zephyr: emul: Implement flash protection

Implement a simple flash protection for RO and ALL.

BRANCH=None
BUG=b:236075598
TEST=The following CL tests the functions.

Change-Id: I0eec87d7ebbf776a676103ae26df5460d3685431
Signed-off-by: Wai-Hong Tam <waihong@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3854310
Reviewed-by: Yuval Peress <peress@google.com>

2 files changed, 72 insertions, 7 deletions

diff --git a/zephyr/emul/emul_flash.c b/zephyr/emul/emul_flash.c
index e3c72c1c3d..49130d2d32 100644
--- a/zephyr/emul/emul_flash.c
+++ b/zephyr/emul/emul_flash.c
@@ -14,6 +14,8 @@ LOG_MODULE_REGISTER(emul_flash);
 #include <drivers/cros_flash.h>
 #include <zephyr/sys/__assert.h>
 
+#include "flash.h"
+
 struct flash_emul_data {};
 
 struct flash_emul_cfg {
@@ -21,6 +23,9 @@ struct flash_emul_cfg {
 	struct flash_emul_data *data;
 };
 
+/* Variables to emulate the protection */
+bool ro_protected, all_protected;
+
 void system_jump_to_booter(void)
 {
 }
@@ -60,26 +65,66 @@ static int cros_flash_emul_erase(const struct device *dev, int offset, int size)
 
 static int cros_flash_emul_get_protect(const struct device *dev, int bank)
 {
-	__ASSERT(false, "Not implemented");
-	return -EINVAL;
+	if (all_protected) {
+		return EC_ERROR_ACCESS_DENIED;
+	}
+	if (ro_protected && bank >= WP_BANK_OFFSET &&
+	    bank < WP_BANK_OFFSET + WP_BANK_COUNT) {
+		return EC_ERROR_ACCESS_DENIED;
+	}
+
+	return EC_SUCCESS;
 }
 
 static uint32_t cros_flash_emul_get_protect_flags(const struct device *dev)
 {
-	return EC_FLASH_PROTECT_ERROR_UNKNOWN;
+	uint32_t flags = 0;
+
+	if (ro_protected) {
+		flags |= EC_FLASH_PROTECT_RO_AT_BOOT | EC_FLASH_PROTECT_RO_NOW;
+	}
+	if (all_protected) {
+		flags |= EC_FLASH_PROTECT_ALL_NOW;
+	}
+	return flags;
 }
 
 static int cros_flash_emul_protect_at_boot(const struct device *dev,
 					   uint32_t new_flags)
 {
-	__ASSERT(false, "Not implemented");
-	return -EINVAL;
+	if ((new_flags & (EC_FLASH_PROTECT_RO_AT_BOOT |
+			  EC_FLASH_PROTECT_ALL_AT_BOOT)) == 0) {
+		/* Clear protection if allowed */
+		if (crec_flash_get_protect() & EC_FLASH_PROTECT_GPIO_ASSERTED) {
+			return EC_ERROR_ACCESS_DENIED;
+		}
+
+		ro_protected = all_protected = false;
+		return EC_SUCCESS;
+	}
+
+	ro_protected = true;
+
+	if (new_flags & EC_FLASH_PROTECT_ALL_AT_BOOT) {
+		all_protected = true;
+	}
+
+	return EC_SUCCESS;
 }
 
 static int cros_flash_emul_protect_now(const struct device *dev, int all)
 {
-	__ASSERT(false, "Not implemented");
-	return -EINVAL;
+	/* Emulate ALL_NOW only */
+	if (all) {
+		all_protected = true;
+	}
+
+	return EC_SUCCESS;
+}
+
+void cros_flash_emul_protect_reset(void)
+{
+	ro_protected = all_protected = false;
 }
 
 static int cros_flash_emul_get_jedec_id(const struct device *dev,
diff --git a/zephyr/include/emul/emul_flash.h b/zephyr/include/emul/emul_flash.h
new file mode 100644
index 0000000000..7316a8496d
--- /dev/null
+++ b/zephyr/include/emul/emul_flash.h
@@ -0,0 +1,20 @@
+/* Copyright 2022 The ChromiumOS Authors.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/**
+ * @file
+ *
+ * @brief Backend API for Cros flash emulator
+ */
+
+#ifndef ZEPHYR_INCLUDE_EMUL_EMUL_FLASH_H_
+#define ZEPHYR_INCLUDE_EMUL_EMUL_FLASH_H_
+
+/**
+ * @brief Reset the protection.
+ */
+void cros_flash_emul_protect_reset(void);
+
+#endif /* ZEPHYR_INCLUDE_EMUL_EMUL_FLASH_H_ */