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

[Mahesh Kumar]

LGTM..
Reviewed-by: Mahesh Kumar <mahesh1.sh.kumar at gmail.com>

-Mahesh
On Tue, Oct 23, 2018 at 11:52 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.
>
> v2: Do the check when populating is_16gb_dimm (Mahesh)
>
> 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/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
>
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