drm/i915: Move SAGV block time to dev_priv

In prep for newer platforms having more complicated ways to determine
the SAGV block time, move the variable to dev_priv, and extract the
setting to an initial setup function. While we're at it, update the if
ladder to follow the new gen -> old gen order preference, and warn on
any non-specified gen.

v2: Shorten the function name (Ville), return directly (Ville), move
sagv_block_time_us value to dev_priv (Ville)

v3: Change sagv_block_time_us to u32 (Lucas), Change fallback value to
-1 (Lucas), use intel_has_sagv for setup check rather than hand-rolling
(Lucas)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: James Ausmus <james.ausmus@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191004221449.1317-1-james.ausmus@intel.com
Link: https://patchwork.freedesktop.org/patch/msgid/20191009172315.11004-1-lucas.demarchi@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -1267,6 +1267,8 @@ struct drm_i915_private {
 		I915_SAGV_NOT_CONTROLLED
 	} sagv_status;
 
+	u32 sagv_block_time_us;
+
 	struct {
 		/*
 		 * Raw watermark latency values:

drivers/gpu/drm/i915/intel_pm.c

@@ -3638,6 +3638,26 @@ intel_has_sagv(struct drm_i915_private *dev_priv)
 		dev_priv->sagv_status != I915_SAGV_NOT_CONTROLLED;
 }
 
+static void
+skl_setup_sagv_block_time(struct drm_i915_private *dev_priv)
+{
+	if (IS_GEN(dev_priv, 11)) {
+		dev_priv->sagv_block_time_us = 10;
+		return;
+	} else if (IS_GEN(dev_priv, 10)) {
+		dev_priv->sagv_block_time_us = 20;
+		return;
+	} else if (IS_GEN(dev_priv, 9)) {
+		dev_priv->sagv_block_time_us = 30;
+		return;
+	} else {
+		MISSING_CASE(INTEL_GEN(dev_priv));
+	}
+
+	/* Default to an unusable block time */
+	dev_priv->sagv_block_time_us = -1;
+}
+
 /*
  * SAGV dynamically adjusts the system agent voltage and clock frequencies
  * depending on power and performance requirements. The display engine access
@@ -3726,18 +3746,10 @@ bool intel_can_enable_sagv(struct intel_atomic_state *state)
 	struct intel_crtc_state *crtc_state;
 	enum pipe pipe;
 	int level, latency;
-	int sagv_block_time_us;
 
 	if (!intel_has_sagv(dev_priv))
 		return false;
 
-	if (IS_GEN(dev_priv, 9))
-		sagv_block_time_us = 30;
-	else if (IS_GEN(dev_priv, 10))
-		sagv_block_time_us = 20;
-	else
-		sagv_block_time_us = 10;
-
 	/*
 	 * If there are no active CRTCs, no additional checks need be performed
 	 */
@@ -3784,7 +3796,7 @@ bool intel_can_enable_sagv(struct intel_atomic_state *state)
 		 * incur memory latencies higher than sagv_block_time_us we
 		 * can't enable SAGV.
 		 */
-		if (latency < sagv_block_time_us)
+		if (latency < dev_priv->sagv_block_time_us)
 			return false;
 	}
 
@@ -8985,6 +8997,9 @@ void intel_init_pm(struct drm_i915_private *dev_priv)
 	else if (IS_GEN(dev_priv, 5))
 		i915_ironlake_get_mem_freq(dev_priv);
 
+	if (intel_has_sagv(dev_priv))
+		skl_setup_sagv_block_time(dev_priv);
+
 	/* For FIFO watermark updates */
 	if (INTEL_GEN(dev_priv) >= 9) {
 		skl_setup_wm_latency(dev_priv);