arc: significant cache rework

[1] Align cache management functions to those in Linux kernel. I.e.:
    a) Use the same functions for all cache ops (D$ Inv/Flush)
    b) Split cache ops in 3 sub-functions: "before", "lineloop" and
"after". That way we may re-use "before" and "after" functions for
region and full cache ops.

 [2] Implement full-functional L2 (SLC) management. Before SLC was
simply disabled early on boot. It's also possible to enable or disable
L2 cache from config utility.

 [3] Disable/enable corresponding caches early on boot. So if U-Boot is
configured to use caches they will be used at all times (this is useful
in partucular for speed-up of relocation).

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
diff --git a/arch/arc/lib/start.S b/arch/arc/lib/start.S
index e1ef19c..26a5934 100644
--- a/arch/arc/lib/start.S
+++ b/arch/arc/lib/start.S
@@ -13,18 +13,46 @@
 	/* Setup interrupt vector base that matches "__text_start" */
 	sr	__ivt_start, [ARC_AUX_INTR_VEC_BASE]
 
-	/* Setup stack- and frame-pointers */
-	mov	%sp, CONFIG_SYS_INIT_SP_ADDR
-	mov	%fp, %sp
+	; Disable/enable I-cache according to configuration
+	lr	r5, [ARC_BCR_IC_BUILD]
+	breq	r5, 0, 1f		; I$ doesn't exist
+	lr	r5, [ARC_AUX_IC_CTRL]
+#ifndef CONFIG_SYS_ICACHE_OFF
+	bclr	r5, r5, 0		; 0 - Enable, 1 is Disable
+#else
+	bset	r5, r5, 0		; I$ exists, but is not used
+#endif
+	sr	r5, [ARC_AUX_IC_CTRL]
+
+1:
+	; Disable/enable D-cache according to configuration
+	lr	r5, [ARC_BCR_DC_BUILD]
+	breq	r5, 0, 1f		; D$ doesn't exist
+	lr	r5, [ARC_AUX_DC_CTRL]
+	bclr	r5, r5, 6		; Invalidate (discard w/o wback)
+#ifndef CONFIG_SYS_DCACHE_OFF
+	bclr	r5, r5, 0		; Enable (+Inv)
+#else
+	bset	r5, r5, 0		; Disable (+Inv)
+#endif
+	sr	r5, [ARC_AUX_DC_CTRL]
 
-	/* Unconditionally disable caches */
+1:
 #ifdef CONFIG_ISA_ARCV2
-	bl	slc_flush
-	bl	slc_disable
+	; Disable System-Level Cache (SLC)
+	lr	r5, [ARC_BCR_SLC]
+	breq	r5, 0, 1f		; SLC doesn't exist
+	lr	r5, [ARC_AUX_SLC_CTRL]
+	bclr	r5, r5, 6		; Invalidate (discard w/o wback)
+	bclr	r5, r5, 0		; Enable (+Inv)
+	sr	r5, [ARC_AUX_SLC_CTRL]
+
+1:
 #endif
-	bl	flush_dcache_all
-	bl	dcache_disable
-	bl	icache_disable
+
+	/* Setup stack- and frame-pointers */
+	mov	%sp, CONFIG_SYS_INIT_SP_ADDR
+	mov	%fp, %sp
 
 	/* Allocate and zero GD, update SP */
 	mov	%r0, %sp