arm, at91: add icache support

add at least icache support for at91 based boards.
This speeds up NOR flash access on an at91sam9g15
based board from 15.2 seconds reading 8 MiB from
a SPI NOR flash to 5.7 seconds.

Signed-off-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Andreas Bießmann <andreas@biessmann.org>

arch/arm/mach-at91/arm926ejs/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_AT91SAM9N12)	+= at91sam9n12_devices.o
 obj-$(CONFIG_AT91SAM9X5)	+= at91sam9x5_devices.o
 obj-$(CONFIG_AT91_EFLASH)	+= eflash.o
 obj-$(CONFIG_AT91_LED)	+= led.o
+obj-y += cache.o
 obj-y += clock.o
 obj-y += cpu.o
 obj-y	+= reset.o

arch/arm/mach-at91/arm926ejs/cache.c

@@ -0,0 +1,29 @@
+/*
+ * (C) Copyright 2016
+ * Heiko Schocher, DENX Software Engineering, hs@denx.de.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+#include <linux/types.h>
+#include <common.h>
+
+void enable_caches(void)
+{
+#ifndef CONFIG_SYS_ICACHE_OFF
+	icache_enable();
+#endif
+}
+
+#ifndef CONFIG_SYS_ICACHE_OFF
+/* Invalidate entire I-cache and branch predictor array */
+void invalidate_icache_all(void)
+{
+	unsigned long i = 0;
+
+	asm ("mcr p15, 0, %0, c7, c5, 0" : : "r" (i));
+}
+#else
+void invalidate_icache_all(void)
+{
+}
+#endif

board/bluewater/gurnard/gurnard.c

@@ -414,12 +414,6 @@ void reset_phy(void)
 {
 }
 
-/* This breaks the Ethernet MAC at present */
-void enable_caches(void)
-{
-	dcache_enable();
-}
-
 /* SPI chip select control - only used for FPGA programming */
 #ifdef CONFIG_ATMEL_SPI