEDS 0x0aff
sethi.p #0xe5e5,gr3
setlo #0xe5e5,gr3
or.p gr3,gr0,gr4
or gr3,gr0,gr5
or.p gr3,gr0,gr6
or gr3,gr0,gr7
or.p gr3,gr0,gr8
or gr3,gr0,gr9
or.p gr3,gr0,gr10
or gr3,gr0,gr11
or.p gr3,gr0,gr12
or gr3,gr0,gr13
or.p gr3,gr0,gr14
or gr3,gr0,gr17
or.p gr3,gr0,gr18
or gr3,gr0,gr19
or.p gr3,gr0,gr20
or gr3,gr0,gr21
or.p gr3,gr0,gr23
or gr3,gr0,gr24
or.p gr3,gr0,gr25
or gr3,gr0,gr26
or.p gr3,gr0,gr27
# or gr3,gr0,gr30
or gr3,gr0,gr31
movgs gr0,lr
movgs gr0,lcr
movgs gr0,ccr
movgs gr0,cccr
# initialise the virtual interrupt handling
subcc gr0,gr0,gr0,icc2 /* set Z, clear C */
#ifdef CONFIG_MMU
movgs gr3,scr2
movgs gr3,scr3
#endif
LEDS 0x0fff
# invoke the debugging stub if present
# - arch/frv/kernel/debug-stub.c will shift control directly to init/main.c
# (it will not return here)
break
.globl __debug_stub_init_break
__debug_stub_init_break:
# however, if you need to use an ICE, and don't care about using any userspace
# debugging tools (such as the ptrace syscall), you can just step over the break
# above and get to the kernel this way
# look at arch/frv/kernel/debug-stub.c: debug_stub_init() to see what you've missed
call start_kernel
.globl __head_end
__head_end:
.size _boot, .-_boot
# provide a point for GDB to place a break
.section .text.start,"ax"
.globl _start
.balign 4
_start:
call _boot
.previous
###############################################################################
#
# split a tile off of the region defined by GR8-GR9
#
# ENTRY: EXIT:
# GR4 - IAMPR value representing tile
# GR5 - DAMPR value representing tile
# GR6 - IAMLR value representing tile
# GR7 - DAMLR value representing tile
# GR8 region base pointer [saved]
# GR9 region top pointer updated to exclude new tile
# GR11 xAMLR mask [saved]
# GR25 SDRAM size [saved]
# GR30 LED address [saved]
#
# - GR8 and GR9 should be rounded up/down to the nearest megabyte before calling
#
###############################################################################
.globl __head_split_region
.type __head_split_region,@function
__head_split_region:
subcc.p gr9,gr8,gr4,icc0
setlos #31,gr5
scan.p gr4,gr0,gr6
beq icc0,#0,__head_region_empty
sub.p gr5,gr6,gr6 ; bit number of highest set bit (1MB=>20)
setlos #1,gr4
sll.p gr4,gr6,gr4 ; size of region (1 << bitno)
subi gr6,#17,gr6 ; 1MB => 0x03
slli.p gr6,#4,gr6 ; 1MB => 0x30
sub gr9,gr4,gr9 ; move uncovered top down
or gr9,gr6,gr4
ori gr4,#xAMPRx_S_USER|xAMPRx_C_CACHED|xAMPRx_V,gr4
or.p gr4,gr0,gr5
and gr4,gr11,gr6
and.p gr5,gr11,gr7
bralr
__head_region_empty:
or.p gr0,gr0,gr4
or gr0,gr0,gr5
or.p gr0,gr0,gr6
or gr0,gr0,gr7
bralr
.size __head_split_region, .-__head_split_region
###############################################################################
#
# write the 32-bit hex number in GR8 to ttyS0
#
###############################################################################
#if 0
.globl __head_write_to_ttyS0
.type __head_write_to_ttyS0,@function
__head_write_to_ttyS0:
sethi.p %hi(0xfeff9c00),gr31
setlo %lo(0xfeff9c00),gr31
setlos #8,gr20
0: ldubi @(gr31,#5*8),gr21
andi gr21,#0x60,gr21
subicc gr21,#0x60,gr21,icc0
bne icc0,#0,0b
1: srli gr8,#28,gr21
slli gr8,#4,gr8
addi gr21,#'0',gr21
subicc gr21,#'9',gr0,icc0
bls icc0,#2,2f
addi gr21,#'A'-'0'-10,gr21
2:
stbi gr21,@(gr31,#0*8)
subicc gr20,#1,gr20,icc0
bhi icc0,#2,1b
setlos #'\r',gr21
stbi gr21,@(gr31,#0*8)
setlos #'\n',gr21
stbi gr21,@(gr31,#0*8)
3: ldubi @(gr31,#5*8),gr21
andi gr21,#0x60,gr21
subicc gr21,#0x60,gr21,icc0
bne icc0,#0,3b
bralr
.size __head_write_to_ttyS0, .-__head_write_to_ttyS0
#endif
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