[Intel-gfx] [PATCH] drm/i915: Don't apply the 16Gb DIMM wm latency w/a to BXT/GLK

[Mahesh Kumar]

Hi,

On Wed, Oct 10, 2018 at 11:25 PM Ville Syrjala
<ville.syrjala at linux.intel.com> wrote:
>
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> The 16Gb DIMM w/a is not applicable to BXT or GLK. Limit it to
> the appropriate platforms.
>
> This was especially harsh on GLK since we don't even try to read
> the DIMM information on that platforms, hence valid_dimm was
> always false and thus we always tried to apply the w/a.
> Furthermore the w/a pushed the level 0 latency above the
> level 1 latency, which doesn't really make sense.
>
> Cc: Mahesh Kumar <mahesh1.kumar at intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Fixes: 86b592876cb6 ("drm/i915: Implement 16GB dimm wa for latency level-0")
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 1392aa56a55a..a51cd09bbf75 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2881,8 +2881,9 @@ static void intel_read_wm_latency(struct drm_i915_private *dev_priv,
>                  * any underrun. If not able to get Dimm info assume 16GB dimm
>                  * to avoid any underrun.
>                  */
> -               if (!dev_priv->dram_info.valid_dimm ||
> -                   dev_priv->dram_info.is_16gb_dimm)
> +               if (!IS_GEN9_LP(dev_priv) &&
> +                   (!dev_priv->dram_info.valid_dimm ||
> +                    dev_priv->dram_info.is_16gb_dimm))
>                         wm[0] += 1;

I would rather prefer to update "intel_get_dram_info"  to fill
valid_dimm and is_16gb_dimm info properly

-       if (INTEL_GEN(dev_priv) < 9 || IS_GEMINILAKE(dev_priv))
+       if (INTEL_GEN(dev_priv) < 9 )
                return;

+       if (IS_GEN9_LP(dev_priv)) {
+               dram_info->valid_dimm = true;
+               dram_info->is_16gb_dimm = false;
+       }
+
+

-Mahesh

>
>         } else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
> --
> 2.18.1
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx