nios2: enable instruction/data caches

The caches get initialized on boot and flushed after XIP copy
takes place.

Change-Id: I642a14232835a0cf41e007860f5cdb8a2ade1f50
Signed-off-by: Andrew Boie <[email protected]>

arch/nios2/core/Makefile

@@ -4,6 +4,6 @@ ccflags-y += -I$(srctree)/kernel/microkernel/include
 
 obj-y += reset.o irq_manage.o fatal.o swap.o thread.o \
 	 cpu_idle.o irq_offload.o prep_c.o crt0.o \
-	 exception.o sw_isr_table.o
+	 exception.o sw_isr_table.o cache.o
 
 obj-$(CONFIG_IRQ_OFFLOAD) += irq_offload.o

arch/nios2/core/cache.c

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2016 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <arch/cpu.h>
+#include <misc/__assert.h>
+
+
+/**
+ * Flush the entire instruction cache and pipeline.
+ *
+ * You will need to call this function if the application writes new program
+ * text to memory, such as a boot copier or runtime synthesis of code.  If the
+ * new text was written with instructions that do not bypass cache memories,
+ * this should immediately be followed by an invocation of
+ * _nios2_dcache_flush_all() so that cached instruction data is committed to
+ * RAM.
+ *
+ * See Chapter 9 of the Nios II Gen 2 Software Developer's Handbook for more
+ * information on cache considerations.
+ */
+#if NIOS2_ICACHE_SIZE > 0
+void _nios2_icache_flush_all(void)
+{
+	uint32_t i;
+
+	for (i = 0; i < NIOS2_ICACHE_SIZE; i += NIOS2_ICACHE_LINE_SIZE) {
+		_nios2_icache_flush(i);
+	}
+
+	/* Get rid of any stale instructions in the pipeline */
+	_nios2_pipeline_flush();
+}
+#endif
+
+/**
+ * Flush the entire data cache.
+ *
+ * This will be typically needed after writing new program text to memory
+ * after flushing the instruction cache.
+ *
+ * The Nios II does not support hardware cache coherency for multi-master
+ * or multi-processor systems and software coherency must be implemented
+ * when communicating with shared memory. If support for this is introduced
+ * in Zephyr additional APIs for flushing ranges of the data cache will need
+ * to be implemented.
+ *
+ * See Chapter 9 of the Nios II Gen 2 Software Developer's Handbook for more
+ * information on cache considerations.
+ */
+#if NIOS2_DCACHE_SIZE > 0
+void _nios2_dcache_flush_all(void)
+{
+	uint32_t i;
+
+	for (i = 0; i < NIOS2_DCACHE_SIZE; i += NIOS2_DCACHE_LINE_SIZE) {
+		_nios2_dcache_flush(i);
+	}
+}
+#endif

arch/nios2/core/crt0.S

@@ -31,6 +31,7 @@ GTEXT(_interrupt_stack)
 	 */
 	.set noat
 
+
 #if CONFIG_INCLUDE_RESET_VECTOR
 /*
  * Reset vector entry point into the system. Placed into special 'reset'
@@ -42,15 +43,39 @@ GTEXT(_interrupt_stack)
  */
 SECTION_FUNC(reset, __reset)
 
-	/* TODO initialize instruction cache, if present
-	 * ZEP-275
+#if NIOS2_ICACHE_SIZE > 0
+	/* Aside from the instruction cache line associated with the reset
+	 * vector, the contents of the cache memories are indeterminate after
+	 * reset. To ensure cache coherency after reset, the reset handler
+	 * located at the reset vector must immediately initialize the
+	 * instruction cache. Next, either the reset handler or a subsequent
+	 * routine should proceed to initialize the data cache.
+	 *
+	 * The cache memory sizes are *always* a power of 2.
+	 */
+#if NIOS2_ICACHE_SIZE > 0x8000
+	movhi r2, %hi(NIOS2_ICACHE_SIZE)
+#else
+	movui r2, NIOS2_ICACHE_SIZE
+#endif
+0:
+	/* If ECC present, need to execute initd for each word address
+	 * to ensure ECC parity bits in data RAM get initialized
 	 */
+#if NIOS2_ECC_PRESENT
+	subi r2, r2, 4
+#else
+	subi r2, r2, NIOS2_ICACHE_LINE_SIZE
+#endif
+	initi r2
+	bgt r2, zero, 0b
+#endif /* NIOS2_ICACHE_SIZE > 0 */
 
 	/* Done all we need to do here, jump to __text_start */
 	movhi r1, %hi(__start)
 	ori r1, r1, %lo(__start)
 	jmp r1
-#endif
+#endif /* CONFIG_INCLUDE_RESET_VECTOR */
 
 /* Remainder of asm-land initialization code before we can jump into
  * the C domain
@@ -61,9 +86,29 @@ SECTION_FUNC(TEXT, __start)
 	 * ZEP-258
 	 */
 
-	/* TODO initialize data cache, if present
-	 * ZEP-275
+	/* Initialize the data cache if booting from bare metal. If
+	 * we're not booting from our reset vector, either by a bootloader
+	 * or JTAG, assume caches already initialized.
+	 */
+#if NIOS2_DCACHE_SIZE > 0 && defined(CONFIG_INCLUDE_RESET_VECTOR)
+	/* Per documentation data cache size is always a power of two. */
+#if NIOS2_DCACHE_SIZE > 0x8000
+	movhi r2, %hi(NIOS2_DCACHE_SIZE)
+#else
+	movui r2, NIOS2_DCACHE_SIZE
+#endif
+0:
+	/* If ECC present, need to execute initd for each word address
+	 * to ensure ECC parity bits in data RAM get initialized
 	 */
+#if NIOS2_ECC_PRESENT
+	subi r2, r2, 4
+#else
+	subi r2, r2, NIOS2_DCACHE_LINE_SIZE
+#endif
+	initd 0(r2)
+	bgt r2, zero, 0b
+#endif /* NIOS2_DCACHE_SIZE && defined(CONFIG_INCLUDE_RESET_VECTOR) */
 
 #ifdef CONFIG_INIT_STACKS
 	/* Pre-populate all bytes in _interrupt_stack with 0xAA */

arch/nios2/core/prep_c.c

@@ -29,6 +29,7 @@
 #include <stdint.h>
 #include <toolchain.h>
 #include <linker-defs.h>
+#include <nano_private.h>
 
 /**
  *
@@ -68,6 +69,18 @@ static void dataCopy(void)
 	for (n = 0; n < (unsigned int)&__data_num_words; n++) {
 		pRAM[n] = pROM[n];
 	}
+
+	/* In most XIP scenarios we copy the exception code into RAM, so need
+	 * to flush instruction cache.
+	 */
+	_nios2_icache_flush_all();
+#if NIOS2_ICACHE_SIZE > 0
+	/* Only need to flush the data cache here if there actually is an
+	 * instruction cache, so that the cached instruction data written is
+	 * actually committed.
+	 */
+	_nios2_dcache_flush_all();
+#endif
 }
 #else
 static void dataCopy(void)

arch/nios2/include/nano_private.h

@@ -200,6 +200,18 @@ static ALWAYS_INLINE int _IS_IN_ISR(void)
 void _irq_do_offload(void);
 #endif
 
+#if NIOS2_ICACHE_SIZE > 0
+void _nios2_icache_flush_all(void);
+#else
+#define _nios2_icache_flush_all() do { } while (0)
+#endif
+
+#if NIOS2_DCACHE_SIZE > 0
+void _nios2_dcache_flush_all(void);
+#else
+#define _nios2_dcache_flush_all() do { } while (0)
+#endif
+
 #endif /* _ASMLANGUAGE */
 
 #endif /* _NANO_PRIVATE_H */

include/arch/nios2/nios2.h

@@ -94,6 +94,28 @@ static inline void _nios2_report_stack_overflow(void)
 	__asm__ volatile("break 3");
 }
 
+/*
+ * Low-level cache management functions
+ */
+static inline void _nios2_dcache_addr_flush(void *addr)
+{
+	__asm__ volatile ("flushda (%0)" :: "r" (addr));
+}
+
+static inline void _nios2_dcache_flush(uint32_t offset)
+{
+	__asm__ volatile ("flushd (%0)" :: "r" (offset));
+}
+
+static inline void _nios2_icache_flush(uint32_t offset)
+{
+	__asm__ volatile ("flushi %0" :: "r" (offset));
+}
+
+static inline void _nios2_pipeline_flush(void)
+{
+	__asm__ volatile ("flushp");
+}
 
 /*
  * Functions for reading/writing control registers