CRIS v32: Add workaround for MMU hardware bug for ETRAX FS in mm/mmu.S (3d44305a) · Commits · e / devices / android_kernel_oneplus_sm7250

arch/cris/arch-v32/mm/mmu.S

+81 −12

Original line number	Diff line number	Diff line
		; WARNING : The refill handler has been modified, see below !!!

		/*
		* Copyright (C) 2003 Axis Communications AB
		*
		@@ -61,6 +63,14 @@
		; 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
		@@ -68,6 +78,11 @@
		; 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
		\handler:
		subq 4, $sp
		@@ -76,40 +91,94 @@
		subq 4, $sp
		move \mmu, $srs ; Select MMU support register bank
		move.d $acr, [$sp]
		subq 4, $sp
		move.d $r0, [$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
		#ifdef CONFIG_SMP
		move $s7, $acr ; PGD
		#else
		move.d per_cpu__current_pgd, $acr ; PGD
		#endif
		; Look up PMD in PGD
		move $s3, $r0 ; rw_mm_cause
		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 1f
		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], $acr ; Get PTE
		beq 2f
		move.d [$sp+], $r0 ; Pop r0 in delayslot
		beq 9f
		movem [$sp], $r2 ; Restore r0-r2 in delay slot
		addq 12, $sp
		; Store in TLB
		move $acr, $s5
		; Return
		4: ; Return
		move.d [$sp+], $acr
		move [$sp], $srs
		addq 4, $sp
		rete
		rfe
		1: ; PMD missing, let the mm subsystem fix it up.
		move.d [$sp+], $r0 ; Pop r0
		2: ; PTE missing, let the mm subsystem fix it up.

		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