From: Ville Syrjälä <ville.syrj...@linux.intel.com>

For skl+ we disable all wm levels with a decreasing memory latency
value. Let's generalize the same code to work for all platoforms,
and let's use it for ilk-bdw as well since those platforms also
read the latency values from a scratch register.

v2: n*10 usec, rebase

Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 57 ++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 8820c59c56e4..c72d3fd71b6f 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2825,6 +2825,41 @@ hsw_compute_linetime_wm(const struct intel_crtc_state 
*cstate)
               PIPE_WM_LINETIME_TIME(linetime);
 }
 
+static void intel_sanitize_wm_latency(struct drm_i915_private *dev_priv,
+                                     u16 *wm)
+{
+       int level, num_levels = dev_priv->wm.num_levels;
+
+       /*
+        * If we don't have WM0 latency, assume
+        * 5 usec and disable all WM1+ levels.
+        * 5 usec seems like a safe(ish) fallback value.
+        */
+       if (WARN(wm[0] == 0, "WM0 memory latency value is zero")) {
+               intel_print_wm_latency(dev_priv, "Bad", wm);
+
+               wm[0] = 5 * 10;
+
+               for (level = 1; level < num_levels; level++)
+                       wm[level] = 0;
+               return;
+       }
+
+       /* Make sure the latencies are non-decreasing */
+       for (level = 1; level < num_levels; level++) {
+               if (wm[level] >= wm[level - 1])
+                       continue;
+
+               if (WARN(wm[level] != 0,
+                        "Decreasing WM memory latency value(s)"))
+                       intel_print_wm_latency(dev_priv, "Bad", wm);
+
+               for (; level < num_levels; level++)
+                       wm[level] = 0;
+               break;
+       }
+}
+
 static void ilk_read_wm_latency(struct drm_i915_private *dev_priv,
                                u16 wm[5])
 {
@@ -2934,6 +2969,10 @@ static void ilk_setup_wm_latency(struct drm_i915_private 
*dev_priv)
        ilk_fixup_spr_cur_wm_latency(dev_priv, dev_priv->wm.spr_latency);
        ilk_fixup_spr_cur_wm_latency(dev_priv, dev_priv->wm.cur_latency);
 
+       intel_sanitize_wm_latency(dev_priv, dev_priv->wm.pri_latency);
+       intel_sanitize_wm_latency(dev_priv, dev_priv->wm.spr_latency);
+       intel_sanitize_wm_latency(dev_priv, dev_priv->wm.cur_latency);
+
        intel_print_wm_latency(dev_priv, "Primary", dev_priv->wm.pri_latency);
        intel_print_wm_latency(dev_priv, "Sprite", dev_priv->wm.spr_latency);
        intel_print_wm_latency(dev_priv, "Cursor", dev_priv->wm.cur_latency);
@@ -2945,8 +2984,7 @@ static void ilk_setup_wm_latency(struct drm_i915_private 
*dev_priv)
 static void skl_read_wm_latency(struct drm_i915_private *dev_priv,
                                u16 wm[8])
 {
-       int level, num_levels = dev_priv->wm.num_levels;
-       int ret, i;
+       int ret;
        u32 val;
 
        /* read the first set of memory latencies[0:3] */
@@ -2989,19 +3027,6 @@ static void skl_read_wm_latency(struct drm_i915_private 
*dev_priv,
                GEN9_MEM_LATENCY_LEVEL_MASK;
        wm[7] = (val >> GEN9_MEM_LATENCY_LEVEL_3_7_SHIFT) &
                GEN9_MEM_LATENCY_LEVEL_MASK;
-
-       /*
-        * If a level n (n > 1) has a 0us latency, all levels m (m >= n)
-        * need to be disabled. We make sure to sanitize the values out
-        * of the punit to satisfy this requirement.
-        */
-       for (level = 1; level < num_levels; level++) {
-               if (wm[level] == 0) {
-                       for (i = level + 1; i < num_levels; i++)
-                               wm[i] = 0;
-                       break;
-               }
-       }
 }
 
 static void skl_fixup_wm_latency_units(struct drm_i915_private *dev_priv,
@@ -3056,6 +3081,8 @@ static void skl_setup_wm_latency(struct drm_i915_private 
*dev_priv)
 
        skl_wm_latency_wa(dev_priv, dev_priv->wm.pri_latency);
 
+       intel_sanitize_wm_latency(dev_priv, dev_priv->wm.pri_latency);
+
        memcpy(dev_priv->wm.spr_latency, dev_priv->wm.pri_latency,
               sizeof(dev_priv->wm.pri_latency));
        memcpy(dev_priv->wm.cur_latency, dev_priv->wm.pri_latency,
-- 
2.18.1

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