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

[Ville Syrjala]

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