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arm: Replace v7_maint_dcache_all(ARMV7_DCACHE_CLEAN_INVAL_ALL) with asm code

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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>
This commit is contained in:
Hans de Goede 2016-04-09 13:53:48 +02:00 • committed by Tom Rini
parent 456ecd08ec
commit c09d29057a
4 changed files with 92 additions and 102 deletions
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2
arch/arm/cpu/armv7/Makefile
View file

@ -7,7 +7,7 @@
extra-y := start.o
obj-y += cache_v7.o
obj-y += cache_v7.o cache_v7_asm.o
obj-y += cpu.o cp15.o
obj-y += syslib.o

41
arch/arm/cpu/armv7/cache_v7.c
View file

@ -16,6 +16,10 @@
#define ARMV7_DCACHE_CLEAN_INVAL_RANGE 4
#ifndef CONFIG_SYS_DCACHE_OFF
/* Asm functions from cache_v7_asm.S */
void v7_flush_dcache_all(void);
static int check_cache_range(unsigned long start, unsigned long stop)
{
int ok = 1;
@ -88,34 +92,6 @@ static void v7_inval_dcache_level_setway(u32 level, u32 num_sets,
DSB;
}
static void v7_clean_inval_dcache_level_setway(u32 level, u32 num_sets,
u32 num_ways, u32 way_shift,
u32 log2_line_len)
{
int way, set;
u32 setway;
/*
* For optimal assembly code:
* a. count down
* b. have bigger loop inside
*/
for (way = num_ways - 1; way >= 0 ; way--) {
for (set = num_sets - 1; set >= 0; set--) {
setway = (level << 1) | (set << log2_line_len) |
(way << way_shift);
/*
* Clean & Invalidate data/unified
* cache line by set/way
*/
asm volatile (" mcr p15, 0, %0, c7, c14, 2"
: : "r" (setway));
}
}
/* DSB to make sure the operation is complete */
DSB;
}
static void v7_maint_dcache_level_setway(u32 level, u32 operation)
{
u32 ccsidr;
@ -142,13 +118,8 @@ static void v7_maint_dcache_level_setway(u32 level, u32 operation)
log2_num_ways = log_2_n_round_up(num_ways);
way_shift = (32 - log2_num_ways);
if (operation == ARMV7_DCACHE_INVAL_ALL) {
v7_inval_dcache_level_setway(level, num_sets, num_ways,
v7_inval_dcache_level_setway(level, num_sets, num_ways,
way_shift, log2_line_len);
} else if (operation == ARMV7_DCACHE_CLEAN_INVAL_ALL) {
v7_clean_inval_dcache_level_setway(level, num_sets, num_ways,
way_shift, log2_line_len);
}
}
static void v7_maint_dcache_all(u32 operation)
@ -263,7 +234,7 @@ void invalidate_dcache_all(void)
*/
void flush_dcache_all(void)
{
v7_maint_dcache_all(ARMV7_DCACHE_CLEAN_INVAL_ALL);
v7_flush_dcache_all();
v7_outer_cache_flush_all();
}

84
arch/arm/cpu/armv7/cache_v7_asm.S Normal file
View file

@ -0,0 +1,84 @@
/*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <config.h>
#include <linux/linkage.h>
#include <linux/sizes.h>
#include <asm/system.h>
#ifdef CONFIG_SYS_THUMB_BUILD
#define ARM(x...)
#define THUMB(x...) x
#else
#define ARM(x...) x
#define THUMB(x...)
#endif
/*
* v7_flush_dcache_all()
*
* Flush the whole D-cache.
*
* Corrupted registers: r0-r7, r9-r11 (r6 only in Thumb mode)
*
* 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
bx lr
ENDPROC(__v7_flush_dcache_all)
ENTRY(v7_flush_dcache_all)
ARM( stmfd sp!, {r4-r5, r7, r9-r11, lr} )
THUMB( stmfd sp!, {r4-r7, r9-r11, lr} )
bl __v7_flush_dcache_all
ARM( ldmfd sp!, {r4-r5, r7, r9-r11, lr} )
THUMB( ldmfd sp!, {r4-r7, r9-r11, lr} )
bx lr
ENDPROC(v7_flush_dcache_all)

67
arch/arm/mach-uniphier/arm32/lowlevel_init.S
View file

@ -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)