Re: [PATCH v2] drm/i915: Don't apply the 16Gb DIMM wm latency w/a to BXT/GLK

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Oct 24, 2018 at 12:05:40PM +0530, Mahesh Kumar wrote:
> LGTM..
> Reviewed-by: Mahesh Kumar <mahesh1.sh.kumar@gmail.com>

Thanks for the reviews. Pushed to dinq.

> 
> -Mahesh
> On Tue, Oct 23, 2018 at 11:52 PM Ville Syrjala
> <ville.syrjala@linux.intel.com> wrote:
> >
> > From: Ville Syrjälä <ville.syrjala@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.
> >
> > v2: Do the check when populating is_16gb_dimm (Mahesh)
> >
> > Cc: Mahesh Kumar <mahesh1.kumar@intel.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Fixes: 86b592876cb6 ("drm/i915: Implement 16GB dimm wa for latency level-0")
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.c | 15 ++++++++-------
> >  drivers/gpu/drm/i915/i915_drv.h |  1 -
> >  drivers/gpu/drm/i915/intel_pm.c |  3 +--
> >  3 files changed, 9 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > index baac35f698f9..6571044c9286 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -1165,8 +1165,6 @@ skl_dram_get_channels_info(struct drm_i915_private *dev_priv)
> >                 return -EINVAL;
> >         }
> >
> > -       dram_info->valid_dimm = true;
> > -
> >         /*
> >          * If any of the channel is single rank channel, worst case output
> >          * will be same as if single rank memory, so consider single rank
> > @@ -1183,8 +1181,7 @@ skl_dram_get_channels_info(struct drm_i915_private *dev_priv)
> >                 return -EINVAL;
> >         }
> >
> > -       if (ch0.is_16gb_dimm || ch1.is_16gb_dimm)
> > -               dram_info->is_16gb_dimm = true;
> > +       dram_info->is_16gb_dimm = ch0.is_16gb_dimm || ch1.is_16gb_dimm;
> >
> >         dev_priv->dram_info.symmetric_memory = intel_is_dram_symmetric(val_ch0,
> >                                                                        val_ch1,
> > @@ -1304,7 +1301,6 @@ bxt_get_dram_info(struct drm_i915_private *dev_priv)
> >                 return -EINVAL;
> >         }
> >
> > -       dram_info->valid_dimm = true;
> >         dram_info->valid = true;
> >         return 0;
> >  }
> > @@ -1317,12 +1313,17 @@ intel_get_dram_info(struct drm_i915_private *dev_priv)
> >         int ret;
> >
> >         dram_info->valid = false;
> > -       dram_info->valid_dimm = false;
> > -       dram_info->is_16gb_dimm = false;
> >         dram_info->rank = I915_DRAM_RANK_INVALID;
> >         dram_info->bandwidth_kbps = 0;
> >         dram_info->num_channels = 0;
> >
> > +       /*
> > +        * Assume 16Gb DIMMs are present until proven otherwise.
> > +        * This is only used for the level 0 watermark latency
> > +        * w/a which does not apply to bxt/glk.
> > +        */
> > +       dram_info->is_16gb_dimm = !IS_GEN9_LP(dev_priv);
> > +
> >         if (INTEL_GEN(dev_priv) < 9 || IS_GEMINILAKE(dev_priv))
> >                 return;
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 22cf3c75558c..2d7761b8ac07 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -1933,7 +1933,6 @@ struct drm_i915_private {
> >
> >         struct dram_info {
> >                 bool valid;
> > -               bool valid_dimm;
> >                 bool is_16gb_dimm;
> >                 u8 num_channels;
> >                 enum dram_rank {
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index 67a4d0735291..faef7f528269 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -2881,8 +2881,7 @@ 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 (dev_priv->dram_info.is_16gb_dimm)
> >                         wm[0] += 1;
> >
> >         } else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
> > --
> > 2.18.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel
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