Re: [PATCH 03/12] drm/i915: Simplify VLV drain latency computation

Jesse Barnes
2015-02-27T17:47:31Z

On 02/10/2015 05:28 AM, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> The current drain lantency computation relies on hardcoded limits to
> determine when the to use the low vs. high precision multiplier.
> Rewrite the code to use a more straightforward approach.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 0f0281a..d6c6c1b 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -727,12 +727,15 @@ static bool vlv_compute_drain_latency(struct drm_crtc *crtc,
> return false;
>
> entries = DIV_ROUND_UP(clock, 1000) * pixel_size;
> - if (IS_CHERRYVIEW(dev))
> - *prec_mult = (entries > 32) ? 16 : 8;
> - else
> - *prec_mult = (entries > 128) ? 64 : 32;
> +
> + *prec_mult = IS_CHERRYVIEW(dev) ? 16 : 64;
> *drain_latency = (64 * (*prec_mult) * 4) / entries;
>
> + if (*drain_latency > DRAIN_LATENCY_MASK) {
> + *prec_mult /= 2;
> + *drain_latency = (64 * (*prec_mult) * 4) / entries;
> + }
> +
> if (*drain_latency > DRAIN_LATENCY_MASK)
> *drain_latency = DRAIN_LATENCY_MASK;
>
>

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>