[PATCH v2 2/2] arm64: Move the LSE gas support detection to Kconfig

Catalin Marinas
2020-01-15T11:30:49Z

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>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

Notes:
v2:
- Re-introduce build-time warning if .config wants LSE atomics but gas
does not support it
- Given that the patch was modified, I have not added Vladimir's
reviewed-by tag on v1

arch/arm64/Kconfig | 5 +++++
arch/arm64/Makefile | 11 ++++-------
arch/arm64/include/asm/atomic_ll_sc.h | 2 +-
arch/arm64/include/asm/lse.h | 6 +++---
arch/arm64/kernel/cpufeature.c | 4 ++--
5 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b1b4476ddb83..cf3b6d2a67cf 100644
--- a/arch/arm64/Kconfig
+++ b/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
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 1fbe24d4fdb6..6dd8ecacc428 100644
--- a/arch/arm64/Makefile
+++ b/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)
diff --git a/arch/arm64/include/asm/atomic_ll_sc.h b/arch/arm64/include/asm/atomic_ll_sc.h
index 7b012148bfd6..13869b76b58c 100644
--- a/arch/arm64/include/asm/atomic_ll_sc.h
+++ b/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" \
diff --git a/arch/arm64/include/asm/lse.h b/arch/arm64/include/asm/lse.h
index 80b388278149..4e1009fff686 100644
--- a/arch/arm64/include/asm/lse.h
+++ b/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 */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 04cf64e9f0c9..2595c2886d3f 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/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,