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@@ -1,3 +1,5 @@
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+; WARNING : The refill handler has been modified, see below !!!
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+
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/*
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* Copyright (C) 2003 Axis Communications AB
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*
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@@ -61,6 +63,14 @@
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; Note that the code is optimized to minimize stalls (makes the code harder
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; to read).
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;
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+; WARNING !!!
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+; Modified by Mikael Asker 060725: added a workaround for strange TLB
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+; behavior. If the same PTE is present in more than one set, the TLB
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+; doesn't recognize it and we get stuck in a loop of refill exceptions.
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+; The workaround detects such loops and exits them by flushing
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+; the TLB contents. The problem and workaround were verified
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+; in VCS by Mikael Starvik.
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+;
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; Each page is 8 KB. Each PMD holds 8192/4 PTEs (each PTE is 4 bytes) so each
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; PMD holds 16 MB of virtual memory.
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; Bits 0-12 : Offset within a page
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@@ -68,6 +78,11 @@
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; Bits 24-31 : PMD offset within the PGD
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.macro MMU_REFILL_HANDLER handler, mmu
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+ .data
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+1: .dword 0 ; refill_count
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+ ; == 0 <=> last_refill_cause is invalid
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+2: .dword 0 ; last_refill_cause
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+ .text
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.globl \handler
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\handler:
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subq 4, $sp
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@@ -76,42 +91,96 @@
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subq 4, $sp
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move \mmu, $srs ; Select MMU support register bank
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move.d $acr, [$sp]
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- subq 4, $sp
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- move.d $r0, [$sp]
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+ subq 12, $sp
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+ move.d 1b, $acr ; Point to refill_count
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+ movem $r2, [$sp]
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+
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+ test.d [$acr] ; refill_count == 0 ?
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+ beq 5f ; yes, last_refill_cause is invalid
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+ move.d $acr, $r1
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+
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+ ; last_refill_cause is valid, investigate cause
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+ addq 4, $r1 ; Point to last_refill_cause
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+ move $s3, $r0 ; Get rw_mm_cause
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+ move.d [$r1], $r2 ; Get last_refill_cause
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+ cmp.d $r0, $r2 ; rw_mm_cause == last_refill_cause ?
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+ beq 6f ; yes, increment count
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+ moveq 1, $r2
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+
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+ ; rw_mm_cause != last_refill_cause
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+ move.d $r2, [$acr] ; refill_count = 1
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+ move.d $r0, [$r1] ; last_refill_cause = rw_mm_cause
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+
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+3: ; Probably not in a loop, continue normal processing
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#ifdef CONFIG_SMP
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move $s7, $acr ; PGD
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#else
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move.d per_cpu__current_pgd, $acr ; PGD
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#endif
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; Look up PMD in PGD
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- move $s3, $r0 ; rw_mm_cause
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lsrq 24, $r0 ; Get PMD index into PGD (bit 24-31)
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move.d [$acr], $acr ; PGD for the current process
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addi $r0.d, $acr, $acr
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move $s3, $r0 ; rw_mm_cause
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move.d [$acr], $acr ; Get PMD
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- beq 1f
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+ beq 8f
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; Look up PTE in PMD
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lsrq PAGE_SHIFT, $r0
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and.w PAGE_MASK, $acr ; Remove PMD flags
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and.d 0x7ff, $r0 ; Get PTE index into PMD (bit 13-23)
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addi $r0.d, $acr, $acr
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move.d [$acr], $acr ; Get PTE
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- beq 2f
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- move.d [$sp+], $r0 ; Pop r0 in delayslot
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+ beq 9f
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+ movem [$sp], $r2 ; Restore r0-r2 in delay slot
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+ addq 12, $sp
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; Store in TLB
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move $acr, $s5
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- ; Return
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+4: ; Return
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move.d [$sp+], $acr
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- move [$sp], $srs
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+ move [$sp], $srs
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addq 4, $sp
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rete
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rfe
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-1: ; PMD missing, let the mm subsystem fix it up.
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- move.d [$sp+], $r0 ; Pop r0
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-2: ; PTE missing, let the mm subsystem fix it up.
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+
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+5: ; last_refill_cause is invalid
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+ moveq 1, $r2
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+ addq 4, $r1 ; Point to last_refill_cause
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+ move.d $r2, [$acr] ; refill_count = 1
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+ move $s3, $r0 ; Get rw_mm_cause
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+ ba 3b ; Continue normal processing
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+ move.d $r0,[$r1] ; last_refill_cause = rw_mm_cause
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+
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+6: ; rw_mm_cause == last_refill_cause
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+ move.d [$acr], $r2 ; Get refill_count
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+ cmpq 4, $r2 ; refill_count > 4 ?
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+ bhi 7f ; yes
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+ addq 1, $r2 ; refill_count++
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+ ba 3b ; Continue normal processing
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+ move.d $r2, [$acr]
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+
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+7: ; refill_count > 4, error
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+ move.d $acr, $r0 ; Save pointer to refill_count
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+ clear.d [$r0] ; refill_count = 0
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+
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+ ;; rewind the short stack
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+ movem [$sp], $r2 ; Restore r0-r2
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+ addq 12, $sp
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+ move.d [$sp+], $acr
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+ move [$sp], $srs
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+ addq 4, $sp
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+ ;; Keep it simple (slow), save all the regs.
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+ SAVE_ALL
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+ jsr __flush_tlb_all
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+ nop
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+ ba ret_from_intr ; Return
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+ nop
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+
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+8: ; PMD missing, let the mm subsystem fix it up.
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+ movem [$sp], $r2 ; Restore r0-r2
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+9: ; PTE missing, let the mm subsystem fix it up.
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+ addq 12, $sp
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move.d [$sp+], $acr
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- move [$sp], $srs
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+ move [$sp], $srs
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addq 4, $sp
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SAVE_ALL
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move \mmu, $srs
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Jesper Nilsson