drm/i915/bxt: Sanitiy check the PHY lane power down status

We can check the power state of the PHY data and common lanes as
reported by the PHY. Do this in case we need to debug problems where the
PHY gets stuck in an unexpected state.

Note that I only check these when the lanes are expected to be powered
on purpose, since it's not clear at what point the PHY power/clock gates
things.

v2:
- Don't report the encoder as disabled when the sanity check fails.
  (Ville)

CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465825477-32671-1-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -1279,6 +1279,15 @@ enum skl_disp_power_wells {
 #define BXT_P_CR_GT_DISP_PWRON		_MMIO(0x138090)
 #define   GT_DISPLAY_POWER_ON(phy)	(1 << (phy))
 
+#define _BXT_PHY_CTL_DDI_A		0x64C00
+#define _BXT_PHY_CTL_DDI_B		0x64C10
+#define _BXT_PHY_CTL_DDI_C		0x64C20
+#define   BXT_PHY_CMNLANE_POWERDOWN_ACK	(1 << 10)
+#define   BXT_PHY_LANE_POWERDOWN_ACK	(1 << 9)
+#define   BXT_PHY_LANE_ENABLED		(1 << 8)
+#define BXT_PHY_CTL(port)		_MMIO_PORT(port, _BXT_PHY_CTL_DDI_A, \
+							 _BXT_PHY_CTL_DDI_B)
+
 #define _PHY_CTL_FAMILY_EDP		0x64C80
 #define _PHY_CTL_FAMILY_DDI		0x64C90
 #define   COMMON_RESET_DIS		(1 << 31)

drivers/gpu/drm/i915/intel_ddi.c

@@ -1342,6 +1342,14 @@ bool intel_ddi_get_hw_state(struct intel_encoder *encoder,
 	DRM_DEBUG_KMS("No pipe for ddi port %c found\n", port_name(port));
 
 out:
+	if (ret && IS_BROXTON(dev_priv)) {
+		tmp = I915_READ(BXT_PHY_CTL(port));
+		if ((tmp & (BXT_PHY_LANE_POWERDOWN_ACK |
+			    BXT_PHY_LANE_ENABLED)) != BXT_PHY_LANE_ENABLED)
+			DRM_ERROR("Port %c enabled but PHY powered down? "
+				  "(PHY_CTL %08x)\n", port_name(port), tmp);
+	}
+
 	intel_display_power_put(dev_priv, power_domain);
 
 	return ret;
@@ -1745,6 +1753,8 @@ static void intel_disable_ddi(struct intel_encoder *intel_encoder)
 bool bxt_ddi_phy_is_enabled(struct drm_i915_private *dev_priv,
 			    enum dpio_phy phy)
 {
+	enum port port;
+
 	if (!(I915_READ(BXT_P_CR_GT_DISP_PWRON) & GT_DISPLAY_POWER_ON(phy)))
 		return false;
 
@@ -1770,6 +1780,21 @@ bool bxt_ddi_phy_is_enabled(struct drm_i915_private *dev_priv,
 		return false;
 	}
 
+	for_each_port_masked(port,
+			     phy == DPIO_PHY0 ? BIT(PORT_B) | BIT(PORT_C) :
+						BIT(PORT_A)) {
+		u32 tmp = I915_READ(BXT_PHY_CTL(port));
+
+		if (tmp & BXT_PHY_CMNLANE_POWERDOWN_ACK) {
+			DRM_DEBUG_DRIVER("DDI PHY %d powered, but common lane "
+					 "for port %c powered down "
+					 "(PHY_CTL %08x)\n",
+					 phy, port_name(port), tmp);
+
+			return false;
+		}
+	}
+
 	return true;
 }