[Intel-gfx] [PATCH 10/35] drm/i915: Don't multiply the watermark latency values too early

[Paulo Zanoni]

2013/7/5  <ville.syrjala at linux.intel.com>:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> The LP1+ watermark latency values need to be multiplied by 5 to
> make the suitable for watermark calculations. However on pre-HSW
> platforms we're going to need the raw value later when we have to
> write it to the WM_LPn registers' latency field. So delay the
> multiplication until it's needed.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

My only worry is that now we're hiding even more the measurement units
used for mem_value. Perhaps we could also patch hsw_compute_wm_pipe
and hsw_compute_lp_wm explaining that a mem_value of 1 means "100ns"?
Maybe a comment?

Anyway, the patch is correct, so: Reviewed-by: Paulo Zanoni
<paulo.r.zanonI at intel.com>

> ---
>  drivers/gpu/drm/i915/intel_pm.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index c266e47..a2ca018 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2346,10 +2346,10 @@ static void intel_read_wm_latency(struct drm_device *dev, uint16_t wm[5])
>                 wm[0] = (sskpd >> 56) & 0xFF;
>                 if (wm[0] == 0)
>                         wm[0] = sskpd & 0xF;
> -               wm[1] = ((sskpd >> 4) & 0xFF) * 5;
> -               wm[2] = ((sskpd >> 12) & 0xFF) * 5;
> -               wm[3] = ((sskpd >> 20) & 0x1FF) * 5;
> -               wm[4] = ((sskpd >> 32) & 0x1FF) * 5;
> +               wm[1] = (sskpd >> 4) & 0xFF;
> +               wm[2] = (sskpd >> 12) & 0xFF;
> +               wm[3] = (sskpd >> 20) & 0x1FF;
> +               wm[4] = (sskpd >> 32) & 0x1FF;
>         }
>  }
>
> @@ -2427,7 +2427,7 @@ static void hsw_compute_wm_results(struct drm_device *dev,
>         int level, max_level, wm_lp;
>
>         for (level = 1; level <= 4; level++)
> -               if (!hsw_compute_lp_wm(wm[level], lp_maximums, params,
> +               if (!hsw_compute_lp_wm(wm[level] * 5, lp_maximums, params,
>                                        &lp_results[level - 1]))
>                         break;
>         max_level = level - 1;
> --
> 1.8.1.5
>
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-- 
Paulo Zanoni