mips: sync asm/mipsregs.h with Linux 5.7

Sync asm/mipsregs.h with Linux 5.7. Also replace the custom
symbols EBASE_CPUNUM and EBASE_WG with the according symbols
from Linux.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>

arch/mips/cpu/start.S

@@ -138,7 +138,7 @@ reset:
 	and	t0, t0, (1 << 31)
 #else
 1:	mfc0	t0, CP0_EBASE
-	and	t0, t0, EBASE_CPUNUM
+	and	t0, t0, MIPS_EBASE_CPUNUM
 #endif
 
 	/* Hang if this isn't the first CPU in the system */

arch/mips/include/asm/compiler.h

@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2004, 2007  Maciej W. Rozycki
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#ifndef _ASM_COMPILER_H
+#define _ASM_COMPILER_H
+
+/*
+ * With GCC 4.5 onwards we can use __builtin_unreachable to indicate to the
+ * compiler that a particular code path will never be hit. This allows it to be
+ * optimised out of the generated binary.
+ *
+ * Unfortunately at least GCC 4.6.3 through 7.3.0 inclusive suffer from a bug
+ * that can lead to instructions from beyond an unreachable statement being
+ * incorrectly reordered into earlier delay slots if the unreachable statement
+ * is the only content of a case in a switch statement. This can lead to
+ * seemingly random behaviour, such as invalid memory accesses from incorrectly
+ * reordered loads or stores. See this potential GCC fix for details:
+ *
+ *   https://gcc.gnu.org/ml/gcc-patches/2015-09/msg00360.html
+ *
+ * It is unclear whether GCC 8 onwards suffer from the same issue - nothing
+ * relevant is mentioned in GCC 8 release notes and nothing obviously relevant
+ * stands out in GCC commit logs, but these newer GCC versions generate very
+ * different code for the testcase which doesn't exhibit the bug.
+ *
+ * GCC also handles stack allocation suboptimally when calling noreturn
+ * functions or calling __builtin_unreachable():
+ *
+ *   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
+ *
+ * We work around both of these issues by placing a volatile asm statement,
+ * which GCC is prevented from reordering past, prior to __builtin_unreachable
+ * calls.
+ *
+ * The .insn statement is required to ensure that any branches to the
+ * statement, which sadly must be kept due to the asm statement, are known to
+ * be branches to code and satisfy linker requirements for microMIPS kernels.
+ */
+#undef barrier_before_unreachable
+#define barrier_before_unreachable() asm volatile(".insn")
+
+#if !defined(CONFIG_CC_IS_GCC) || \
+    (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+# define GCC_OFF_SMALL_ASM() "ZC"
+#elif defined(CONFIG_CPU_MICROMIPS)
+# error "microMIPS compilation unsupported with GCC older than 4.9"
+#else
+# define GCC_OFF_SMALL_ASM() "R"
+#endif
+
+#ifdef CONFIG_CPU_MIPSR6
+#define MIPS_ISA_LEVEL "mips64r6"
+#define MIPS_ISA_ARCH_LEVEL MIPS_ISA_LEVEL
+#define MIPS_ISA_LEVEL_RAW mips64r6
+#define MIPS_ISA_ARCH_LEVEL_RAW MIPS_ISA_LEVEL_RAW
+#else
+/* MIPS64 is a superset of MIPS32 */
+#define MIPS_ISA_LEVEL "mips64r2"
+#define MIPS_ISA_ARCH_LEVEL "arch=r4000"
+#define MIPS_ISA_LEVEL_RAW mips64r2
+#define MIPS_ISA_ARCH_LEVEL_RAW MIPS_ISA_LEVEL_RAW
+#endif /* CONFIG_CPU_MIPSR6 */
+
+#endif /* _ASM_COMPILER_H */

arch/mips/include/asm/isa-rev.h

@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2018 MIPS Tech, LLC
+ * Author: Matt Redfearn <matt.redfearn@mips.com>
+ */
+
+#ifndef __MIPS_ASM_ISA_REV_H__
+#define __MIPS_ASM_ISA_REV_H__
+
+/*
+ * The ISA revision level. This is 0 for MIPS I to V and N for
+ * MIPS{32,64}rN.
+ */
+
+/* If the compiler has defined __mips_isa_rev, believe it. */
+#ifdef __mips_isa_rev
+#define MIPS_ISA_REV __mips_isa_rev
+#else
+/* The compiler hasn't defined the isa rev so assume it's MIPS I - V (0) */
+#define MIPS_ISA_REV 0
+#endif
+
+
+#endif /* __MIPS_ASM_ISA_REV_H__ */

arch/mips/lib/traps.c

@@ -110,7 +110,7 @@ void trap_init(ulong reloc_addr)
 
 	/* Set WG bit on Octeon to enable writing to bits 63:30 */
 	if (IS_ENABLED(CONFIG_ARCH_OCTEON))
-		ebase |= EBASE_WG;
+		ebase |= MIPS_EBASE_WG;
 
 	write_c0_ebase(ebase);
 	clear_c0_status(ST0_BEV);