[PATCH] RISC-V: Avoid coupling the T-Head CMOs and Zicbom

[Conor.Dooley at microchip.com]

On 15/09/2022 18:09, Palmer Dabbelt wrote:
> We could make the T-Head CMOs depend on a new-enough assembler to have
> Zicbom, but it's not strictly necessary because the T-Head CMOs
> circumvent the assembler.
> 
> Fixes: 8f7e001e0325 ("RISC-V: Clean up the Zicbom block size probing")
> Cc: stable at vger.kernel.org
> Reported-by: kernel test robot <lkp at intel.com>
> Reported-by: Conor Dooley <conor.dooley at microchip.com>

I build-tested this last night when I accidentally found it so:
Reviewed-by: Conor Dooley <conor.dooley at microchip.com>

> Signed-off-by: Palmer Dabbelt <palmer at rivosinc.com>
> ---
>  arch/riscv/include/asm/cacheflush.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
> index a89c005b4bbf..273ece6b622f 100644
> --- a/arch/riscv/include/asm/cacheflush.h
> +++ b/arch/riscv/include/asm/cacheflush.h
> @@ -42,8 +42,12 @@ void flush_icache_mm(struct mm_struct *mm, bool local);
>  
>  #endif /* CONFIG_SMP */
>  
> -#ifdef CONFIG_RISCV_ISA_ZICBOM
> +/*
> + * The T-Head CMO errata internally probe the CBOM block size, but otherwise
> + * don't depend on Zicbom.
> + */
>  extern unsigned int riscv_cbom_block_size;
> +#ifdef CONFIG_RISCV_ISA_ZICBOM
>  void riscv_init_cbom_blocksize(void);
>  #else
>  static inline void riscv_init_cbom_blocksize(void) { }