init_rom: Add init_rom layer

Create a thin init_rom layer for accessing data objects linked into the
.init_rom section with the CONFIG_CHIP_INIT_ROM_REGION opton and
__init_rom attribute.

BUG=b:160330682
BRANCH=none
TEST=make buildall
TEST=Using the next CL, verify BMI260 config data can be read using both
memory mapped and indirect access.

Signed-off-by: Keith Short <keithshort@chromium.org>
Change-Id: I6cd311637e87cd10ac394ff75c4bfc16bbade3b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2335739
Reviewed-by: caveh jalali <caveh@chromium.org>
Reviewed-by: Abe Levkoy <alevkoy@chromium.org>
Commit-Queue: caveh jalali <caveh@chromium.org>

2 files changed, 70 insertions, 1 deletions

diff --git a/common/build.mk b/common/build.mk
index 8a2cd33cbd..0a7fbe86cc 100644
--- a/common/build.mk
+++ b/common/build.mk
@@ -56,7 +56,7 @@ common-$(CONFIG_CMD_I2CWEDGE)+=i2c_wedge.o
 common-$(CONFIG_COMMON_GPIO)+=gpio.o gpio_commands.o
 common-$(CONFIG_IO_EXPANDER)+=ioexpander.o
 common-$(CONFIG_COMMON_PANIC_OUTPUT)+=panic_output.o
-common-$(CONFIG_COMMON_RUNTIME)+=hooks.o main.o system.o peripheral.o
+common-$(CONFIG_COMMON_RUNTIME)+=hooks.o main.o system.o peripheral.o init_rom.o
 common-$(CONFIG_COMMON_TIMER)+=timer.o
 common-$(CONFIG_CRC8)+= crc8.o
 common-$(CONFIG_CURVE25519)+=curve25519.o
diff --git a/common/init_rom.c b/common/init_rom.c
new file mode 100644
index 0000000000..fd796f7fe9
--- /dev/null
+++ b/common/init_rom.c
@@ -0,0 +1,69 @@
+/* Copyright 2020 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* Init ROM module for Chrome EC */
+
+#include "builtin/assert.h"
+#include "common.h"
+#include "init_rom.h"
+#include "flash.h"
+#include "stdbool.h"
+#include "stddef.h"
+
+const void *init_rom_map(const void *addr, int size)
+{
+	const char *src;
+	uintptr_t offset;
+
+	/*
+	 * When CONFIG_CHIP_INIT_ROM_REGION isn't enabled, .init_rom objects
+	 * are linked into the .rodata section and directly addressable.
+	 * Return the caller's pointer.
+	 */
+	if (!IS_ENABLED(CONFIG_CHIP_INIT_ROM_REGION))
+		return addr;
+
+	/*
+	 * When flash isn't memory mapped, caller's must use init_rom_copy()
+	 * to copy .init_rom data into RAM.
+	 */
+	if (!IS_ENABLED(CONFIG_MAPPED_STORAGE))
+		return NULL;
+
+	/*
+	 * Safe pointer conversion - needed for host tests which can have
+	 * 64-bit pointers.
+	 */
+	offset = (uintptr_t)addr;
+
+	ASSERT(offset <= __INT_MAX__);
+
+	/*
+	 * Convert flash offset to memory mapped address
+	 */
+	if (flash_dataptr((int)offset, size, 1, &src) < 0)
+		return NULL;
+
+	/* Once the flash offset is validated, lock the flash for the caller */
+	flash_lock_mapped_storage(1);
+
+	return src;
+}
+
+/*
+ * The addr and size parameters are provided for forward compatibility if
+ * the flash API is extended to support locking less than the entire flash.
+ */
+void init_rom_unmap(const void *addr, int size)
+{
+	if (IS_ENABLED(CONFIG_CHIP_INIT_ROM_REGION))
+		flash_lock_mapped_storage(0);
+}
+
+int init_rom_copy(int offset, int size, char *data)
+{
+	return flash_read(offset, size, data);
+}
+