Subversion Repositories openrisc_2011-10-31

/*
 * vr5xxx.S -- CPU specific support routines
 *
 * Copyright (c) 1999 Cygnus Solutions
 *
 * 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.
 */

/* This file cloned from vr4300.S by dlindsay@cygnus.com
 * and recoded to suit Vr5432 and Vr5000.
 * Should be no worse for Vr43{00,05,10}.
 * Specifically, __cpu_flush() has been changed (a) to allow for the hardware
 * difference (in set associativity) between the Vr5432 and Vr5000,
 * and (b) to flush the optional secondary cache of the Vr5000.
 */

/* Processor Revision Identifier (PRID) Register: Implementation Numbers */
#define IMPL_VR5432     0x54

/* Cache Constants not determinable dynamically */
#define VR5000_2NDLINE 32       /* secondary cache line size */
#define VR5432_LINE 32          /* I,Dcache line sizes */
#define VR5432_SIZE (16*1024)   /* I,Dcache half-size */


#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 and Vr5432 *CANNOT* have any secondary cache.
        # On those, SC (bit 17 of CONFIG register) is hard-wired to 1,
        # except that email from Dennis_Han@el.nec.com says that old
        # versions of the Vr5432 incorrectly hard-wired this bit to 0.
        # The Vr5000 has an optional direct-mapped secondary cache,
        # and the SC bit correctly indicates this.

        # So, for the 4300 and 5432 we want to just
        # flush the primary Data and Instruction caches.
        # For the 5000 it is desired to flush the secondary cache too.
        # There is an operation difference worth noting.
        # The 4300 and 5000 primary caches use VA bit 14 to choose cache set,
        # whereas 5432 primary caches use VA bit 0.

        # This code interprets the relevant Config register bits as
        # much as possible, except for the 5432.
        # The code therefore has some portability.
        # However, the associativity issues mean you should not just assume
        # that this code works anywhere. Also, the secondary cache set
        # size is hardwired, since the 5000 series does not define codes
        # for variant sizes.

        # Note: this version of the code flushes D$ before I$.
        #   It is difficult to construct a case where that matters, 
        #   but it cant hurt.

        mfc0    a0, C0_PRID     # a0 = Processor Revision register
        nop                     # dlindsay: unclear why the nops, but
        nop                     # vr4300.S had such so I do too.
        srl     a2, a0, PR_IMP  # want bits 8..15
        andi    a2, a2, 0x255   # mask: now a2 = Implementation # field
        li      a1, IMPL_VR5432
        beq     a1, a2, 8f      # use Vr5432-specific flush algorithm
        nop
        
        # Non-Vr5432 version of the code.
        # (The distinctions being: CONFIG is truthful about secondary cache, 
        # and we act as if the primary Icache and Dcache are direct mapped.)

        mfc0    t0, C0_CONFIG   # t0 = CONFIG register
        nop
        nop
        li      a1, 1           # a1=1, a useful constant

        srl     a2, t0, CR_IC   # want IC field of CONFIG
        andi    a2, a2, 0x7     # mask: now a2= code for Icache size
        add     a2, a2, 12      # +12
        sllv    a2, a1, a2      # a2=primary instruction cache size in bytes

        srl     a3, t0, CR_DC   # DC field of CONFIG
        andi    a3, a3, 0x7     # mask: now a3= code for Dcache size
        add     a3, a3, 12      # +12
        sllv    a3, a1, a3      # a3=primary data cache size in bytes

        li      t2, (1 << CR_IB) # t2=mask over IB boolean
        and     t2, t2, t0      # test IB field of CONFIG register value
        beqz    t2, 1f          # 
        li      a1, 16          # 16 bytes (branch shadow: always loaded.)
        li      a1, 32          # non-zero, then 32bytes
1:

        li      t2, (1 << CR_DB) # t2=mask over DB boolean
        and     t2, t2, t0      # test BD field of CONFIG register value
        beqz    t2, 2f          # 
        li      a0, 16          # 16bytes (branch shadow: always loaded.)
        li      a0, 32          # non-zero, then 32bytes
2:
        lui     t1, ((K0BASE >> 16) & 0xFFFF)
        ori     t1, t1, (K0BASE & 0xFFFF)

        # At this point,
        # a0 = primary Dcache line size in bytes
        # a1 = primary Icache line size in bytes
        # a2 = primary Icache size in bytes
        # a3 = primary Dcache size in bytes
        # t0 = CONFIG value
        # t1 = a round unmapped cached base address (we are in kernel mode)
        # t2,t3 scratch

        addi    t3, t1, 0       # t3=t1=start address for any cache
        add     t2, t3, a3      # t2=end adress+1 of Dcache
        sub     t2, t2, a0      # t2=address of last line in Dcache
3:
        cache   INDEX_WRITEBACK_INVALIDATE_D,0(t3)
        bne     t3, t2, 3b      # 
        addu    t3, a0          # (delay slot) increment by Dcache line size


        # Now check CONFIG to see if there is a secondary cache
        lui     t2, (1 << (CR_SC-16)) # t2=mask over SC boolean
        and     t2, t2, t0      # test SC in CONFIG
        bnez    t2, 6f
        
        # There is a secondary cache. Find out its sizes.
        
        srl     t3, t0, CR_SS   # want SS field of CONFIG
        andi    t3, t3, 0x3     # mask: now t3= code for cache size.
        beqz    t3, 4f
        lui     a3, ((512*1024)>>16)    # a3= 512K, code was 0
        addu    t3, -1                  # decrement code
        beqz    t3, 4f
        lui     a3, ((1024*1024)>>16)   # a3= 1 M, code  1
        addu    t3, -1                  # decrement code
        beqz    t3, 4f
        lui     a3, ((2*1024*1024)>>16) # a3= 2 M, code 2
        j       6f                      # no secondary cache, code 3

4:      # a3 = secondary cache size in bytes
        li      a0, VR5000_2NDLINE      # no codes assigned for other than 32

        # At this point,
        # a0 = secondary cache line size in bytes
        # a1 = primary Icache line size in bytes
        # a2 = primary Icache size in bytes
        # a3 = secondary cache size in bytes
        # t1 = a round unmapped cached base address (we are in kernel mode)
        # t2,t3 scratch
        
        addi    t3, t1, 0       # t3=t1=start address for any cache
        add     t2, t3, a3      # t2=end address+1 of secondary cache
        sub     t2, t2, a0      # t2=address of last line in secondary cache
5:
        cache   INDEX_WRITEBACK_INVALIDATE_SD,0(t3)
        bne     t3, t2, 5b
        addu    t3, a0          # (delay slot) increment by line size

        
6:      # Any optional secondary cache done.  Now do I-cache and return.

        # At this point,
        # a1 = primary Icache line size in bytes
        # a2 = primary Icache size in bytes
        # t1 = a round unmapped cached base address (we are in kernel mode)
        # t2,t3 scratch

        add     t2, t1, a2      # t2=end adress+1 of Icache
        sub     t2, t2, a1      # t2=address of last line in Icache
7:
        cache   INDEX_INVALIDATE_I,0(t1)
        bne     t1, t2, 7b
        addu    t1, a1          # (delay slot) increment by Icache line size

        j       ra      # return to the caller
        nop

8:

# Vr5432 version of the cpu_flush code.
# (The distinctions being: CONFIG can not be trusted about secondary
# cache (which does not exist). The primary caches use Virtual Address Bit 0
# to control set selection.

# Code does not consult CONFIG about cache sizes: knows the hardwired sizes.
# Since both I and D have the same size and line size, uses a merged loop.

        li      a0, VR5432_LINE
        li      a1, VR5432_SIZE
        lui     t1, ((K0BASE >> 16) & 0xFFFF)
        ori     t1, t1, (K0BASE & 0xFFFF)

        # a0 = cache line size in bytes
        # a1 = 1/2 cache size in bytes
        # t1 = a round unmapped cached base address (we are in kernel mode)

        add     t2, t1, a1      # t2=end address+1
        sub     t2, t2, a0      # t2=address of last line in Icache

9:
        cache   INDEX_WRITEBACK_INVALIDATE_D,0(t1)      # set 0
        cache   INDEX_WRITEBACK_INVALIDATE_D,1(t1)      # set 1
        cache   INDEX_INVALIDATE_I,0(t1)        # set 0
        cache   INDEX_INVALIDATE_I,1(t1)        # set 1
        bne     t1, t2, 9b
        addu    t1, 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 vr5xxx.S */