arm_fpga: Add support for unknown MPIDs

This patch allows the system to fallback to a default CPU library
in case the MPID does not match with any of the supported ones.

This feature can be enabled by setting SUPPORT_UNKNOWN_MPID build
option to 1 (enabled by default only on arm_fpga platform).

This feature can be very dangerous on a production image and
therefore it MUST be disabled for Release images.

Signed-off-by: Javier Almansa Sobrino <javier.almansasobrino@arm.com>
Change-Id: I0df7ef2b012d7d60a4fd5de44dea1fbbb46881ba
diff --git a/lib/cpus/aarch64/generic.S b/lib/cpus/aarch64/generic.S
new file mode 100644
index 0000000..ef1f048
--- /dev/null
+++ b/lib/cpus/aarch64/generic.S
@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2020, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch.h>
+#include <asm_macros.S>
+#include <common/bl_common.h>
+#include <generic.h>
+#include <cpu_macros.S>
+#include <plat_macros.S>
+
+	/* ---------------------------------------------
+	 * Disable L1 data cache and unified L2 cache
+	 * ---------------------------------------------
+	 */
+func generic_disable_dcache
+	mrs	x1, sctlr_el3
+	bic	x1, x1, #SCTLR_C_BIT
+	msr	sctlr_el3, x1
+	isb
+	ret
+endfunc generic_disable_dcache
+
+func generic_core_pwr_dwn
+	mov	x18, x30
+
+	/* ---------------------------------------------
+	 * Turn off caches.
+	 * ---------------------------------------------
+	 */
+	bl	generic_disable_dcache
+
+	/* ---------------------------------------------
+	 * Flush L1 caches.
+	 * ---------------------------------------------
+	 */
+	mov	x0, #DCCISW
+	bl	dcsw_op_level1
+
+	ret	x18
+endfunc generic_core_pwr_dwn
+
+func generic_cluster_pwr_dwn
+	mov	x18, x30
+
+	/* ---------------------------------------------
+	 * Turn off caches.
+	 * ---------------------------------------------
+	 */
+	bl	generic_disable_dcache
+
+	/* ---------------------------------------------
+	 * Flush L1 caches.
+	 * ---------------------------------------------
+	 */
+	mov	x0, #DCCISW
+	bl	dcsw_op_level1
+
+	/* ---------------------------------------------
+	 * Disable the optional ACP.
+	 * ---------------------------------------------
+	 */
+	bl	plat_disable_acp
+
+	/* ---------------------------------------------
+	 * Flush L2 caches.
+	 * ---------------------------------------------
+	 */
+	mov	x0, #DCCISW
+	bl	dcsw_op_level2
+
+	ret	x18
+
+endfunc generic_cluster_pwr_dwn
+
+/* ---------------------------------------------
+ * Unimplemented functions.
+ * ---------------------------------------------
+ */
+.equ	generic_errata_report,		0
+.equ	generic_cpu_reg_dump,		0
+.equ	generic_reset_func,		0
+
+declare_cpu_ops generic, AARCH64_GENERIC_MIDR, \
+	generic_reset_func, \
+	generic_core_pwr_dwn, \
+	generic_cluster_pwr_dwn