arm64: Move the LSE gas support detection to Kconfig

As the Kconfig syntax gained support for $(as-instr) tests, move the LSE
gas support detection from Makefile to the main arm64 Kconfig and remove
the additional CONFIG_AS_LSE definition and check.

Cc: Will Deacon <will@kernel.org>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/Kconfig

@@ -1363,6 +1363,11 @@ config ARM64_PAN
 	 instruction if the cpu does not implement the feature.
 
 config ARM64_LSE_ATOMICS
+	bool
+	default ARM64_USE_LSE_ATOMICS
+	depends on $(as-instr,.arch_extension lse)
+
+config ARM64_USE_LSE_ATOMICS
 	bool "Atomic instructions"
 	depends on JUMP_LABEL
 	default y

arch/arm64/Makefile

@@ -30,11 +30,8 @@ LDFLAGS_vmlinux	+= --fix-cortex-a53-843419
   endif
 endif
 
-# Check for binutils support for specific extensions
-lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)
-
-ifeq ($(CONFIG_ARM64_LSE_ATOMICS), y)
-  ifeq ($(lseinstr),)
+ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS), y)
+  ifneq ($(CONFIG_ARM64_LSE_ATOMICS), y)
 $(warning LSE atomics not supported by binutils)
   endif
 endif
@@ -53,11 +50,11 @@ $(warning Detected assembler with broken .inst; disassembly will be unreliable)
   endif
 endif
 
-KBUILD_CFLAGS	+= -mgeneral-regs-only $(lseinstr) $(brokengasinst)	\
+KBUILD_CFLAGS	+= -mgeneral-regs-only $(brokengasinst)	\
 		   $(compat_vdso) $(cc_has_k_constraint)
 KBUILD_CFLAGS	+= -fno-asynchronous-unwind-tables
 KBUILD_CFLAGS	+= $(call cc-disable-warning, psabi)
-KBUILD_AFLAGS	+= $(lseinstr) $(brokengasinst) $(compat_vdso)
+KBUILD_AFLAGS	+= $(brokengasinst) $(compat_vdso)
 
 KBUILD_CFLAGS	+= $(call cc-option,-mabi=lp64)
 KBUILD_AFLAGS	+= $(call cc-option,-mabi=lp64)

arch/arm64/include/asm/atomic_ll_sc.h

@@ -12,7 +12,7 @@
 
 #include <linux/stringify.h>
 
-#if IS_ENABLED(CONFIG_ARM64_LSE_ATOMICS) && IS_ENABLED(CONFIG_AS_LSE)
+#ifdef CONFIG_ARM64_LSE_ATOMICS
 #define __LL_SC_FALLBACK(asm_ops)					\
 "	b	3f\n"							\
 "	.subsection	1\n"						\

arch/arm64/include/asm/lse.h

@@ -4,7 +4,7 @@
 
 #include <asm/atomic_ll_sc.h>
 
-#if defined(CONFIG_AS_LSE) && defined(CONFIG_ARM64_LSE_ATOMICS)
+#ifdef CONFIG_ARM64_LSE_ATOMICS
 
 #include <linux/compiler_types.h>
 #include <linux/export.h>
@@ -36,7 +36,7 @@ static inline bool system_uses_lse_atomics(void)
 #define ARM64_LSE_ATOMIC_INSN(llsc, lse)				\
 	ALTERNATIVE(llsc, lse, ARM64_HAS_LSE_ATOMICS)
 
-#else	/* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
+#else	/* CONFIG_ARM64_LSE_ATOMICS */
 
 static inline bool system_uses_lse_atomics(void) { return false; }
 
@@ -44,5 +44,5 @@ static inline bool system_uses_lse_atomics(void) { return false; }
 
 #define ARM64_LSE_ATOMIC_INSN(llsc, lse)	llsc
 
-#endif	/* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
+#endif	/* CONFIG_ARM64_LSE_ATOMICS */
 #endif	/* __ASM_LSE_H */

arch/arm64/kernel/cpufeature.c

@@ -1291,7 +1291,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.cpu_enable = cpu_enable_pan,
 	},
 #endif /* CONFIG_ARM64_PAN */
-#if defined(CONFIG_AS_LSE) && defined(CONFIG_ARM64_LSE_ATOMICS)
+#ifdef CONFIG_ARM64_LSE_ATOMICS
 	{
 		.desc = "LSE atomic instructions",
 		.capability = ARM64_HAS_LSE_ATOMICS,
@@ -1302,7 +1302,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.sign = FTR_UNSIGNED,
 		.min_field_value = 2,
 	},
-#endif /* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
+#endif /* CONFIG_ARM64_LSE_ATOMICS */
 	{
 		.desc = "Software prefetching using PRFM",
 		.capability = ARM64_HAS_NO_HW_PREFETCH,