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riscv: Provide a definition for 'pause'

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If we're going to provide the encoding for 'pause' in cpu_relax()
anyway, then we can drop the toolchain checks and just always use
it. The advantage of doing this is that other code that need
pause don't need to also define it (yes, another use is coming).
Add the definition to insn-def.h since it's an instruction
definition and also because insn-def.h doesn't include much, so
it's safe to include from asm/vdso/processor.h without concern for
circular dependencies.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20240426100820.14762-9-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Andrew Jones 2024-04-26 12:08:21 +02:00 committed by Palmer Dabbelt
parent 4cece76496
commit 6da111574b
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4 changed files with 4 additions and 16 deletions
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7
arch/riscv/Kconfig
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@ -639,13 +639,6 @@ config RISCV_ISA_ZICBOZ
If you don't know what to do here, say Y.
config TOOLCHAIN_HAS_ZIHINTPAUSE
bool
default y
depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zihintpause)
depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zihintpause)
depends on LLD_VERSION >= 150000 || LD_VERSION >= 23600
config TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI
def_bool y
# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc

3
arch/riscv/Makefile
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@ -75,9 +75,6 @@ else
riscv-march-$(CONFIG_TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI) := $(riscv-march-y)_zicsr_zifencei
endif
# Check if the toolchain supports Zihintpause extension
riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE) := $(riscv-march-y)_zihintpause
# Remove F,D,V from isa string for all. Keep extensions between "fd" and "v" by
# matching non-v and non-multi-letter extensions out with the filter ([^v_]*)
KBUILD_CFLAGS += -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)fd([^v_]*)v?/\1\2/')

2
arch/riscv/include/asm/insn-def.h
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@ -196,4 +196,6 @@
INSN_I(OPCODE_MISC_MEM, FUNC3(2), __RD(0), \
RS1(base), SIMM12(4))
#define RISCV_PAUSE ".4byte 0x100000f"
#endif /* __ASM_INSN_DEF_H */

8
arch/riscv/include/asm/vdso/processor.h
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@ -5,6 +5,7 @@
#ifndef __ASSEMBLY__
#include <asm/barrier.h>
#include <asm/insn-def.h>
static inline void cpu_relax(void)
{
@ -14,16 +15,11 @@ static inline void cpu_relax(void)
__asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
#endif
#ifdef CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE
/*
* Reduce instruction retirement.
* This assumes the PC changes.
*/
__asm__ __volatile__ ("pause");
#else
/* Encoding of the pause instruction */
__asm__ __volatile__ (".4byte 0x100000F");
#endif
__asm__ __volatile__ (RISCV_PAUSE);
barrier();
}