[PATCH 3/4] drm/i915: Implement 16GB dimm wa for latency level-0

[Mahesh Kumar]

Memory with 16GB dimms require an increase of 1us in level-0 latency.
This patch implements the same.
Bspec: 4381

changes since V1:
 - make skl_is_16gb_dimm pure function

Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c | 41 +++++++++++++++++++++++++++++++++++++++--
 drivers/gpu/drm/i915/i915_drv.h |  2 ++
 drivers/gpu/drm/i915/intel_pm.c | 13 +++++++++++++
 3 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 80c68e1e9072..97e2fd0fd93e 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1076,8 +1076,28 @@ struct dram_channel_info {
 		enum dram_rank rank;
 	} l_info, s_info;
 	enum dram_rank rank;
+	bool is_16gb_dimm;
 };
 
+static bool
+skl_is_16gb_dimm(u8 rank, u8 size, u8 width)
+{
+	if (size == 16 && width == SKL_DRAM_WIDTH_X8 &&
+	    rank == SKL_DRAM_RANK_SINGLE)
+		return true;
+	else if (size == 32 && width == SKL_DRAM_WIDTH_X8 &&
+		 rank == SKL_DRAM_RANK_DUAL)
+		return true;
+	else if (size == 8 && width == SKL_DRAM_WIDTH_X16 &&
+		 rank == SKL_DRAM_RANK_SINGLE)
+		return true;
+	else if (size == 16 && width == SKL_DRAM_WIDTH_X16 &&
+		 rank == SKL_DRAM_RANK_DUAL)
+		return true;
+
+	return false;
+}
+
 static int
 skl_dram_get_channel_info(struct dram_channel_info *ch, u32 val)
 {
@@ -1085,6 +1105,7 @@ skl_dram_get_channel_info(struct dram_channel_info *ch, u32 val)
 	u8 l_size, s_size;
 	u8 l_width, s_width;
 	enum dram_rank rank;
+	bool l_16gb_dimm, s_16gb_dimm;
 
 	if (!val)
 		return -1;
@@ -1111,6 +1132,13 @@ skl_dram_get_channel_info(struct dram_channel_info *ch, u32 val)
 	else
 		rank = I915_DRAM_RANK_SINGLE;
 
+	l_16gb_dimm = skl_is_16gb_dimm(l_rank, l_size, l_width);
+	s_16gb_dimm = skl_is_16gb_dimm(s_rank, s_size, s_width);
+
+	if (l_16gb_dimm || s_16gb_dimm)
+		ch->is_16gb_dimm = true;
+	else
+		ch->is_16gb_dimm = false;
 	ch->l_info.size = l_size;
 	ch->s_info.size = s_size;
 	ch->l_info.width = l_width;
@@ -1145,6 +1173,8 @@ skl_get_mem_dimms_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
@@ -1160,6 +1190,10 @@ skl_get_mem_dimms_info(struct drm_i915_private *dev_priv)
 		DRM_INFO("couldn't get memory rank information\n");
 		return -EINVAL;
 	}
+
+	if (ch0.is_16gb_dimm || ch1.is_16gb_dimm)
+		dram_info->is_16gb_dimm = true;
+
 	return 0;
 }
 
@@ -1271,6 +1305,7 @@ bxt_get_dram_info(struct drm_i915_private *dev_priv)
 		return -EINVAL;
 	}
 
+	dram_info->valid_dimm = true;
 	dram_info->valid = true;
 	return 0;
 }
@@ -1283,6 +1318,8 @@ 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;
@@ -1306,9 +1343,9 @@ intel_get_dram_info(struct drm_i915_private *dev_priv)
 		sprintf(bandwidth_str, "unknown");
 	DRM_DEBUG_KMS("DRAM bandwidth:%s, total-channels: %u\n",
 		      bandwidth_str, dram_info->num_channels);
-	DRM_DEBUG_KMS("DRAM rank: %s rank\n",
+	DRM_DEBUG_KMS("DRAM rank: %s rank 16GB-dimm:%s\n",
 		      (dram_info->rank == I915_DRAM_RANK_DUAL) ?
-		      "dual" : "single");
+		      "dual" : "single", yesno(dram_info->is_16gb_dimm));
 }
 
 /**
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 46f942fa7d60..5a0d2abdb2ad 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1906,6 +1906,8 @@ struct drm_i915_private {
 
 	struct dram_info {
 		bool valid;
+		bool valid_dimm;
+		bool is_16gb_dimm;
 		u8 num_channels;
 		enum dram_rank {
 			I915_DRAM_RANK_INVALID = 0,
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 7312ecb73415..2446f53adf21 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2874,6 +2874,19 @@ static void intel_read_wm_latency(struct drm_i915_private *dev_priv,
 			}
 		}
 
+		/*
+		 * WA Level-0 adjustment for 16GB DIMMs: SKL+
+		 * If we could not get dimm info enable this WA to prevent from
+		 * any underrun. If not able to get Dimm info assume 16GB dimm
+		 * to avoid any underrun.
+		 */
+		if (dev_priv->dram_info.valid_dimm) {
+			if (dev_priv->dram_info.is_16gb_dimm)
+				wm[0] += 1;
+		} else {
+			wm[0] += 1;
+		}
+
 	} else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
 		uint64_t sskpd = I915_READ64(MCH_SSKPD);
 
-- 
2.16.2