On Tue, May 19, 2015 at 07:33:33PM +0100, Peter Maydell wrote:
> Just NOP the WFI instruction if we have work to do.
> This doesn't make much difference currently (though it does avoid
> jumping out to the top level loop and immediately restarting),
> but the distinction between "halt" and "don't halt" will become
> more important when the decision to halt requires us to trap
> to a higher exception level instead.
>
> Suggested-by: Edgar E. Iglesias <edgar.igles...@xilinx.com>
> Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.igles...@xilinx.com>
> ---
> target-arm/op_helper.c | 7 +++++++
> target-arm/translate-a64.c | 4 ++++
> target-arm/translate.c | 4 ++++
> 3 files changed, 15 insertions(+)
>
> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
> index 5963f3b..517dacc 100644
> --- a/target-arm/op_helper.c
> +++ b/target-arm/op_helper.c
> @@ -252,6 +252,13 @@ void HELPER(wfi)(CPUARMState *env)
> {
> CPUState *cs = CPU(arm_env_get_cpu(env));
>
> + if (cpu_has_work(cs)) {
> + /* Don't bother to go into our "low power state" if
> + * we would just wake up immediately.
> + */
> + return;
> + }
> +
> cs->exception_index = EXCP_HLT;
> cs->halted = 1;
> cpu_loop_exit(cs);
> diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
> index 8d08ccd..ffa6cb8 100644
> --- a/target-arm/translate-a64.c
> +++ b/target-arm/translate-a64.c
> @@ -11113,6 +11113,10 @@ void gen_intermediate_code_internal_a64(ARMCPU *cpu,
> */
> gen_a64_set_pc_im(dc->pc);
> gen_helper_wfi(cpu_env);
> + /* The helper doesn't necessarily throw an exception, but we
> + * must go back to the main loop to check for interrupts anyway.
> + */
> + tcg_gen_exit_tb(0);
> break;
> }
> }
> diff --git a/target-arm/translate.c b/target-arm/translate.c
> index ed2c43d..6493b9a 100644
> --- a/target-arm/translate.c
> +++ b/target-arm/translate.c
> @@ -11351,6 +11351,10 @@ static inline void
> gen_intermediate_code_internal(ARMCPU *cpu,
> break;
> case DISAS_WFI:
> gen_helper_wfi(cpu_env);
> + /* The helper doesn't necessarily throw an exception, but we
> + * must go back to the main loop to check for interrupts anyway.
> + */
> + tcg_gen_exit_tb(0);
> break;
> case DISAS_WFE:
> gen_helper_wfe(cpu_env);
> --
> 1.9.1
>
