drm/i915/gen9: Sanitize handling of allowed DC states

We can simplify the conditions selecting the target DC state during
runtime by calculating the allowed DC states in advance during driver
loading. This also makes it easier to disable DC states depending on the
i915.disable_power_well module option, added in the next patch.

v2:
- Print a debug message if the requested max DC value was adjusted due
  to a platform limit. Also debug print the calculated mask value. (Patrik)

CC: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1456778945-5411-2-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -756,6 +756,7 @@ struct intel_csr {
 	i915_reg_t mmioaddr[8];
 	uint32_t mmiodata[8];
 	uint32_t dc_state;
+	uint32_t allowed_dc_mask;
 };
 
 #define DEV_INFO_FOR_EACH_FLAG(func, sep) \

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -538,12 +538,8 @@ static void gen9_set_dc_state(struct drm_i915_private *dev_priv, uint32_t state)
 	else
 		mask |= DC_STATE_EN_UPTO_DC6;
 
-	WARN_ON_ONCE(state & ~mask);
-
-	if (i915.enable_dc == 0)
-		state = DC_STATE_DISABLE;
-	else if (i915.enable_dc == 1 && state > DC_STATE_EN_UPTO_DC5)
-		state = DC_STATE_EN_UPTO_DC5;
+	if (WARN_ON_ONCE(state & ~dev_priv->csr.allowed_dc_mask))
+		state &= dev_priv->csr.allowed_dc_mask;
 
 	val = I915_READ(DC_STATE_EN);
 	DRM_DEBUG_KMS("Setting DC state from %02x to %02x\n",
@@ -659,8 +655,7 @@ static void gen9_disable_dc5_dc6(struct drm_i915_private *dev_priv)
 {
 	assert_can_disable_dc5(dev_priv);
 
-	if ((IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv)) &&
-	    i915.enable_dc != 0 && i915.enable_dc != 1)
+	if (dev_priv->csr.allowed_dc_mask & DC_STATE_EN_UPTO_DC6)
 		assert_can_disable_dc6(dev_priv);
 
 	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
@@ -839,26 +834,19 @@ static void gen9_dc_off_power_well_enable(struct drm_i915_private *dev_priv,
 static void gen9_dc_off_power_well_disable(struct drm_i915_private *dev_priv,
 					   struct i915_power_well *power_well)
 {
-	if ((IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv)) &&
-	    i915.enable_dc != 0 && i915.enable_dc != 1)
+	if (dev_priv->csr.allowed_dc_mask & DC_STATE_EN_UPTO_DC6)
 		skl_enable_dc6(dev_priv);
-	else
+	else if (dev_priv->csr.allowed_dc_mask & DC_STATE_EN_UPTO_DC5)
 		gen9_enable_dc5(dev_priv);
 }
 
 static void gen9_dc_off_power_well_sync_hw(struct drm_i915_private *dev_priv,
 					   struct i915_power_well *power_well)
 {
-	if (power_well->count > 0) {
-		gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
-	} else {
-		if ((IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv)) &&
-		    i915.enable_dc != 0 &&
-		    i915.enable_dc != 1)
-			gen9_set_dc_state(dev_priv, DC_STATE_EN_UPTO_DC6);
-		else
-			gen9_set_dc_state(dev_priv, DC_STATE_EN_UPTO_DC5);
-	}
+	if (power_well->count > 0)
+		gen9_dc_off_power_well_enable(dev_priv, power_well);
+	else
+		gen9_dc_off_power_well_disable(dev_priv, power_well);
 }
 
 static void i9xx_always_on_power_well_noop(struct drm_i915_private *dev_priv,
@@ -2023,6 +2011,52 @@ sanitize_disable_power_well_option(const struct drm_i915_private *dev_priv,
 	return 1;
 }
 
+static uint32_t get_allowed_dc_mask(const struct drm_i915_private *dev_priv,
+				    int enable_dc)
+{
+	uint32_t mask;
+	int requested_dc;
+	int max_dc;
+
+	if (IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv)) {
+		max_dc = 2;
+		mask = 0;
+	} else if (IS_BROXTON(dev_priv)) {
+		max_dc = 1;
+		/*
+		 * DC9 has a separate HW flow from the rest of the DC states,
+		 * not depending on the DMC firmware. It's needed by system
+		 * suspend/resume, so allow it unconditionally.
+		 */
+		mask = DC_STATE_EN_DC9;
+	} else {
+		max_dc = 0;
+		mask = 0;
+	}
+
+	if (enable_dc >= 0 && enable_dc <= max_dc) {
+		requested_dc = enable_dc;
+	} else if (enable_dc == -1) {
+		requested_dc = max_dc;
+	} else if (enable_dc > max_dc && enable_dc <= 2) {
+		DRM_DEBUG_KMS("Adjusting requested max DC state (%d->%d)\n",
+			      enable_dc, max_dc);
+		requested_dc = max_dc;
+	} else {
+		DRM_ERROR("Unexpected value for enable_dc (%d)\n", enable_dc);
+		requested_dc = max_dc;
+	}
+
+	if (requested_dc > 1)
+		mask |= DC_STATE_EN_UPTO_DC6;
+	if (requested_dc > 0)
+		mask |= DC_STATE_EN_UPTO_DC5;
+
+	DRM_DEBUG_KMS("Allowed DC state mask %02x\n", mask);
+
+	return mask;
+}
+
 #define set_power_wells(power_domains, __power_wells) ({		\
 	(power_domains)->power_wells = (__power_wells);			\
 	(power_domains)->power_well_count = ARRAY_SIZE(__power_wells);	\
@@ -2041,6 +2075,8 @@ int intel_power_domains_init(struct drm_i915_private *dev_priv)
 
 	i915.disable_power_well = sanitize_disable_power_well_option(dev_priv,
 						     i915.disable_power_well);
+	dev_priv->csr.allowed_dc_mask = get_allowed_dc_mask(dev_priv,
+							    i915.enable_dc);
 
 	BUILD_BUG_ON(POWER_DOMAIN_NUM > 31);