[PATCH v6 7/8] powerpc/pmem: Add WARN_ONCE to catch the wrong usage of pmem flush functions.

[Dan Williams]

On Mon, Jun 29, 2020 at 6:58 AM Aneesh Kumar K.V
<aneesh.kumar at linux.ibm.com> wrote:
>
> We only support persistent memory on P8 and above. This is enforced by the
> firmware and further checked on virtualzied platform during platform init.
> Add WARN_ONCE in pmem flush routines to catch the wrong usage of these.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
> ---
>  arch/powerpc/include/asm/cacheflush.h | 2 ++
>  arch/powerpc/lib/pmem.c               | 2 ++
>  2 files changed, 4 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/cacheflush.h b/arch/powerpc/include/asm/cacheflush.h
> index 95782f77d768..1ab0fa660497 100644
> --- a/arch/powerpc/include/asm/cacheflush.h
> +++ b/arch/powerpc/include/asm/cacheflush.h
> @@ -103,6 +103,8 @@ static inline void  arch_pmem_flush_barrier(void)
>  {
>         if (cpu_has_feature(CPU_FTR_ARCH_207S))
>                 asm volatile(PPC_PHWSYNC ::: "memory");
> +       else
> +               WARN_ONCE(1, "Using pmem flush on older hardware.");

This seems too late to be making this determination. I'd expect the
driver to fail to successfully bind default if this constraint is not
met.