Initial import

1 files changed, 210 insertions, 0 deletions

diff --git a/arch/cris/arch-v32/mm/mmu.S b/arch/cris/arch-v32/mm/mmu.S
new file mode 100644
index 000000000..c0981044e
--- /dev/null
+++ b/arch/cris/arch-v32/mm/mmu.S
@@ -0,0 +1,210 @@
+; WARNING : The refill handler has been modified, see below !!!
+
+/*
+ *  Copyright (C) 2003 Axis Communications AB
+ *
+ *  Authors:	Mikael Starvik (starvik@axis.com)
+ *
+ * Code for the fault low-level handling routines.
+ *
+ */
+
+#include <asm/page.h>
+#include <asm/pgtable.h>
+
+; Save all register. Must save in same order as struct pt_regs.
+.macro SAVE_ALL
+	subq	12, $sp
+	move	$erp, [$sp]
+	subq	4, $sp
+	move	$srp, [$sp]
+	subq	4, $sp
+	move	$ccs, [$sp]
+	subq	4, $sp
+	move	$spc, [$sp]
+	subq	4, $sp
+	move	$mof, [$sp]
+	subq	4, $sp
+	move	$srs, [$sp]
+	subq	4, $sp
+	move.d	$acr, [$sp]
+	subq	14*4, $sp
+	movem	$r13, [$sp]
+	subq	4, $sp
+	move.d	$r10, [$sp]
+.endm
+
+; Bus fault handler. Extracts relevant information and calls mm subsystem
+; to handle the fault.
+.macro	MMU_BUS_FAULT_HANDLER handler, mmu, we, ex
+	.globl	\handler
+	.type   \handler,"function"
+\handler:
+	SAVE_ALL
+	move	\mmu, $srs	; Select MMU support register bank
+	move.d  $sp, $r11	; regs
+	moveq	1, $r12		; protection fault
+	moveq   \we, $r13	; write exception?
+	orq	\ex << 1, $r13	; execute?
+	move    $s3, $r10	; rw_mm_cause
+	and.d	~8191, $r10	; Get faulting page start address
+
+	jsr	do_page_fault
+	nop
+	ba	ret_from_intr
+	nop
+	.size   \handler, . - \handler
+.endm
+
+; Refill handler. Three cases may occur:
+;   1. PMD and PTE exists in mm subsystem but not in TLB
+;   2. PMD exists but not PTE
+;   3. PMD doesn't exist
+; The code below handles case 1 and calls the mm subsystem for case 2 and 3.
+; Do not touch this code without very good reasons and extensive testing.
+; Note that the code is optimized to minimize stalls (makes the code harder
+; to read).
+;
+; WARNING !!!
+; Modified by Mikael Asker 060725: added a workaround for strange TLB
+; behavior. If the same PTE is present in more than one set, the TLB
+; doesn't recognize it and we get stuck in a loop of refill exceptions.
+; The workaround detects such loops and exits them by flushing
+; the TLB contents. The problem and workaround were verified
+; in VCS by Mikael Starvik.
+;
+; Each page is 8 KB. Each PMD holds 8192/4 PTEs (each PTE is 4 bytes) so each
+; PMD holds 16 MB of virtual memory.
+;   Bits  0-12 : Offset within a page
+;   Bits 13-23 : PTE offset within a PMD
+;   Bits 24-31 : PMD offset within the PGD
+
+.macro MMU_REFILL_HANDLER handler, mmu
+	.data
+1:	.dword	0		; refill_count
+                                ;   == 0 <=> last_refill_cause is invalid
+2:	.dword	0		; last_refill_cause
+	.text
+	.globl \handler
+	.type   \handler, "function"
+\handler:
+	subq	4, $sp
+; (The pipeline stalls for one cycle; $sp used as address in the next cycle.)
+	move	$srs, [$sp]
+	subq	4, $sp
+	move	\mmu, $srs	; Select MMU support register bank
+	move.d	$acr, [$sp]
+	subq	12, $sp
+	move.d	1b, $acr        ; Point to refill_count
+	movem	$r2, [$sp]
+
+	test.d	[$acr]	        ; refill_count == 0 ?
+	beq	5f		;   yes, last_refill_cause is invalid
+        move.d	$acr, $r1
+
+	; last_refill_cause is valid, investigate cause
+        addq    4, $r1          ; Point to last_refill_cause
+	move	$s3, $r0	; Get rw_mm_cause
+	move.d	[$r1], $r2	; Get last_refill_cause
+	cmp.d	$r0, $r2	; rw_mm_cause == last_refill_cause ?
+	beq	6f		;   yes, increment count
+	moveq	1, $r2
+
+        ; rw_mm_cause != last_refill_cause
+	move.d	$r2, [$acr]	; refill_count = 1
+	move.d	$r0, [$r1]	; last_refill_cause = rw_mm_cause
+
+3:	; Probably not in a loop, continue normal processing
+	move.d  current_pgd, $acr ; PGD
+	; Look up PMD in PGD
+	lsrq	24, $r0	; Get PMD index into PGD (bit 24-31)
+	move.d  [$acr], $acr	; PGD for the current process
+	addi	$r0.d, $acr, $acr
+	move	$s3, $r0	; rw_mm_cause
+	move.d  [$acr], $acr	; Get PMD
+	beq	8f
+	; Look up PTE in PMD
+	lsrq	PAGE_SHIFT, $r0
+	and.w	PAGE_MASK, $acr	; Remove PMD flags
+	and.d	0x7ff, $r0	; Get PTE index into PMD (bit 13-23)
+	addi    $r0.d, $acr, $acr
+	move.d  [$acr], $acr	; Get PTE
+	beq	9f
+	movem	[$sp], $r2	; Restore r0-r2 in delay slot
+	addq	12, $sp
+	; Store in TLB
+	move	$acr, $s5
+4:	; Return
+	move.d	[$sp+], $acr
+	move	[$sp], $srs
+	addq	4, $sp
+	rete
+	rfe
+
+5:      ; last_refill_cause is invalid
+	moveq	1, $r2
+        addq    4, $r1          ; Point to last_refill_cause
+	move.d	$r2, [$acr]	; refill_count = 1
+	move	$s3, $r0	; Get rw_mm_cause
+        ba      3b		; Continue normal processing
+	move.d	$r0,[$r1]	; last_refill_cause = rw_mm_cause
+
+6:      ; rw_mm_cause == last_refill_cause
+        move.d  [$acr], $r2     ; Get refill_count
+	cmpq	4, $r2		; refill_count > 4 ?
+	bhi	7f		;   yes
+	addq	1, $r2	        ; refill_count++
+	ba	3b		; Continue normal processing
+	move.d	$r2, [$acr]
+
+7:	; refill_count > 4, error
+	move.d	$acr, $r0       ; Save pointer to refill_count
+	clear.d	[$r0]		; refill_count = 0
+
+	;; rewind the short stack
+	movem	[$sp], $r2	; Restore r0-r2
+	addq	12, $sp
+	move.d	[$sp+], $acr
+	move	[$sp], $srs
+	addq	4, $sp
+	;; Keep it simple (slow), save all the regs.
+	SAVE_ALL
+	jsr	__flush_tlb_all
+	nop
+	ba	ret_from_intr	; Return
+	nop
+
+8:	; PMD missing, let the mm subsystem fix it up.
+	movem	[$sp], $r2	; Restore r0-r2
+9:      ; PTE missing, let the mm subsystem fix it up.
+	addq	12, $sp
+	move.d	[$sp+], $acr
+	move	[$sp], $srs
+	addq	4, $sp
+	SAVE_ALL
+	move    \mmu, $srs
+	move.d	$sp, $r11	; regs
+	clear.d	$r12		; Not a protection fault
+	move.w  PAGE_MASK, $acr
+	move    $s3, $r10	; rw_mm_cause
+	btstq   9, $r10		; Check if write access
+	smi     $r13
+	and.w	PAGE_MASK, $r10	; Get VPN (virtual address)
+	jsr	do_page_fault
+	and.w   $acr, $r10
+	; Return
+	ba	ret_from_intr
+	nop
+	.size   \handler, . - \handler
+.endm
+
+	; This is the MMU bus fault handlers.
+
+MMU_REFILL_HANDLER i_mmu_refill, 1
+MMU_BUS_FAULT_HANDLER i_mmu_invalid, 1, 0, 0
+MMU_BUS_FAULT_HANDLER i_mmu_access,  1, 0, 0
+MMU_BUS_FAULT_HANDLER i_mmu_execute, 1, 0, 1
+MMU_REFILL_HANDLER d_mmu_refill,  2
+MMU_BUS_FAULT_HANDLER d_mmu_invalid, 2, 0, 0
+MMU_BUS_FAULT_HANDLER d_mmu_access,  2, 0, 0
+MMU_BUS_FAULT_HANDLER d_mmu_write,   2, 1, 0