Re: [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61

["Andreas Färber" <afaerber@suse.de>]

Am 10.06.2013 09:55, schrieb Bharat Bhushan:
> QEMU timer supports a maximum timer of INT64_MAX. So starting timer only for
> time which is calculated using target_bit < 62 and deactivate/stop timer if
> the target bit is above 61.
> 
> This patch also fix the time calculation from target_bit.
> The code was doing (1 << (target_bit + 1)) while this
> should be (1ULL << (target_bit + 1)).
> 
> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> ---
> v1->v2
>  - Added "booke: timer:" in patch subject
> 
>  hw/ppc/ppc_booke.c |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/ppc/ppc_booke.c b/hw/ppc/ppc_booke.c
> index e41b036..f4eda15 100644
> --- a/hw/ppc/ppc_booke.c
> +++ b/hw/ppc/ppc_booke.c
> @@ -133,9 +133,15 @@ static void booke_update_fixed_timer(CPUPPCState         *env,
>      ppc_tb_t *tb_env = env->tb_env;
>      uint64_t lapse;
>      uint64_t tb;
> -    uint64_t period = 1 << (target_bit + 1);
> +    uint64_t period;
>      uint64_t now;
>  
> +    /* Deactivate timer for target_bit > 61 */
> +    if (target_bit > 61)
> +        return; 

Braces missing and trailing whitespace after return.

So IIUC we can only allow 63 bits due to signedness, thus a maximum of
(1 << 62), thus target_bit <= 61.

Any chance at least the comment can be worded to explain that any
better? Maybe also use (target-bit + 1 >= 63) or period > INT64_MAX as
condition?

Best regards,
Andreas

> +
> +    period = 1ULL << (target_bit + 1);
> +
>      now = qemu_get_clock_ns(vm_clock);
>      tb  = cpu_ppc_get_tb(tb_env, now, tb_env->tb_offset);
>  
> 


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