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>
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 @@
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 @@
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 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)