Re: [PATCH 09/18] soc: qcom: ipa: GSI transactions

[Arnd Bergmann]

On Sun, May 19, 2019 at 7:11 PM Alex Elder <elder@xxxxxxxxxx> wrote:
> On 5/17/19 1:44 PM, Alex Elder wrote:
> > On 5/17/19 1:33 PM, Arnd Bergmann wrote:
> >> On Fri, May 17, 2019 at 8:08 PM Alex Elder <elder@xxxxxxxxxx>
>
> So it seems that I must *not* apply a volatile qualifier,
> because doing so restricts the compiler from making the
> single instruction optimization.

Right, I guess that makes sense.

> If I've missed something and you have another suggestion for
> me to try let me know and I'll try it.

A memcpy() might do the right thing as well. Another idea would
be a cast to __int128 like

#ifdef CONFIG_ARCH_SUPPORTS_INT128
typedef __int128 tre128_t;
#else
typedef struct { __u64 a; __u64 b; } tre128_t;
#else

static inline void set_tre(struct gsi_tre *dest_tre, struct gs_tre *src_tre)
{
     *(volatile tre128_t *)dest_tre = *(tre128_t *)src_tre;
}

      Arnd