Re: [Qemu-devel] [PATCH v2 1/9] Add dummy implementation of generic timer cp15 registers

["Andreas Färber" <afaerber@suse.de>]

Am 24.01.2012 13:39, schrieb Peter Maydell:
> Add a dummy implementation of the cp15 registers for the generic
> timer (found in the Cortex-A15), just sufficient for Linux to
> decide that it can't use it. This requires at least CNTP_CTL and
> CNTFRQ to be implemented as RAZ/WI; we RAZ/WI all of c14.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target-arm/cpu.h    |    1 +
>  target-arm/helper.c |   12 ++++++++++--
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/target-arm/cpu.h b/target-arm/cpu.h
> index 42c53a7..d71d310 100644
> --- a/target-arm/cpu.h
> +++ b/target-arm/cpu.h
> @@ -382,6 +382,7 @@ enum arm_features {
>      ARM_FEATURE_VAPA, /* cp15 VA to PA lookups */
>      ARM_FEATURE_ARM_DIV, /* divide supported in ARM encoding */
>      ARM_FEATURE_VFP4, /* VFPv4 (implies that NEON is v2) */
> +    ARM_FEATURE_GENERICTIMER,

Personally I would've preferred GENERIC_TIMER (we have ARM_DIV,
THUMB_DIV as counterexamples), but no strong objection here.

Andreas

>  };
>  
>  static inline int arm_feature(CPUARMState *env, int feature)
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 00458fc..ecba0c6 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -1762,7 +1762,11 @@ void HELPER(set_cp15)(CPUState *env, uint32_t insn, uint32_t val)
>              goto bad_reg;
>          }
>          break;
> -    case 14: /* Reserved.  */
> +    case 14: /* Generic timer */
> +        if (arm_feature(env, ARM_FEATURE_GENERICTIMER)) {
> +            /* Dummy implementation: RAZ/WI for all */
> +            break;
> +        }
>          goto bad_reg;
>      case 15: /* Implementation specific.  */
>          if (arm_feature(env, ARM_FEATURE_XSCALE)) {
> @@ -2132,7 +2136,11 @@ uint32_t HELPER(get_cp15)(CPUState *env, uint32_t insn)
>          default:
>              goto bad_reg;
>          }
> -    case 14: /* Reserved.  */
> +    case 14: /* Generic timer */
> +        if (arm_feature(env, ARM_FEATURE_GENERICTIMER)) {
> +            /* Dummy implementation: RAZ/WI for all */
> +            return 0;
> +        }
>          goto bad_reg;
>      case 15: /* Implementation specific.  */
>          if (arm_feature(env, ARM_FEATURE_XSCALE)) {

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