[loong64] Add CPU sleeping API for EFI LoongArch64

Signed-off-by: Xiaotian Wu <wuxiaotian@loongson.cn>
Modified-by: Michael Brown <mcb30@ipxe.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/loong64/Makefile

@@ -20,6 +20,7 @@ CFLAGS		+= -fshort-wchar
 
 # LoongArch64-specific directories containing source files
 SRCDIRS		+= arch/loong64/core
+SRCDIRS		+= arch/loong64/interface/efi
 
 # Include platform-specific Makefile
 MAKEDEPS	+= arch/loong64/Makefile.$(PLATFORM)

src/arch/loong64/include/bits/nap.h

@@ -9,4 +9,6 @@
 
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
-#endif /* _BITS_MAP_H */
+#include <ipxe/efi/efiloong64_nap.h>
+
+#endif /* _BITS_NAP_H */

src/arch/loong64/include/ipxe/efi/efiloong64_nap.h

@@ -0,0 +1,18 @@
+#ifndef _IPXE_EFILOONG64_NAP_H
+#define _IPXE_EFILOONG64_NAP_H
+
+/** @file
+ *
+ * EFI CPU sleeping
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#ifdef NAP_EFILOONG64
+#define NAP_PREFIX_efiloong64
+#else
+#define NAP_PREFIX_efiloong64 __efiloong64_
+#endif
+
+#endif /* _IPXE_EFILOONG64_NAP_H */

src/arch/loong64/interface/efi/efiloong64_nap.c

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2023, Xiaotian Wu <wuxiaotian@loongson.cn>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <ipxe/nap.h>
+#include <ipxe/efi/efi.h>
+
+/** @file
+ *
+ * iPXE CPU sleeping API for EFI
+ *
+ */
+
+/**
+ * Sleep until next interrupt
+ *
+ */
+static void efiloong64_cpu_nap ( void ) {
+	/*
+	 * I can't find any EFI API that allows us to put the CPU to
+	 * sleep.  The CpuSleep() function is defined in CpuLib.h, but
+	 * isn't part of any exposed protocol so we have no way to
+	 * call it.
+	 *
+	 * The EFI shell doesn't seem to bother sleeping the CPU; it
+	 * just sits there idly burning power.
+	 *
+	 */
+	__asm__ __volatile__ ( "idle 0" );
+}
+
+PROVIDE_NAP ( efiloong64, cpu_nap, efiloong64_cpu_nap );