[PATCH 1/5] lib: utils/cache: Add cache flush library

[Nick Hu]

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 at sifive.com>
Reviewed-by: Samuel Holland <samuel.holland at sifive.com>
---
 include/sbi_utils/cache/cache.h | 69 +++++++++++++++++++++++++++++++++
 lib/utils/Kconfig               |  2 +
 lib/utils/cache/Kconfig         |  9 +++++
 lib/utils/cache/cache.c         | 46 ++++++++++++++++++++++
 lib/utils/cache/objects.mk      |  7 ++++
 5 files changed, 133 insertions(+)
 create mode 100644 include/sbi_utils/cache/cache.h
 create mode 100644 lib/utils/cache/Kconfig
 create mode 100644 lib/utils/cache/cache.c
 create mode 100644 lib/utils/cache/objects.mk

diff --git a/include/sbi_utils/cache/cache.h b/include/sbi_utils/cache/cache.h
new file mode 100644
index 00000000..70d9286f
--- /dev/null
+++ b/include/sbi_utils/cache/cache.h
@@ -0,0 +1,69 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 SiFive Inc.
+ */
+
+#ifndef __CACHE_H__
+#define __CACHE_H__
+
+#include <sbi/sbi_list.h>
+#include <sbi/sbi_types.h>
+
+#define CACHE_NAME_LEN	32
+
+struct cache_device;
+
+struct cache_ops {
+	/** Warm init **/
+	int (*warm_init)(struct cache_device *dev);
+	/** Flush entire cache **/
+	int (*cache_flush_all)(struct cache_device *dev);
+};
+
+struct cache_device {
+	/** Name of the device **/
+	char name[CACHE_NAME_LEN];
+	/** List node for search **/
+	struct sbi_dlist node;
+	/** Point to the next level cache **/
+	struct cache_device *next;
+	/** Cache Management Operations **/
+	struct cache_ops *ops;
+	/** CPU private cache **/
+	bool cpu_private;
+	/** The unique id of this cache device **/
+	u32 id;
+};
+
+/**
+ * Find a registered cache device
+ *
+ * @param id unique ID of the cache device
+ *
+ * @return the cache device or NULL
+ */
+struct cache_device *cache_find(u32 id);
+
+/**
+ * Register a cache device
+ *
+ * cache_device->id must be initialized already and must not change during the life
+ * of the cache_device object.
+ *
+ * @param dev the cache device to register
+ *
+ * @return 0 on success, or a negative error code on failure
+ */
+int cache_add(struct cache_device *dev);
+
+/**
+ * Flush the entire cache
+ *
+ * @param dev the cache to flush
+ *
+ * @return 0 on success, or a negative error code on failure
+ */
+int cache_flush_all(struct cache_device *dev);
+
+#endif
diff --git a/lib/utils/Kconfig b/lib/utils/Kconfig
index 901ba564..5a5b3b1e 100644
--- a/lib/utils/Kconfig
+++ b/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 "$(OPENSBI_SRC_DIR)/lib/utils/fdt/Kconfig"
diff --git a/lib/utils/cache/Kconfig b/lib/utils/cache/Kconfig
new file mode 100644
index 00000000..24aa41bc
--- /dev/null
+++ b/lib/utils/cache/Kconfig
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: BSD-2-Clause
+
+menu "Cache Support"
+
+config CACHE
+	bool "Cache support"
+	default n
+
+endmenu
diff --git a/lib/utils/cache/cache.c b/lib/utils/cache/cache.c
new file mode 100644
index 00000000..6bc3d10e
--- /dev/null
+++ b/lib/utils/cache/cache.c
@@ -0,0 +1,46 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 SiFive Inc.
+ */
+
+#include <sbi/sbi_error.h>
+#include <sbi_utils/cache/cache.h>
+
+static SBI_LIST_HEAD(cache_list);
+
+struct cache_device *cache_find(u32 id)
+{
+	struct cache_device *dev;
+
+	sbi_list_for_each_entry(dev, &cache_list, node) {
+		if (dev->id == id)
+			return dev;
+	}
+
+	return NULL;
+}
+
+int cache_add(struct cache_device *dev)
+{
+	if (!dev)
+		return SBI_ENODEV;
+
+	if (cache_find(dev->id))
+		return SBI_EALREADY;
+
+	sbi_list_add(&dev->node, &cache_list);
+
+	return SBI_OK;
+}
+
+int cache_flush_all(struct cache_device *dev)
+{
+	if (!dev)
+		return SBI_ENODEV;
+
+	if (!dev->ops || !dev->ops->cache_flush_all)
+		return SBI_ENOTSUPP;
+
+	return dev->ops->cache_flush_all(dev);
+}
diff --git a/lib/utils/cache/objects.mk b/lib/utils/cache/objects.mk
new file mode 100644
index 00000000..21d30ce8
--- /dev/null
+++ b/lib/utils/cache/objects.mk
@@ -0,0 +1,7 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2025 SiFive
+#
+
+libsbiutils-objs-$(CONFIG_CACHE) += cache/cache.o
-- 
2.17.1