drm/i915: Fix DEIER and GTIER collecting for BDW.

BDW has many other Display Engine interrupts and GT interrupts registers.
Collecting it properly on gpu_error_state.

On debugfs all was properly listed already but besides we were also listing old
DEIER and GTIER that doesn't exist on BDW anymore. This was causing
unclaimed register messages

v2: Fix small issues of first version and don't read DEIER regs when pipe's
    power well is disabled
v3: bikeshed accepted: use enum pipe pipe instead of int i for pipe interection
v4: Ben notice previous version was checking for display_power_enabled without
    using propper locks. Using _unlocked version isn't reliable and we cannot
    get this registers when power well is off. So let's avoid getting all DE_IER
    per pipe for now. If someone think this is an useful information it can be
    added later.
v5: Ben: put back debugfs stuff that might be coverred by pm_get and use
    	 gen >= 8 trying to predict future.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=81701
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: (v3) Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -314,7 +314,7 @@ struct drm_i915_error_state {
 	u32 eir;
 	u32 pgtbl_er;
 	u32 ier;
-	u32 gtier;
+	u32 gtier[4];
 	u32 ccid;
 	u32 derrmr;
 	u32 forcewake;

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -361,8 +361,12 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
 	err_printf(m, "PCI ID: 0x%04x\n", dev->pdev->device);
 	err_printf(m, "EIR: 0x%08x\n", error->eir);
 	err_printf(m, "IER: 0x%08x\n", error->ier);
-	if (HAS_PCH_SPLIT(dev) || IS_VALLEYVIEW(dev))
-		err_printf(m, "GTIER: 0x%08x\n", error->gtier);
+	if (INTEL_INFO(dev)->gen >= 8) {
+		for (i = 0; i < 4; i++)
+			err_printf(m, "GTIER gt %d: 0x%08x\n", i,
+				   error->gtier[i]);
+	} else if (HAS_PCH_SPLIT(dev) || IS_VALLEYVIEW(dev))
+		err_printf(m, "GTIER: 0x%08x\n", error->gtier[0]);
 	err_printf(m, "PGTBL_ER: 0x%08x\n", error->pgtbl_er);
 	err_printf(m, "FORCEWAKE: 0x%08x\n", error->forcewake);
 	err_printf(m, "DERRMR: 0x%08x\n", error->derrmr);
@@ -1096,6 +1100,7 @@ static void i915_capture_reg_state(struct drm_i915_private *dev_priv,
 				   struct drm_i915_error_state *error)
 {
 	struct drm_device *dev = dev_priv->dev;
+	int i;
 
 	/* General organization
 	 * 1. Registers specific to a single generation
@@ -1107,7 +1112,7 @@ static void i915_capture_reg_state(struct drm_i915_private *dev_priv,
 
 	/* 1: Registers specific to a single generation */
 	if (IS_VALLEYVIEW(dev)) {
-		error->gtier = I915_READ(GTIER);
+		error->gtier[0] = I915_READ(GTIER);
 		error->ier = I915_READ(VLV_IER);
 		error->forcewake = I915_READ(FORCEWAKE_VLV);
 	}
@@ -1141,9 +1146,13 @@ static void i915_capture_reg_state(struct drm_i915_private *dev_priv,
 	if (HAS_HW_CONTEXTS(dev))
 		error->ccid = I915_READ(CCID);
 
-	if (HAS_PCH_SPLIT(dev)) {
+	if (INTEL_INFO(dev)->gen >= 8) {
+		error->ier = I915_READ(GEN8_DE_MISC_IER);
+		for (i = 0; i < 4; i++)
+			error->gtier[i] = I915_READ(GEN8_GT_IER(i));
+	} else if (HAS_PCH_SPLIT(dev)) {
 		error->ier = I915_READ(DEIER);
-		error->gtier = I915_READ(GTIER);
+		error->gtier[0] = I915_READ(GTIER);
 	} else if (IS_GEN2(dev)) {
 		error->ier = I915_READ16(IER);
 	} else if (!IS_VALLEYVIEW(dev)) {