drm/i915: Reduce locking in gen8 IRQ handler

Similar in vain in reducing the number of unrequired spinlocks used for
execlist command submission (where the forcewake is required but
manually controlled), we know that the IRQ registers are outside of the
powerwell and so we can access them directly. Since we now have direct
access exported via I915_READ_FW/I915_WRITE_FW, lets put those to use in
the irq handlers as well.

In the process, reorder the execlist submission to happen as early as
possible.

v2: Restrict the untraced register mmio to just the GT path (i.e. the
hotpath for execlists)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -1285,74 +1285,74 @@ static irqreturn_t gen8_gt_irq_handler(struct drm_device *dev,
 	irqreturn_t ret = IRQ_NONE;
 
 	if (master_ctl & (GEN8_GT_RCS_IRQ | GEN8_GT_BCS_IRQ)) {
-		tmp = I915_READ(GEN8_GT_IIR(0));
+		tmp = I915_READ_FW(GEN8_GT_IIR(0));
 		if (tmp) {
-			I915_WRITE(GEN8_GT_IIR(0), tmp);
+			I915_WRITE_FW(GEN8_GT_IIR(0), tmp);
 			ret = IRQ_HANDLED;
 
 			rcs = tmp >> GEN8_RCS_IRQ_SHIFT;
 			ring = &dev_priv->ring[RCS];
-			if (rcs & GT_RENDER_USER_INTERRUPT)
-				notify_ring(dev, ring);
 			if (rcs & GT_CONTEXT_SWITCH_INTERRUPT)
 				intel_lrc_irq_handler(ring);
+			if (rcs & GT_RENDER_USER_INTERRUPT)
+				notify_ring(dev, ring);
 
 			bcs = tmp >> GEN8_BCS_IRQ_SHIFT;
 			ring = &dev_priv->ring[BCS];
-			if (bcs & GT_RENDER_USER_INTERRUPT)
-				notify_ring(dev, ring);
 			if (bcs & GT_CONTEXT_SWITCH_INTERRUPT)
 				intel_lrc_irq_handler(ring);
+			if (bcs & GT_RENDER_USER_INTERRUPT)
+				notify_ring(dev, ring);
 		} else
 			DRM_ERROR("The master control interrupt lied (GT0)!\n");
 	}
 
 	if (master_ctl & (GEN8_GT_VCS1_IRQ | GEN8_GT_VCS2_IRQ)) {
-		tmp = I915_READ(GEN8_GT_IIR(1));
+		tmp = I915_READ_FW(GEN8_GT_IIR(1));
 		if (tmp) {
-			I915_WRITE(GEN8_GT_IIR(1), tmp);
+			I915_WRITE_FW(GEN8_GT_IIR(1), tmp);
 			ret = IRQ_HANDLED;
 
 			vcs = tmp >> GEN8_VCS1_IRQ_SHIFT;
 			ring = &dev_priv->ring[VCS];
-			if (vcs & GT_RENDER_USER_INTERRUPT)
-				notify_ring(dev, ring);
 			if (vcs & GT_CONTEXT_SWITCH_INTERRUPT)
 				intel_lrc_irq_handler(ring);
+			if (vcs & GT_RENDER_USER_INTERRUPT)
+				notify_ring(dev, ring);
 
 			vcs = tmp >> GEN8_VCS2_IRQ_SHIFT;
 			ring = &dev_priv->ring[VCS2];
-			if (vcs & GT_RENDER_USER_INTERRUPT)
-				notify_ring(dev, ring);
 			if (vcs & GT_CONTEXT_SWITCH_INTERRUPT)
 				intel_lrc_irq_handler(ring);
+			if (vcs & GT_RENDER_USER_INTERRUPT)
+				notify_ring(dev, ring);
 		} else
 			DRM_ERROR("The master control interrupt lied (GT1)!\n");
 	}
 
 	if (master_ctl & GEN8_GT_PM_IRQ) {
-		tmp = I915_READ(GEN8_GT_IIR(2));
+		tmp = I915_READ_FW(GEN8_GT_IIR(2));
 		if (tmp & dev_priv->pm_rps_events) {
-			I915_WRITE(GEN8_GT_IIR(2),
-				   tmp & dev_priv->pm_rps_events);
+			I915_WRITE_FW(GEN8_GT_IIR(2),
+				      tmp & dev_priv->pm_rps_events);
 			ret = IRQ_HANDLED;
 			gen6_rps_irq_handler(dev_priv, tmp);
 		} else
 			DRM_ERROR("The master control interrupt lied (PM)!\n");
 	}
 
 	if (master_ctl & GEN8_GT_VECS_IRQ) {
-		tmp = I915_READ(GEN8_GT_IIR(3));
+		tmp = I915_READ_FW(GEN8_GT_IIR(3));
 		if (tmp) {
-			I915_WRITE(GEN8_GT_IIR(3), tmp);
+			I915_WRITE_FW(GEN8_GT_IIR(3), tmp);
 			ret = IRQ_HANDLED;
 
 			vcs = tmp >> GEN8_VECS_IRQ_SHIFT;
 			ring = &dev_priv->ring[VECS];
-			if (vcs & GT_RENDER_USER_INTERRUPT)
-				notify_ring(dev, ring);
 			if (vcs & GT_CONTEXT_SWITCH_INTERRUPT)
 				intel_lrc_irq_handler(ring);
+			if (vcs & GT_RENDER_USER_INTERRUPT)
+				notify_ring(dev, ring);
 		} else
 			DRM_ERROR("The master control interrupt lied (GT3)!\n");
 	}
@@ -2178,13 +2178,12 @@ static irqreturn_t gen8_irq_handler(int irq, void *arg)
 		aux_mask |=  GEN9_AUX_CHANNEL_B | GEN9_AUX_CHANNEL_C |
 			GEN9_AUX_CHANNEL_D;
 
-	master_ctl = I915_READ(GEN8_MASTER_IRQ);
+	master_ctl = I915_READ_FW(GEN8_MASTER_IRQ);
 	master_ctl &= ~GEN8_MASTER_IRQ_CONTROL;
 	if (!master_ctl)
 		return IRQ_NONE;
 
-	I915_WRITE(GEN8_MASTER_IRQ, 0);
-	POSTING_READ(GEN8_MASTER_IRQ);
+	I915_WRITE_FW(GEN8_MASTER_IRQ, 0);
 
 	/* Find, clear, then process each source of interrupt */
 
@@ -2281,8 +2280,8 @@ static irqreturn_t gen8_irq_handler(int irq, void *arg)
 
 	}
 
-	I915_WRITE(GEN8_MASTER_IRQ, GEN8_MASTER_IRQ_CONTROL);
-	POSTING_READ(GEN8_MASTER_IRQ);
+	I915_WRITE_FW(GEN8_MASTER_IRQ, GEN8_MASTER_IRQ_CONTROL);
+	POSTING_READ_FW(GEN8_MASTER_IRQ);
 
 	return ret;
 }