MIPS: cache: optimise changing of k0 CCA mode

Changing the Cache Coherency Algorithm (CCA) for kernel mode
requires executing from KSEG1. Thus do a jump from KSEG0 to KSEG1
before changing the CCA mode. Jump back to KSEG0 afterwards.

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

diff --git a/arch/mips/lib/cache_init.S b/arch/mips/lib/cache_init.S
index 395bfff..4e95603 100644 (file)
--- a/arch/mips/lib/cache_init.S
+++ b/arch/mips/lib/cache_init.S
@@ -84,6 +84,7 @@
 10:
        .set    pop
        .endm
+
 /*
  * mips_cache_reset - low level initialisation of the primary caches
  *
@@ -319,19 +320,21 @@ l1_init:
        PTR_LI          t0, INDEX_BASE
        cache_loop      t0, t1, R_IC_LINE, INDEX_STORE_TAG_I
 #endif
-
-       /* Enable use of the I-cache by setting Config.K0 */
        sync
-       mfc0            t0, CP0_CONFIG
-       li              t1, CONFIG_SYS_MIPS_CACHE_MODE
-#if __mips_isa_rev >= 2
-       ins             t0, t1, 0, 3
-#else
-       ori             t0, t0, CONF_CM_CMASK
-       xori            t0, t0, CONF_CM_CMASK
+
+       /*
+        * Enable use of the I-cache by setting Config.K0. The code for this
+        * must be executed from KSEG1. Jump from KSEG0 to KSEG1 to do this.
+        * Jump back to KSEG0 after caches are enabled and insert an
+        * instruction hazard barrier.
+        */
+       PTR_LA          t0, change_k0_cca
+       li              t1, CPHYSADDR(~0)
+       and             t0, t0, t1
+       PTR_LI          t1, CKSEG1
        or              t0, t0, t1
-#endif
-       mtc0            t0, CP0_CONFIG
+       li              a0, CONFIG_SYS_MIPS_CACHE_MODE
+       jalr.hb         t0
 
        /*
         * then initialize D-cache.
@@ -391,16 +394,9 @@ l2_unbypass:
        beqz            t0, 2f
 
        /* Change Config.K0 to a coherent CCA */
-       mfc0            t0, CP0_CONFIG
-       li              t1, CONF_CM_CACHABLE_COW
-#if __mips_isa_rev >= 2
-       ins             t0, t1, 0, 3
-#else
-       ori             t0, t0, CONF_CM_CMASK
-       xori            t0, t0, CONF_CM_CMASK
-       or              t0, t0, t1
-#endif
-       mtc0            t0, CP0_CONFIG
+       PTR_LA          t0, change_k0_cca
+       li              a0, CONF_CM_CACHABLE_COW
+       jalr            t0
 
        /*
         * Join the coherent domain such that the caches of this core are kept
@@ -421,5 +417,19 @@ l2_unbypass:
 return:
        /* Ensure all cache operations complete before returning */
        sync
-       jr      ra
+       jr      R_RETURN
        END(mips_cache_reset)
+
+LEAF(change_k0_cca)
+       mfc0            t0, CP0_CONFIG
+#if __mips_isa_rev >= 2
+       ins             t0, a0, 0, 3
+#else
+       xor             a0, a0, t0
+       andi            a0, a0, CONF_CM_CMASK
+       xor             a0, a0, t0
+#endif
+       mtc0            a0, CP0_CONFIG
+
+       jr.hb           ra
+       END(change_k0_cca)