MIPS: cache: reimplement dcache_[status, enable, disable]

Those functions are not needed during cache init and can be
implemented in C. Only support the safe disabling of caches when
this is required for booting an OS. Reenabling caches is much
harder to implement if an optional coherency manager must be
supported. As there is no real use-case anyway, dcache_enable
is implemented with an error message.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

arch/mips/lib/cache.c

@@ -175,3 +175,23 @@ void invalidate_dcache_range(ulong start_addr, ulong stop)
 	/* ensure cache ops complete before any further memory accesses */
 	sync();
 }
+
+int dcache_status(void)
+{
+	unsigned int cca = read_c0_config() & CONF_CM_CMASK;
+	return cca != CONF_CM_UNCACHED;
+}
+
+void dcache_enable(void)
+{
+	puts("Not supported!\n");
+}
+
+void dcache_disable(void)
+{
+	/* change CCA to uncached */
+	change_c0_config(CONF_CM_CMASK, CONF_CM_UNCACHED);
+
+	/* ensure the pipeline doesn't contain now-invalid instructions */
+	instruction_hazard_barrier();
+}

arch/mips/lib/cache_init.S

@@ -423,49 +423,3 @@ return:
 	sync
 	jr	ra
 	END(mips_cache_reset)
-
-/*
- * dcache_status - get cache status
- *
- * RETURNS: 0 - cache disabled; 1 - cache enabled
- *
- */
-LEAF(dcache_status)
-	mfc0	t0, CP0_CONFIG
-	li	t1, CONF_CM_UNCACHED
-	andi	t0, t0, CONF_CM_CMASK
-	move	v0, zero
-	beq	t0, t1, 2f
-	li	v0, 1
-2:	jr	ra
-	END(dcache_status)
-
-/*
- * dcache_disable - disable cache
- *
- * RETURNS: N/A
- *
- */
-LEAF(dcache_disable)
-	mfc0	t0, CP0_CONFIG
-	li	t1, -8
-	and	t0, t0, t1
-	ori	t0, t0, CONF_CM_UNCACHED
-	mtc0	t0, CP0_CONFIG
-	jr	ra
-	END(dcache_disable)
-
-/*
- * dcache_enable - enable cache
- *
- * RETURNS: N/A
- *
- */
-LEAF(dcache_enable)
-	mfc0	t0, CP0_CONFIG
-	ori	t0, CONF_CM_CMASK
-	xori	t0, CONF_CM_CMASK
-	ori	t0, CONFIG_SYS_MIPS_CACHE_MODE
-	mtc0	t0, CP0_CONFIG
-	jr	ra
-	END(dcache_enable)