lib: utils: Add FDT cache library

Add the FDT cache library so we can build up the cache topology via the
'next-level-cache' DT property.

Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Co-developed-by: Andy Chiu <andy.chiu@sifive.com>
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
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-v7-2-69a132447d8a@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>

include/sbi_utils/cache/fdt_cache.h

@@ -0,0 +1,34 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 SiFive Inc.
+ */
+
+#ifndef __FDT_CACHE_H__
+#define __FDT_CACHE_H__
+
+#include <sbi_utils/cache/cache.h>
+
+/**
+ * Register a cache device using information from the DT
+ *
+ * @param fdt devicetree blob
+ * @param noff offset of a node in the devicetree blob
+ * @param dev cache device to register for this devicetree node
+ *
+ * @return 0 on success, or a negative error code on failure
+ */
+int fdt_cache_add(const void *fdt, int noff, struct cache_device *dev);
+
+/**
+ * Get the cache device referencd by the "next-level-cache" property of a DT node
+ *
+ * @param fdt devicetree blob
+ * @param noff offset of a node in the devicetree blob
+ * @param out_dev location to return the cache device
+ *
+ * @return 0 on success, or a negative error code on failure
+ */
+int fdt_next_cache_get(const void *fdt, int noff, struct cache_device **out_dev);
+
+#endif

lib/utils/cache/Kconfig

@@ -2,6 +2,12 @@
 
 menu "Cache Support"
 
+config FDT_CACHE
+	bool "FDT based cache drivers"
+	depends on FDT
+	select CACHE
+	default n
+
 config CACHE
 	bool "Cache support"
 	default n

lib/utils/cache/fdt_cache.c

@@ -0,0 +1,87 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 SiFive Inc.
+ */
+
+#include <libfdt.h>
+#include <sbi/sbi_console.h>
+#include <sbi/sbi_error.h>
+#include <sbi/sbi_heap.h>
+#include <sbi_utils/cache/fdt_cache.h>
+#include <sbi_utils/fdt/fdt_driver.h>
+
+/* List of FDT cache drivers generated at compile time */
+extern const struct fdt_driver *const fdt_cache_drivers[];
+
+int fdt_cache_add(const void *fdt, int noff, struct cache_device *dev)
+{
+	int rc;
+
+	dev->id = noff;
+	sbi_strncpy(dev->name, fdt_get_name(fdt, noff, NULL), sizeof(dev->name) - 1);
+	sbi_dprintf("%s: %s\n", __func__, dev->name);
+
+	rc = fdt_next_cache_get(fdt, noff, &dev->next);
+	if (rc)
+		return rc;
+
+	return cache_add(dev);
+}
+
+static int fdt_cache_add_generic(const void *fdt, int noff)
+{
+	struct cache_device *dev;
+	int rc;
+
+	dev = sbi_zalloc(sizeof(*dev));
+	if (!dev)
+		return SBI_ENOMEM;
+
+	rc = fdt_cache_add(fdt, noff, dev);
+	if (rc) {
+		sbi_free(dev);
+		return rc;
+	}
+
+	return 0;
+}
+
+static int fdt_cache_find(const void *fdt, int noff, struct cache_device **out_dev)
+{
+	struct cache_device *dev = cache_find(noff);
+	int rc;
+
+	if (!dev) {
+		rc = fdt_driver_init_by_offset(fdt, noff, fdt_cache_drivers);
+		if (rc == SBI_ENODEV)
+			rc = fdt_cache_add_generic(fdt, noff);
+		if (rc)
+			return rc;
+
+		dev = cache_find(noff);
+		if (!dev)
+			return SBI_EFAIL;
+	}
+
+	if (out_dev)
+		*out_dev = dev;
+
+	return SBI_OK;
+}
+
+int fdt_next_cache_get(const void *fdt, int noff, struct cache_device **out_dev)
+{
+	const fdt32_t *val;
+	int len;
+
+	val = fdt_getprop(fdt, noff, "next-level-cache", &len);
+	if (!val || len < sizeof(*val))
+		return SBI_ENOENT;
+
+	noff = fdt_node_offset_by_phandle(fdt, fdt32_to_cpu(val[0]));
+	if (noff < 0)
+		return noff;
+
+	return fdt_cache_find(fdt, noff, out_dev);
+}

lib/utils/cache/fdt_cache_drivers.carray

@@ -0,0 +1,3 @@
+HEADER: sbi_utils/cache/fdt_cache.h
+TYPE: const struct fdt_driver
+NAME: fdt_cache_drivers

lib/utils/cache/objects.mk

@@ -4,4 +4,7 @@
 # Copyright (c) 2025 SiFive
 #
 
+libsbiutils-objs-$(CONFIG_FDT_CACHE) += cache/fdt_cache.o
+libsbiutils-objs-$(CONFIG_FDT_CACHE) += cache/fdt_cache_drivers.carray.o
+
 libsbiutils-objs-$(CONFIG_CACHE) += cache/cache.o

platform/generic/configs/defconfig

@@ -10,6 +10,7 @@ CONFIG_PLATFORM_STARFIVE_JH7110=y
 CONFIG_PLATFORM_THEAD=y
 CONFIG_PLATFORM_MIPS_P8700=y
 CONFIG_PLATFORM_SPACEMIT_K1=y
+CONFIG_FDT_CACHE=y
 CONFIG_FDT_CPPC=y
 CONFIG_FDT_CPPC_RPMI=y
 CONFIG_FDT_GPIO=y