lib: sbi: Implement SBI CPPC extension

Implement SBI CPPC extension. This extension is only available when
OpenSBI platform provides a CPPC device to generic library.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

include/sbi/sbi_cppc.h

@@ -0,0 +1,35 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2023 Ventana Micro Systems Inc.
+ *
+ */
+
+#ifndef __SBI_CPPC_H__
+#define __SBI_CPPC_H__
+
+#include <sbi/sbi_types.h>
+
+/** CPPC device */
+struct sbi_cppc_device {
+	/** Name of the CPPC device */
+	char name[32];
+
+	/** probe - returns register width if implemented, 0 otherwise */
+	int (*cppc_probe)(unsigned long reg);
+
+	/** read the cppc register*/
+	int (*cppc_read)(unsigned long reg, uint64_t *val);
+
+	/** write to the cppc register*/
+	int (*cppc_write)(unsigned long reg, uint64_t val);
+};
+
+int sbi_cppc_probe(unsigned long reg);
+int sbi_cppc_read(unsigned long reg, uint64_t *val);
+int sbi_cppc_write(unsigned long reg, uint64_t val);
+
+const struct sbi_cppc_device *sbi_cppc_get_device(void);
+void sbi_cppc_set_device(const struct sbi_cppc_device *dev);
+
+#endif