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Commit c0c3e816 authored by Haavard Skinnemoen's avatar Haavard Skinnemoen
Browse files

[AVR32] Optimize the TLB miss handler 



Reorder some instructions and change the register usage to reduce
the number of pipeline stalls. Also use the bfextu and bfins
instructions for bitfield manipulations instead of shifting and
masking.

This makes gzipping a 80MB file approximately 2% faster.

Signed-off-by: default avatarHaavard Skinnemoen <hskinnemoen@atmel.com>
parent 9ca20a83

arch/avr32/kernel/entry-avr32b.S

+24 −30
Original line number Diff line number Diff line
@@ -100,55 +100,49 @@ dtlb_miss_write: 


	.global	tlb_miss_common

tlb_miss_common:

	mfsr	r0, SYSREG_PTBR

	mfsr	r1, SYSREG_TLBEAR

	mfsr	r0, SYSREG_TLBEAR

	mfsr	r1, SYSREG_PTBR



	/* Is it the vmalloc space? */

	bld	r1, 31

	bld	r0, 31

	brcs	handle_vmalloc_miss



	/* First level lookup */

pgtbl_lookup:

	lsr	r2, r1, PGDIR_SHIFT

	ld.w	r0, r0[r2 << 2]

	bld	r0, _PAGE_BIT_PRESENT

	lsr	r2, r0, PGDIR_SHIFT

	ld.w	r3, r1[r2 << 2]

	bfextu	r1, r0, PAGE_SHIFT, PGDIR_SHIFT - PAGE_SHIFT

	bld	r3, _PAGE_BIT_PRESENT

	brcc	page_table_not_present



	/* TODO: Check access rights on page table if necessary */



	/* Translate to virtual address in P1. */

	andl	r0, 0xf000

	sbr	r0, 31

	andl	r3, 0xf000

	sbr	r3, 31



	/* Second level lookup */

	lsl	r1, (32 - PGDIR_SHIFT)

	lsr	r1, (32 - PGDIR_SHIFT) + PAGE_SHIFT

	add	r2, r0, r1 << 2

	ld.w	r1, r2[0]

	bld	r1, _PAGE_BIT_PRESENT

	ld.w	r2, r3[r1 << 2]

	mfsr	r0, SYSREG_TLBARLO

	bld	r2, _PAGE_BIT_PRESENT

	brcc	page_not_present



	/* Mark the page as accessed */

	sbr	r1, _PAGE_BIT_ACCESSED

	st.w	r2[0], r1

	sbr	r2, _PAGE_BIT_ACCESSED

	st.w	r3[r1 << 2], r2



	/* Drop software flags */

	andl	r1, _PAGE_FLAGS_HARDWARE_MASK & 0xffff

	mtsr	SYSREG_TLBELO, r1

	andl	r2, _PAGE_FLAGS_HARDWARE_MASK & 0xffff

	mtsr	SYSREG_TLBELO, r2



	/* Figure out which entry we want to replace */

	mfsr	r0, SYSREG_TLBARLO

	mfsr	r1, SYSREG_MMUCR

	clz	r2, r0

	brcc	1f

	mov	r1, -1			/* All entries have been accessed, */

	mtsr	SYSREG_TLBARLO, r1	/* so reset TLBAR */

	mov	r2, 0			/* and start at 0 */

1:	mfsr	r1, SYSREG_MMUCR

	lsl	r2, 14

	andl	r1, 0x3fff, COH

	or	r1, r2

	mtsr	SYSREG_MMUCR, r1

	mov	r3, -1			/* All entries have been accessed, */

	mov	r2, 0			/* so start at 0 */

	mtsr	SYSREG_TLBARLO, r3	/* and reset TLBAR */



1:	bfins	r1, r2, SYSREG_DRP_OFFSET, SYSREG_DRP_SIZE

	mtsr	SYSREG_MMUCR, r1

	tlbw



	tlbmiss_restore
@@ -156,8 +150,8 @@ pgtbl_lookup: 


handle_vmalloc_miss:

	/* Simply do the lookup in init's page table */

	mov	r0, lo(swapper_pg_dir)

	orh	r0, hi(swapper_pg_dir)

	mov	r1, lo(swapper_pg_dir)

	orh	r1, hi(swapper_pg_dir)

	rjmp	pgtbl_lookup