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

[Mahesh Kumar]

On Thu, Oct 11, 2018 at 2:19 AM Mahesh Kumar <mahesh1.sh.kumar at gmail.com> wrote:
>
> 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;
> +       }
> +
> +
We don't want to proceed for GLK. So, something like:

+       if (IS_GEN9_LP(dev_priv)) {
+               dram_info->valid_dimm = true;
+               dram_info->is_16gb_dimm = false;
+       }
+
        if (INTEL_GEN(dev_priv) < 9 || IS_GEMINILAKE(dev_priv))
                return;

-Mahesh
>
> -Mahesh
>
> >
> >         } else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
> > --
> > 2.18.1
> >
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