lib: utils: Add cache flush library

The current RISC-V CMO only defines how to flush a cache block. However,
certain use cases, such as power management, may require flushing the
entire cache. Therefore, a framework is being introduced to allow vendors
to flush the entire cache using their own methods.

Signed-off-by: Nick Hu <nick.hu@sifive.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251020-cache-upstream-v7-1-69a132447d8a@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>

lib/utils/Kconfig

@@ -2,6 +2,8 @@
 
 menu "Utils and Drivers Support"
 
+source "$(OPENSBI_SRC_DIR)/lib/utils/cache/Kconfig"
+
 source "$(OPENSBI_SRC_DIR)/lib/utils/cppc/Kconfig"
 
 source "$(OPENSBI_SRC_DIR)/lib/utils/fdt/Kconfig"

lib/utils/cache/Kconfig

@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: BSD-2-Clause
+
+menu "Cache Support"
+
+config CACHE
+	bool "Cache support"
+	default n
+
+endmenu

lib/utils/cache/cache.c

@@ -0,0 +1,46 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 SiFive Inc.
+ */
+
+#include <sbi/sbi_error.h>
+#include <sbi_utils/cache/cache.h>
+
+static SBI_LIST_HEAD(cache_list);
+
+struct cache_device *cache_find(u32 id)
+{
+	struct cache_device *dev;
+
+	sbi_list_for_each_entry(dev, &cache_list, node) {
+		if (dev->id == id)
+			return dev;
+	}
+
+	return NULL;
+}
+
+int cache_add(struct cache_device *dev)
+{
+	if (!dev)
+		return SBI_ENODEV;
+
+	if (cache_find(dev->id))
+		return SBI_EALREADY;
+
+	sbi_list_add(&dev->node, &cache_list);
+
+	return SBI_OK;
+}
+
+int cache_flush_all(struct cache_device *dev)
+{
+	if (!dev)
+		return SBI_ENODEV;
+
+	if (!dev->ops || !dev->ops->cache_flush_all)
+		return SBI_ENOTSUPP;
+
+	return dev->ops->cache_flush_all(dev);
+}

lib/utils/cache/objects.mk

@@ -0,0 +1,7 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2025 SiFive
+#
+
+libsbiutils-objs-$(CONFIG_CACHE) += cache/cache.o