[PATCH cmpxchg 3/3] sh: Emulate one-byte cmpxchg

[John Paul Adrian Glaubitz]

On Mon, 2024-08-05 at 12:21 -0700, Paul E. McKenney wrote:
> Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on sh.
> 
> [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]
> [ paulmck: Apply feedback from Naresh Kamboju. ]
> [ Apply Geert Uytterhoeven feedback. ]
> 
> Signed-off-by: Paul E. McKenney <paulmck at kernel.org>
> Cc: Andi Shyti <andi.shyti at linux.intel.com>
> Cc: Palmer Dabbelt <palmer at rivosinc.com>
> Cc: Masami Hiramatsu <mhiramat at kernel.org>
> Cc: Arnd Bergmann <arnd at arndb.de>
> Cc: <linux-sh at vger.kernel.org>
> ---
>  arch/sh/Kconfig               | 1 +
>  arch/sh/include/asm/cmpxchg.h | 3 +++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
> index 1aa3c4a0c5b27..e9103998cca91 100644
> --- a/arch/sh/Kconfig
> +++ b/arch/sh/Kconfig
> @@ -14,6 +14,7 @@ config SUPERH
>  	select ARCH_HIBERNATION_POSSIBLE if MMU
>  	select ARCH_MIGHT_HAVE_PC_PARPORT
>  	select ARCH_WANT_IPC_PARSE_VERSION
> +	select ARCH_NEED_CMPXCHG_1_EMU
>  	select CPU_NO_EFFICIENT_FFS
>  	select DMA_DECLARE_COHERENT
>  	select GENERIC_ATOMIC64
> diff --git a/arch/sh/include/asm/cmpxchg.h b/arch/sh/include/asm/cmpxchg.h
> index 5d617b3ef78f7..1e5dc5ccf7bf5 100644
> --- a/arch/sh/include/asm/cmpxchg.h
> +++ b/arch/sh/include/asm/cmpxchg.h
> @@ -9,6 +9,7 @@
>  
>  #include <linux/compiler.h>
>  #include <linux/types.h>
> +#include <linux/cmpxchg-emu.h>
>  
>  #if defined(CONFIG_GUSA_RB)
>  #include <asm/cmpxchg-grb.h>
> @@ -56,6 +57,8 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old,
>  		unsigned long new, int size)
>  {
>  	switch (size) {
> +	case 1:
> +		return cmpxchg_emu_u8(ptr, old, new);
>  	case 4:
>  		return __cmpxchg_u32(ptr, old, new);
>  	}

Acked-by: John Paul Adrian Glaubitz <glaubitz at physik.fu-berlin.de>

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913