loongarch64: new target

Add target for Loongson LoongArch64-based boards.

LoongArch is a new RISC ISA developed by Loongson. It's a bit like
MIPS or RISC-V. LoongArch includes both 32-bit and 64-bit versions
(LoongArch32/LoongArch64).

Loongson 3A5000 and 3A6000 are the two existing CPUs of LoongArch64
and is used for PC products. It's BIOS supports ACPI and UEFI-only
boot. These CPUs supports SMP and SMT.

At present only LoongArch64 is supported by linux kernel.

Toolchain requirement:
binutils >= 2.40
gcc >= 13.1

For details, please check the following links:
https://lwn.net/Articles/861951/
https://loongson.github.io/LoongArch-Documentation/README-EN.html

Signed-off-by: Weijie Gao <hackpascal@gmail.com>

include/kernel.mk

@@ -86,6 +86,8 @@ else ifneq (,$(findstring $(ARCH) , arceb ))
   LINUX_KARCH := arc
 else ifneq (,$(findstring $(ARCH) , armeb ))
   LINUX_KARCH := arm
+else ifneq (,$(findstring $(ARCH) , loongarch64 ))
+  LINUX_KARCH := loongarch
 else ifneq (,$(findstring $(ARCH) , mipsel mips64 mips64el ))
   LINUX_KARCH := mips
 else ifneq (,$(findstring $(ARCH) , powerpc64 ))

include/site/loongarch64

@@ -0,0 +1,30 @@
+#!/bin/sh
+. $TOPDIR/include/site/linux
+ac_cv_c_littleendian=${ac_cv_c_littleendian=yes}
+ac_cv_c_bigendian=${ac_cv_c_bigendian=no}
+
+ac_cv_sizeof___int64=0
+ac_cv_sizeof_char=1
+ac_cv_sizeof_int=4
+ac_cv_sizeof_int16_t=2
+ac_cv_sizeof_int32_t=4
+ac_cv_sizeof_int64_t=8
+ac_cv_sizeof_long_int=8
+ac_cv_sizeof_long_long=8
+ac_cv_sizeof_long=8
+ac_cv_sizeof_off_t=8
+ac_cv_sizeof_short_int=2
+ac_cv_sizeof_short=2
+ac_cv_sizeof_size_t=8
+ac_cv_sizeof_ssize_t=8
+ac_cv_sizeof_u_int16_t=2
+ac_cv_sizeof_u_int32_t=4
+ac_cv_sizeof_u_int64_t=8
+ac_cv_sizeof_uint16_t=2
+ac_cv_sizeof_uint32_t=4
+ac_cv_sizeof_uint64_t=8
+ac_cv_sizeof_unsigned_int=4
+ac_cv_sizeof_unsigned_long=8
+ac_cv_sizeof_unsigned_long_long=8
+ac_cv_sizeof_unsigned_short=2
+ac_cv_sizeof_void_p=8

include/target.mk

@@ -264,6 +264,11 @@ ifeq ($(DUMP),1)
     CPU_TYPE ?= riscv64
     CPU_CFLAGS_riscv64:=-mabi=lp64d -march=rv64imafdc
   endif
+  ifeq ($(ARCH),loongarch64)
+    CPU_TYPE ?= generic
+    CPU_CFLAGS := -O2 -pipe
+    CPU_CFLAGS_generic:=-march=loongarch64
+  endif
   ifneq ($(CPU_TYPE),)
     ifndef CPU_CFLAGS_$(CPU_TYPE)
       $(warning CPU_TYPE "$(CPU_TYPE)" doesn't correspond to a known type)