From c09d29057ab0b04db0857d319c6bff74de31b9c3 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Sat, 9 Apr 2016 13:53:48 +0200 Subject: 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 Acked-by: Masahiro Yamada --- arch/arm/cpu/armv7/cache_v7_asm.S | 84 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 arch/arm/cpu/armv7/cache_v7_asm.S (limited to 'arch/arm/cpu/armv7/cache_v7_asm.S') 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 0000000000..2e4629f927 --- /dev/null +++ b/arch/arm/cpu/armv7/cache_v7_asm.S @@ -0,0 +1,84 @@ +/* + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include +#include +#include +#include + +#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) -- cgit