Re: [PATCH] target/ppc: Make HDECR underflow edge triggered

[Cédric Le Goater]

On 6/25/23 14:20, Nicholas Piggin wrote:
> HDEC interrupts are edge-triggered on HDECR underflow (notably different
> from DEC which is level-triggered).

yes.
 
> HDEC interrupts already clear the irq on delivery so that does not need
> to be changed.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Reviewed-by: Cédric Le Goater <clg@kaod.org>

Thanks,

C.

> ---
>   hw/ppc/ppc.c | 16 +++++++++-------
>   1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
> index 7b7db30f95..f4fe1767d6 100644
> --- a/hw/ppc/ppc.c
> +++ b/hw/ppc/ppc.c
> @@ -789,8 +789,8 @@ static void __cpu_ppc_store_decr(PowerPCCPU *cpu, uint64_t 
> *nextp,
>                                    QEMUTimer *timer,
>                                    void (*raise_excp)(void *),
>                                    void (*lower_excp)(PowerPCCPU *),
> -                                 target_ulong decr, target_ulong value,
> -                                 int nr_bits)
> +                                 uint32_t flags, target_ulong decr,
> +                                 target_ulong value, int nr_bits)
>   {
>       CPUPPCState *env = &cpu->env;
>       ppc_tb_t *tb_env = env->tb_env;
> @@ -820,15 +820,15 @@ static void __cpu_ppc_store_decr(PowerPCCPU *cpu, 
> uint64_t *nextp,
>        * On MSB edge based DEC implementations the MSB going from 0 -> 1 
> triggers
>        * an edge interrupt, so raise it here too.
>        */
> -    if (((tb_env->flags & PPC_DECR_UNDERFLOW_LEVEL) && signed_value < 0) ||
> -        ((tb_env->flags & PPC_DECR_UNDERFLOW_TRIGGERED) && signed_value < 0
> +    if (((flags & PPC_DECR_UNDERFLOW_LEVEL) && signed_value < 0) ||
> +        ((flags & PPC_DECR_UNDERFLOW_TRIGGERED) && signed_value < 0
>             && signed_decr >= 0)) {
>           (*raise_excp)(cpu);
>           return;
>       }
>   
>       /* On MSB level based systems a 0 for the MSB stops interrupt delivery */
> -    if (signed_value >= 0 && (tb_env->flags & PPC_DECR_UNDERFLOW_LEVEL)) {
> +    if (signed_value >= 0 && (flags & PPC_DECR_UNDERFLOW_LEVEL)) {
>           (*lower_excp)(cpu);
>       }
>   
> @@ -847,8 +847,8 @@ static inline void _cpu_ppc_store_decr(PowerPCCPU *cpu, target_ulong decr,
>       ppc_tb_t *tb_env = cpu->env.tb_env;
>   
>       __cpu_ppc_store_decr(cpu, &tb_env->decr_next, tb_env->decr_timer,
> -                         tb_env->decr_timer->cb, &cpu_ppc_decr_lower, decr,
> -                         value, nr_bits);
> +                         tb_env->decr_timer->cb, &cpu_ppc_decr_lower,
> +                         tb_env->flags, decr, value, nr_bits);
>   }
>   
>   void cpu_ppc_store_decr(CPUPPCState *env, target_ulong value)
> @@ -877,8 +877,10 @@ static inline void _cpu_ppc_store_hdecr(PowerPCCPU *cpu, 
> target_ulong hdecr,
>       ppc_tb_t *tb_env = cpu->env.tb_env;
>   
>       if (tb_env->hdecr_timer != NULL) {
> +        /* HDECR (Book3S 64bit) is edge-based, not level like DECR */
>           __cpu_ppc_store_decr(cpu, &tb_env->hdecr_next, tb_env->hdecr_timer,
>                                tb_env->hdecr_timer->cb, &cpu_ppc_hdecr_lower,
> +                             PPC_DECR_UNDERFLOW_TRIGGERED,
>                                hdecr, value, nr_bits);
>       }
>   }