Re: [Qemu-devel] [PATCHv2 08/12] cuda: factor out timebase-derived counter value and load time

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Feb 09, 2018 at 06:51:38PM +0000, Mark Cave-Ayland wrote:
> Commit b981289c49 "PPC: Cuda: Use cuda timer to expose tbfreq to guest" altered
> the timer calculations from those based upon the hardware CUDA clock frequency
> to those based upon the CPU timebase frequency.
> 
> In fact we can isolate the differences to 2 simple changes: one to the counter
> read value and another to the counter load time. Move these changes into
> separate functions so the implementation can be swapped later.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Applied, thanks.

> ---
>  hw/misc/macio/cuda.c | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/misc/macio/cuda.c b/hw/misc/macio/cuda.c
> index e00df4a21a..a185252144 100644
> --- a/hw/misc/macio/cuda.c
> +++ b/hw/misc/macio/cuda.c
> @@ -145,21 +145,29 @@ static void cuda_update_irq(CUDAState *s)
>      }
>  }
>  
> -static uint64_t get_tb(uint64_t time, uint64_t freq)
> +static uint64_t get_counter_value(CUDAState *s, CUDATimer *ti)
>  {
> -    return muldiv64(time, freq, NANOSECONDS_PER_SECOND);
> +    /* Reverse of the tb calculation algorithm that Mac OS X uses on bootup */
> +    uint64_t tb_diff = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
> +                                s->tb_frequency, NANOSECONDS_PER_SECOND) -
> +                           ti->load_time;
> +
> +    return (tb_diff * 0xBF401675E5DULL) / (s->tb_frequency << 24);
> +}
> +
> +static uint64_t get_counter_load_time(CUDAState *s, CUDATimer *ti)
> +{
> +    uint64_t load_time = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
> +                                  s->tb_frequency, NANOSECONDS_PER_SECOND);
> +    return load_time;
>  }
>  
>  static unsigned int get_counter(CUDAState *s, CUDATimer *ti)
>  {
>      int64_t d;
>      unsigned int counter;
> -    uint64_t tb_diff;
> -    uint64_t current_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>  
> -    /* Reverse of the tb calculation algorithm that Mac OS X uses on bootup. */
> -    tb_diff = get_tb(current_time, s->tb_frequency) - ti->load_time;
> -    d = (tb_diff * 0xBF401675E5DULL) / (s->tb_frequency << 24);
> +    d = get_counter_value(s, ti);
>  
>      if (ti->index == 0) {
>          /* the timer goes down from latch to -1 (period of latch + 2) */
> @@ -178,8 +186,7 @@ static unsigned int get_counter(CUDAState *s, CUDATimer *ti)
>  static void set_counter(CUDAState *s, CUDATimer *ti, unsigned int val)
>  {
>      CUDA_DPRINTF("T%d.counter=%d\n", 1 + ti->index, val);
> -    ti->load_time = get_tb(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
> -                           s->tb_frequency);
> +    ti->load_time = get_counter_load_time(s, ti);
>      ti->counter_value = val;
>      cuda_timer_update(s, ti, ti->load_time);
>  }

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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