arm: Replace v7_maint_dcache_all(ARMV7_DCACHE_CLEAN_INVAL_ALL) with asm code

v7_maint_dcache_all() does not work reliable when build with gcc6,
see: https://bugzilla.redhat.com/show_bug.cgi?id=1318788

While debugging this I learned that v7_maint_dcache_all() is unreliable
when build with gcc5 too when it is marked as noinline.

This commit fixes the reliability issues by replacing the C-code with
the ready to use asm implementation from the kernel.

Given that this code when written as C-code clearly is quite fragile
(also see the existing comments about the C-code being the way it is
 to get optimal assembly) and that we have a proven asm alternative,
I believe that this is the best solution.

Note that we actually already had a copy of the kernel's
v7_flush_dcache_all() before this commit in
arch/arm/mach-uniphier/arm32/lowlevel_init.S.

This commit moves that code arch/arm/cpu/armv7/cache_v7_asm.S, renames
it to __v7_flush_dcache_all(), and adds a v7_flush_dcache_all() wrapper
which saves / restores the clobbered registers for use from C-code.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>

1 files changed, 1 insertions, 66 deletions

diff --git a/arch/arm/mach-uniphier/arm32/lowlevel_init.S b/arch/arm/mach-uniphier/arm32/lowlevel_init.S
index dd03ad8143..e2bb1fcb44 100644
--- a/arch/arm/mach-uniphier/arm32/lowlevel_init.S
+++ b/arch/arm/mach-uniphier/arm32/lowlevel_init.S
@@ -38,7 +38,7 @@ ENTRY(lowlevel_init)
 	 * to do next is to create a page table and switch over to it.
 	 */
 	bl	create_page_table
-	bl	v7_flush_dcache_all
+	bl	__v7_flush_dcache_all
 
 	/* Disable MMU and Dcache before switching Page Table */
 	mrc	p15, 0, r0, c1, c0, 0	@ SCTLR (System Control Register)
@@ -140,68 +140,3 @@ ENTRY(create_page_table)
 	str	r0, [r12, #4]		@ mark the second section as Normal
 	mov	pc, lr
 ENDPROC(create_page_table)
-
-/* We don't use Thumb instructions for now */
-#define ARM(x...)	x
-#define THUMB(x...)
-
-/*
- *	v7_flush_dcache_all()
- *
- *	Flush the whole D-cache.
- *
- *	Corrupted registers: r0-r7, r9-r11 (r6 only in Thumb mode)
- *
- *	- mm    - mm_struct describing address space
- *
- *	Note: copied from arch/arm/mm/cache-v7.S of Linux 4.4
- */
-ENTRY(v7_flush_dcache_all)
-	dmb					@ ensure ordering with previous memory accesses
-	mrc	p15, 1, r0, c0, c0, 1		@ read clidr
-	mov	r3, r0, lsr #23			@ move LoC into position
-	ands	r3, r3, #7 << 1			@ extract LoC*2 from clidr
-	beq	finished			@ if loc is 0, then no need to clean
-start_flush_levels:
-	mov	r10, #0				@ start clean at cache level 0
-flush_levels:
-	add	r2, r10, r10, lsr #1		@ work out 3x current cache level
-	mov	r1, r0, lsr r2			@ extract cache type bits from clidr
-	and	r1, r1, #7			@ mask of the bits for current cache only
-	cmp	r1, #2				@ see what cache we have at this level
-	blt	skip				@ skip if no cache, or just i-cache
-	mcr	p15, 2, r10, c0, c0, 0		@ select current cache level in cssr
-	isb					@ isb to sych the new cssr&csidr
-	mrc	p15, 1, r1, c0, c0, 0		@ read the new csidr
-	and	r2, r1, #7			@ extract the length of the cache lines
-	add	r2, r2, #4			@ add 4 (line length offset)
-	movw	r4, #0x3ff
-	ands	r4, r4, r1, lsr #3		@ find maximum number on the way size
-	clz	r5, r4				@ find bit position of way size increment
-	movw	r7, #0x7fff
-	ands	r7, r7, r1, lsr #13		@ extract max number of the index size
-loop1:
-	mov	r9, r7				@ create working copy of max index
-loop2:
- ARM(	orr	r11, r10, r4, lsl r5	)	@ factor way and cache number into r11
- THUMB(	lsl	r6, r4, r5		)
- THUMB(	orr	r11, r10, r6		)	@ factor way and cache number into r11
- ARM(	orr	r11, r11, r9, lsl r2	)	@ factor index number into r11
- THUMB(	lsl	r6, r9, r2		)
- THUMB(	orr	r11, r11, r6		)	@ factor index number into r11
-	mcr	p15, 0, r11, c7, c14, 2		@ clean & invalidate by set/way
-	subs	r9, r9, #1			@ decrement the index
-	bge	loop2
-	subs	r4, r4, #1			@ decrement the way
-	bge	loop1
-skip:
-	add	r10, r10, #2			@ increment cache number
-	cmp	r3, r10
-	bgt	flush_levels
-finished:
-	mov	r10, #0				@ swith back to cache level 0
-	mcr	p15, 2, r10, c0, c0, 0		@ select current cache level in cssr
-	dsb	st
-	isb
-	mov	pc, lr
-ENDPROC(v7_flush_dcache_all)