Retro68/gcc/libgloss/mips/vr4300.S
2012-03-27 01:51:53 +02:00

342 lines
8.0 KiB
ArmAsm

/*
* vr4300.S -- CPU specific support routines
*
* Copyright (c) 1995,1996 Cygnus Support
*
* The authors hereby grant permission to use, copy, modify, distribute,
* and license this software and its documentation for any purpose, provided
* that existing copyright notices are retained in all copies and that this
* notice is included verbatim in any distributions. No written agreement,
* license, or royalty fee is required for any of the authorized uses.
* Modifications to this software may be copyrighted by their authors
* and need not follow the licensing terms described here, provided that
* the new terms are clearly indicated on the first page of each file where
* they apply.
*/
#ifndef __mips64
.set mips3
#endif
#ifdef __mips16
/* This file contains 32 bit assembly code. */
.set nomips16
#endif
#include "regs.S"
.text
.align 2
# Taken from "R4300 Preliminary RISC Processor Specification
# Revision 2.0 January 1995" page 39: "The Count
# register... increments at a constant rate... at one-half the
# PClock speed."
# We can use this fact to provide small polled delays.
.globl __cpu_timer_poll
.ent __cpu_timer_poll
__cpu_timer_poll:
.set noreorder
# in: a0 = (unsigned int) number of PClock ticks to wait for
# out: void
# The Vr4300 counter updates at half PClock, so divide by 2 to
# get counter delta:
bnezl a0, 1f # continue if delta non-zero
srl a0, a0, 1 # divide ticks by 2 {DELAY SLOT}
# perform a quick return to the caller:
j ra
nop # {DELAY SLOT}
1:
mfc0 v0, C0_COUNT # get current counter value
nop
nop
# We cannot just do the simple test, of adding our delta onto
# the current value (ignoring overflow) and then checking for
# equality. The counter is incrementing every two PClocks,
# which means the counter value can change between
# instructions, making it hard to sample at the exact value
# desired.
# However, we do know that our entry delta value is less than
# half the number space (since we divide by 2 on entry). This
# means we can use a difference in signs to indicate timer
# overflow.
addu a0, v0, a0 # unsigned add (ignore overflow)
# We know have our end value (which will have been
# sign-extended to fill the 64bit register value).
2:
# get current counter value:
mfc0 v0, C0_COUNT
nop
nop
# This is an unsigned 32bit subtraction:
subu v0, a0, v0 # delta = (end - now) {DELAY SLOT}
bgtzl v0, 2b # looping back is most likely
nop
# We have now been delayed (in the foreground) for AT LEAST
# the required number of counter ticks.
j ra # return to caller
nop # {DELAY SLOT}
.set reorder
.end __cpu_timer_poll
# Flush the processor caches to memory:
.globl __cpu_flush
.ent __cpu_flush
__cpu_flush:
.set noreorder
# NOTE: The Vr4300 *CANNOT* have any secondary cache (bit 17
# of the CONFIG registered is hard-wired to 1). We just
# provide code to flush the Data and Instruction caches.
# Even though the Vr4300 has hard-wired cache and cache line
# sizes, we still interpret the relevant Config register
# bits. This allows this code to be used for other conforming
# MIPS architectures if desired.
# Get the config register
mfc0 a0, C0_CONFIG
nop
nop
li a1, 1 # a useful constant
#
srl a2, a0, 9 # bits 11..9 for instruction cache size
andi a2, a2, 0x7 # 3bits of information
add a2, a2, 12 # get full power-of-2 value
sllv a2, a1, a2 # instruction cache size
#
srl a3, a0, 6 # bits 8..6 for data cache size
andi a3, a3, 0x7 # 3bits of information
add a3, a3, 12 # get full power-of-2 value
sllv a3, a1, a3 # data cache size
#
li a1, (1 << 5) # check IB (instruction cache line size)
and a1, a0, a1 # mask against the CONFIG register value
beqz a1, 1f # branch on result of delay slot operation
nop
li a1, 32 # non-zero, then 32bytes
j 2f # continue
nop
1:
li a1, 16 # 16bytes
2:
#
li t0, (1 << 4) # check DB (data cache line size)
and a0, a0, t0 # mask against the CONFIG register value
beqz a0, 3f # branch on result of delay slot operation
nop
li a0, 32 # non-zero, then 32bytes
j 4f # continue
nop
3:
li a0, 16 # 16bytes
4:
#
# a0 = data cache line size
# a1 = instruction cache line size
# a2 = instruction cache size
# a3 = data cache size
#
lui t0, ((K0BASE >> 16) & 0xFFFF)
ori t0, t0, (K0BASE & 0xFFFF)
addu t1, t0, a2 # end cache address
subu t2, a1, 1 # line size mask
not t2 # invert the mask
and t3, t0, t2 # get start address
addu t1, -1
and t1, t2 # get end address
5:
cache INDEX_INVALIDATE_I,0(t3)
bne t3, t1, 5b
addu t3, a1
#
addu t1, t0, a3 # end cache address
subu t2, a0, 1 # line size mask
not t2 # invert the mask
and t3, t0, t2 # get start address
addu t1, -1
and t1, t2 # get end address
6:
cache INDEX_WRITEBACK_INVALIDATE_D,0(t3)
bne t3, t1, 6b
addu t3, a0
#
j ra # return to the caller
nop
.set reorder
.end __cpu_flush
# NOTE: This variable should *NOT* be addressed relative to
# the $gp register since this code is executed before $gp is
# initialised... hence we leave it in the text area. This will
# cause problems if this routine is ever ROMmed:
.globl __buserr_cnt
__buserr_cnt:
.word 0
.align 3
__k1_save:
.word 0
.word 0
.align 2
.ent __buserr
.globl __buserr
__buserr:
.set noat
.set noreorder
# k0 and k1 available for use:
mfc0 k0,C0_CAUSE
nop
nop
andi k0,k0,0x7c
sub k0,k0,7 << 2
beq k0,$0,__buserr_do
nop
# call the previous handler
la k0,__previous
jr k0
nop
#
__buserr_do:
# TODO: check that the cause is indeed a bus error
# - if not then just jump to the previous handler
la k0,__k1_save
sd k1,0(k0)
#
la k1,__buserr_cnt
lw k0,0(k1) # increment counter
addu k0,1
sw k0,0(k1)
#
la k0,__k1_save
ld k1,0(k0)
#
mfc0 k0,C0_EPC
nop
nop
addu k0,k0,4 # skip offending instruction
mtc0 k0,C0_EPC # update EPC
nop
nop
eret
# j k0
# rfe
.set reorder
.set at
.end __buserr
__exception_code:
.set noreorder
lui k0,%hi(__buserr)
daddiu k0,k0,%lo(__buserr)
jr k0
nop
.set reorder
__exception_code_end:
.data
__previous:
.space (__exception_code_end - __exception_code)
# This subtracting two addresses is working
# but is not garenteed to continue working.
# The assemble reserves the right to put these
# two labels into different frags, and then
# cant take their difference.
.text
.ent __default_buserr_handler
.globl __default_buserr_handler
__default_buserr_handler:
.set noreorder
# attach our simple bus error handler:
# in: void
# out: void
mfc0 a0,C0_SR
nop
li a1,SR_BEV
and a1,a1,a0
beq a1,$0,baseaddr
lui a0,0x8000 # delay slot
lui a0,0xbfc0
daddiu a0,a0,0x0200
baseaddr:
daddiu a0,a0,0x0180
# a0 = base vector table address
la a1,__exception_code_end
la a2,__exception_code
subu a1,a1,a2
la a3,__previous
# there must be a better way of doing this????
copyloop:
lw v0,0(a0)
sw v0,0(a3)
lw v0,0(a2)
sw v0,0(a0)
daddiu a0,a0,4
daddiu a2,a2,4
daddiu a3,a3,4
subu a1,a1,4
bne a1,$0,copyloop
nop
la a0,__buserr_cnt
sw $0,0(a0)
j ra
nop
.set reorder
.end __default_buserr_handler
.ent __restore_buserr_handler
.globl __restore_buserr_handler
__restore_buserr_handler:
.set noreorder
# restore original (monitor) bus error handler
# in: void
# out: void
mfc0 a0,C0_SR
nop
li a1,SR_BEV
and a1,a1,a0
beq a1,$0,res_baseaddr
lui a0,0x8000 # delay slot
lui a0,0xbfc0
daddiu a0,a0,0x0200
res_baseaddr:
daddiu a0,a0,0x0180
# a0 = base vector table address
la a1,__exception_code_end
la a3,__exception_code
subu a1,a1,a3
la a3,__previous
# there must be a better way of doing this????
res_copyloop:
lw v0,0(a3)
sw v0,0(a0)
daddiu a0,a0,4
daddiu a3,a3,4
subu a1,a1,4
bne a1,$0,res_copyloop
nop
j ra
nop
.set reorder
.end __restore_buserr_handler
.ent __buserr_count
.globl __buserr_count
__buserr_count:
.set noreorder
# restore original (monitor) bus error handler
# in: void
# out: unsigned int __buserr_cnt
la v0,__buserr_cnt
lw v0,0(v0)
j ra
nop
.set reorder
.end __buserr_count
/* EOF vr4300.S */