MIPS: allow systems to skip loads during cache init
Current MIPS systems do not require that loads be performed to force the
parity of cache lines, a simple invalidate by clearing the tag for each
line will suffice. Thus this patch makes the loads & subsequent second
invalidation conditional upon the CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD
option, and defines that for existing mips32 targets. Exceptions are
malta where this is known to be unnecessary, and qemu-mips where caches
are not implemented.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index ef78929..bc4283d 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -36,6 +36,7 @@
select SUPPORTS_BIG_ENDIAN
select SUPPORTS_CPU_MIPS32_R1
select SUPPORTS_CPU_MIPS32_R2
+ select SYS_MIPS_CACHE_INIT_RAM_LOAD
config TARGET_DBAU1X00
bool "Support dbau1x00"
@@ -43,12 +44,14 @@
select SUPPORTS_LITTLE_ENDIAN
select SUPPORTS_CPU_MIPS32_R1
select SUPPORTS_CPU_MIPS32_R2
+ select SYS_MIPS_CACHE_INIT_RAM_LOAD
config TARGET_PB1X00
bool "Support pb1x00"
select SUPPORTS_LITTLE_ENDIAN
select SUPPORTS_CPU_MIPS32_R1
select SUPPORTS_CPU_MIPS32_R2
+ select SYS_MIPS_CACHE_INIT_RAM_LOAD
endchoice
@@ -185,6 +188,9 @@
config SWAP_IO_SPACE
bool
+config SYS_MIPS_CACHE_INIT_RAM_LOAD
+ bool
+
endif
endmenu
diff --git a/arch/mips/lib/cache_init.S b/arch/mips/lib/cache_init.S
index cbd04bd..04a36b2 100644
--- a/arch/mips/lib/cache_init.S
+++ b/arch/mips/lib/cache_init.S
@@ -113,6 +113,8 @@
l1_info t3, t9, MIPS_CONF1_DA_SHIFT
#endif
+#ifdef CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD
+
/* Determine the largest L1 cache size */
#if defined(CONFIG_SYS_ICACHE_SIZE) && defined(CONFIG_SYS_DCACHE_SIZE)
#if CONFIG_SYS_ICACHE_SIZE > CONFIG_SYS_DCACHE_SIZE
@@ -134,14 +136,15 @@
f_fill64 a0, -64, zero
bne a0, a1, 2b
- /*
- * The caches are probably in an indeterminate state,
- * so we force good parity into them by doing an
- * invalidate, load/fill, invalidate for each line.
- */
+#endif /* CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD */
/*
- * Assume bottom of RAM will generate good parity for the cache.
+ * The caches are probably in an indeterminate state, so we force good
+ * parity into them by doing an invalidate for each line. If
+ * CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD is set then we'll proceed to
+ * perform a load/fill & a further invalidate for each line, assuming
+ * that the bottom of RAM (having just been cleared) will generate good
+ * parity for the cache.
*/
/*
@@ -153,12 +156,14 @@
PTR_ADDU t1, t0, t2
/* clear tag to invalidate */
cache_loop t0, t1, t8, INDEX_STORE_TAG_I
+#ifdef CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD
/* fill once, so data field parity is correct */
PTR_LI t0, INDEX_BASE
cache_loop t0, t1, t8, FILL
/* invalidate again - prudent but not strictly neccessary */
PTR_LI t0, INDEX_BASE
cache_loop t0, t1, t8, INDEX_STORE_TAG_I
+#endif
/*
* then initialize D-cache.
@@ -169,6 +174,7 @@
PTR_ADDU t1, t0, t3
/* clear all tags */
cache_loop t0, t1, t9, INDEX_STORE_TAG_D
+#ifdef CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD
/* load from each line (in cached space) */
PTR_LI t0, INDEX_BASE
2: LONG_L zero, 0(t0)
@@ -177,6 +183,7 @@
/* clear all tags */
PTR_LI t0, INDEX_BASE
cache_loop t0, t1, t9, INDEX_STORE_TAG_D
+#endif
3: jr ra
END(mips_cache_reset)