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 --- Changes in v2: -Remove "Copyright (C) 2012-2015 Masahiro Yamada" from the header -Move the v7_flush_dcache_all asm code from arch/arm/mach-uniphier/arm32/lowlevel_init.S to arch/arm/cpu/armv7/cache_v7_asm.S instead of adding a second copy --- arch/arm/cpu/armv7/Makefile | 2 +- arch/arm/cpu/armv7/cache_v7.c | 41 ++------------ arch/arm/cpu/armv7/cache_v7_asm.S | 84 ++++++++++++++++++++++++++++ arch/arm/mach-uniphier/arm32/lowlevel_init.S | 67 +--------------------- 4 files changed, 92 insertions(+), 102 deletions(-) create mode 100644 arch/arm/cpu/armv7/cache_v7_asm.S

diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile index 45f346c..328c4b1 100644 --- a/arch/arm/cpu/armv7/Makefile +++ b/arch/arm/cpu/armv7/Makefile @@ -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 diff --git a/arch/arm/cpu/armv7/cache_v7.c b/arch/arm/cpu/armv7/cache_v7.c index 94ff488..dd07ba1 100644 --- a/arch/arm/cpu/armv7/cache_v7.c +++ b/arch/arm/cpu/armv7/cache_v7.c @@ -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(); } diff --git a/arch/arm/cpu/armv7/cache_v7_asm.S b/arch/arm/cpu/armv7/cache_v7_asm.S new file mode 100644 index 0000000..2e4629f --- /dev/null +++ b/arch/arm/cpu/armv7/cache_v7_asm.S @@ -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) diff --git a/arch/arm/mach-uniphier/arm32/lowlevel_init.S b/arch/arm/mach-uniphier/arm32/lowlevel_init.S index dd03ad8..e2bb1fc 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)