[Intel-gfx] [PATCH v2] drm/i915/perf: per-gen timebase for checking sample freq

[Matthew Auld]

On 5 April 2017 at 20:05, Robert Bragg <robert at sixbynine.org> wrote:
> An oa_exponent_to_ns() utility and per-gen timebase constants where
were

> recently removed when updating the tail pointer race condition WA, and
> this restores those so we can update the _PROP_OA_EXPONENT validation
> done in read_properties_unlocked() to not assume we have a 12.5MHz
> timebase as we did for Haswell.
>
> Accordingly the oa_sample_rate_hard_limit value that's referenced by
> proc_dointvec_minmax defining the absolute limit for the OA sampling
> frequency is now initialized to (timestamp_frequency / 2) instead of the
> 6.25MHz constant for Haswell.
>
> v2:
>     Specify frequency of 19.2MHz for BXT (Ville)
>     Initialize oa_sample_rate_hard_limit per-gen too (Lionel)
>
> Signed-off-by: Robert Bragg <robert at sixbynine.org>
> Cc: Lionel Landwerlin <lionel.g.landwerlin at linux.intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h  |  1 +
>  drivers/gpu/drm/i915/i915_perf.c | 31 ++++++++++++++++++++++---------
>  2 files changed, 23 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 3a22b6fd0ee6..48b07d706f06 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2463,6 +2463,7 @@ struct drm_i915_private {
>
>                         bool periodic;
>                         int period_exponent;
> +                       int timestamp_frequency;
>
>                         int metrics_set;
>
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 98eb6415b63a..980b4a1fd7cc 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -288,10 +288,12 @@ static u32 i915_perf_stream_paranoid = true;
>
>  /* For sysctl proc_dointvec_minmax of i915_oa_max_sample_rate
>   *
> - * 160ns is the smallest sampling period we can theoretically program the OA
> - * unit with on Haswell, corresponding to 6.25MHz.
> + * The highest sampling frequency we can theoretically program the OA unit
> + * with is always half the timestamp frequency: E.g. 6.25Mhz for Haswell.
> + *
> + * Initialized just before we register the sysctl parameter.
>   */
> -static int oa_sample_rate_hard_limit = 6250000;
> +static int oa_sample_rate_hard_limit;
>
>  /* Theoretically we can program the OA unit to sample every 160ns but don't
>   * allow that by default unless root...
> @@ -2549,6 +2551,12 @@ i915_perf_open_ioctl_locked(struct drm_i915_private *dev_priv,
>         return ret;
>  }
>
> +static u64 oa_exponent_to_ns(struct drm_i915_private *dev_priv, int exponent)
> +{
> +       return div_u64(1000000000ULL * (2ULL << exponent),
> +                      dev_priv->perf.oa.timestamp_frequency);
> +}
> +
>  /**
>   * read_properties_unlocked - validate + copy userspace stream open properties
>   * @dev_priv: i915 device instance
> @@ -2647,14 +2655,9 @@ static int read_properties_unlocked(struct drm_i915_private *dev_priv,
>                         /* Theoretically we can program the OA unit to sample
>                          * every 160ns but don't allow that by default unless
hmm, that's not actually true if we consider BXT, right?

Reviewed-by: Matthew Auld <matthew.auld at intel.com>