drm/i915/bxt: Fix sanity check for BIOS RC6 setup

BXT BIOS has two options related to GPU power management: "RC6(Render
Standby)" and "GT PM Support". The assumption so far was that disabling
either of these options would leave RC6 uninitialized. According to my
tests this isn't so: for a proper RC6 setup we only need the "GT PM
Support" option to be enabled while the "RC6" option only controls
whether RC6 is left enabled or not by BIOS. OTOH we were missing a few
checks to ensure a proper RC6 setup. Add these now and don't fail the
sanity check if RC6 is disabled. This fixes a problem where RC6 remains
disabled after reloading the driver, since we explicitly disable RC6
during unloading.

v2:
- Print a debug message about the BIOS enabled RC state. (Sagar)

CC: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467216835-1086-2-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -7070,7 +7070,8 @@ enum {
 #define GEN6_RPDEUC				_MMIO(0xA084)
 #define GEN6_RPDEUCSW				_MMIO(0xA088)
 #define GEN6_RC_STATE				_MMIO(0xA094)
-#define   RC6_STATE				(1 << 18)
+#define   RC_SW_TARGET_STATE_SHIFT		16
+#define   RC_SW_TARGET_STATE_MASK		(7 << RC_SW_TARGET_STATE_SHIFT)
 #define GEN6_RC1_WAKE_RATE_LIMIT		_MMIO(0xA098)
 #define GEN6_RC6_WAKE_RATE_LIMIT		_MMIO(0xA09C)
 #define GEN6_RC6pp_WAKE_RATE_LIMIT		_MMIO(0xA0A0)
@@ -7085,12 +7086,16 @@ enum {
 #define GEN6_RC6pp_THRESHOLD			_MMIO(0xA0C0)
 #define GEN6_PMINTRMSK				_MMIO(0xA168)
 #define   GEN8_PMINTR_REDIRECT_TO_NON_DISP	(1<<31)
+#define GEN8_MISC_CTRL0				_MMIO(0xA180)
 #define VLV_PWRDWNUPCTL				_MMIO(0xA294)
 #define GEN9_MEDIA_PG_IDLE_HYSTERESIS		_MMIO(0xA0C4)
 #define GEN9_RENDER_PG_IDLE_HYSTERESIS		_MMIO(0xA0C8)
 #define GEN9_PG_ENABLE				_MMIO(0xA210)
 #define GEN9_RENDER_PG_ENABLE			(1<<0)
 #define GEN9_MEDIA_PG_ENABLE			(1<<1)
+#define GEN8_PUSHBUS_CONTROL			_MMIO(0xA248)
+#define GEN8_PUSHBUS_ENABLE			_MMIO(0xA250)
+#define GEN8_PUSHBUS_SHIFT			_MMIO(0xA25C)
 
 #define VLV_CHICKEN_3				_MMIO(VLV_DISPLAY_BASE + 0x7040C)
 #define  PIXEL_OVERLAP_CNT_MASK			(3 << 30)

drivers/gpu/drm/i915/intel_pm.c

@@ -4989,6 +4989,17 @@ static bool bxt_check_bios_rc6_setup(struct drm_i915_private *dev_priv)
 	struct i915_ggtt *ggtt = &dev_priv->ggtt;
 	bool enable_rc6 = true;
 	unsigned long rc6_ctx_base;
+	u32 rc_ctl;
+	int rc_sw_target;
+
+	rc_ctl = I915_READ(GEN6_RC_CONTROL);
+	rc_sw_target = (I915_READ(GEN6_RC_STATE) & RC_SW_TARGET_STATE_MASK) >>
+		       RC_SW_TARGET_STATE_SHIFT;
+	DRM_DEBUG_DRIVER("BIOS enabled RC states: "
+			 "HW_CTRL %s HW_RC6 %s SW_TARGET_STATE %x\n",
+			 onoff(rc_ctl & GEN6_RC_CTL_HW_ENABLE),
+			 onoff(rc_ctl & GEN6_RC_CTL_RC6_ENABLE),
+			 rc_sw_target);
 
 	if (!(I915_READ(RC6_LOCATION) & RC6_CTX_IN_DRAM)) {
 		DRM_DEBUG_DRIVER("RC6 Base location not set properly.\n");
@@ -5015,11 +5026,20 @@ static bool bxt_check_bios_rc6_setup(struct drm_i915_private *dev_priv)
 		enable_rc6 = false;
 	}
 
-	if (!(I915_READ(GEN6_RC_CONTROL) & (GEN6_RC_CTL_RC6_ENABLE |
-					    GEN6_RC_CTL_HW_ENABLE)) &&
-	    ((I915_READ(GEN6_RC_CONTROL) & GEN6_RC_CTL_HW_ENABLE) ||
-	     !(I915_READ(GEN6_RC_STATE) & RC6_STATE))) {
-		DRM_DEBUG_DRIVER("HW/SW RC6 is not enabled by BIOS.\n");
+	if (!I915_READ(GEN8_PUSHBUS_CONTROL) ||
+	    !I915_READ(GEN8_PUSHBUS_ENABLE) ||
+	    !I915_READ(GEN8_PUSHBUS_SHIFT)) {
+		DRM_DEBUG_DRIVER("Pushbus not setup properly.\n");
+		enable_rc6 = false;
+	}
+
+	if (!I915_READ(GEN6_GFXPAUSE)) {
+		DRM_DEBUG_DRIVER("GFX pause not setup properly.\n");
+		enable_rc6 = false;
+	}
+
+	if (!I915_READ(GEN8_MISC_CTRL0)) {
+		DRM_DEBUG_DRIVER("GPM control not setup properly.\n");
 		enable_rc6 = false;
 	}