drm/i915: Trim the ironlake+ irq handler

Ever noticed that our interrupt handlers are where we spend most of our
time on a busy system? In part this is unavoidable as each interrupt
requires to poll and reset several registers, but we can try and do so as
efficiently as possible.

Function                                     old     new   delta
ilk_irq_handler                             2317    2156    -161

v2: Restore the irqreturn_t ret

Function                                     old     new   delta
ilk_irq_handler.cold                          63      72      +9
ilk_irq_handler                             2221    2080    -141

A slight improvement in the baseline overnight as well!
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200601140355.20243-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_irq.c

@@ -2097,67 +2097,68 @@ static void ivb_display_irq_handler(struct drm_i915_private *dev_priv,
  */
 static irqreturn_t ilk_irq_handler(int irq, void *arg)
 {
-	struct drm_i915_private *dev_priv = arg;
+	struct drm_i915_private *i915 = arg;
+	void __iomem * const regs = i915->uncore.regs;
 	u32 de_iir, gt_iir, de_ier, sde_ier = 0;
 	irqreturn_t ret = IRQ_NONE;
 
-	if (!intel_irqs_enabled(dev_priv))
+	if (unlikely(!intel_irqs_enabled(i915)))
 		return IRQ_NONE;
 
 	/* IRQs are synced during runtime_suspend, we don't require a wakeref */
-	disable_rpm_wakeref_asserts(&dev_priv->runtime_pm);
+	disable_rpm_wakeref_asserts(&i915->runtime_pm);
 
 	/* disable master interrupt before clearing iir  */
-	de_ier = I915_READ(DEIER);
-	I915_WRITE(DEIER, de_ier & ~DE_MASTER_IRQ_CONTROL);
+	de_ier = raw_reg_read(regs, DEIER);
+	raw_reg_write(regs, DEIER, de_ier & ~DE_MASTER_IRQ_CONTROL);
 
 	/* Disable south interrupts. We'll only write to SDEIIR once, so further
 	 * interrupts will will be stored on its back queue, and then we'll be
 	 * able to process them after we restore SDEIER (as soon as we restore
 	 * it, we'll get an interrupt if SDEIIR still has something to process
 	 * due to its back queue). */
-	if (!HAS_PCH_NOP(dev_priv)) {
-		sde_ier = I915_READ(SDEIER);
-		I915_WRITE(SDEIER, 0);
+	if (!HAS_PCH_NOP(i915)) {
+		sde_ier = raw_reg_read(regs, SDEIER);
+		raw_reg_write(regs, SDEIER, 0);
 	}
 
 	/* Find, clear, then process each source of interrupt */
 
-	gt_iir = I915_READ(GTIIR);
+	gt_iir = raw_reg_read(regs, GTIIR);
 	if (gt_iir) {
-		I915_WRITE(GTIIR, gt_iir);
-		ret = IRQ_HANDLED;
-		if (INTEL_GEN(dev_priv) >= 6)
-			gen6_gt_irq_handler(&dev_priv->gt, gt_iir);
+		raw_reg_write(regs, GTIIR, gt_iir);
+		if (INTEL_GEN(i915) >= 6)
+			gen6_gt_irq_handler(&i915->gt, gt_iir);
 		else
-			gen5_gt_irq_handler(&dev_priv->gt, gt_iir);
+			gen5_gt_irq_handler(&i915->gt, gt_iir);
+		ret = IRQ_HANDLED;
 	}
 
-	de_iir = I915_READ(DEIIR);
+	de_iir = raw_reg_read(regs, DEIIR);
 	if (de_iir) {
-		I915_WRITE(DEIIR, de_iir);
-		ret = IRQ_HANDLED;
-		if (INTEL_GEN(dev_priv) >= 7)
-			ivb_display_irq_handler(dev_priv, de_iir);
+		raw_reg_write(regs, DEIIR, de_iir);
+		if (INTEL_GEN(i915) >= 7)
+			ivb_display_irq_handler(i915, de_iir);
 		else
-			ilk_display_irq_handler(dev_priv, de_iir);
+			ilk_display_irq_handler(i915, de_iir);
+		ret = IRQ_HANDLED;
 	}
 
-	if (INTEL_GEN(dev_priv) >= 6) {
-		u32 pm_iir = I915_READ(GEN6_PMIIR);
+	if (INTEL_GEN(i915) >= 6) {
+		u32 pm_iir = raw_reg_read(regs, GEN6_PMIIR);
 		if (pm_iir) {
-			I915_WRITE(GEN6_PMIIR, pm_iir);
+			raw_reg_write(regs, GEN6_PMIIR, pm_iir);
+			gen6_rps_irq_handler(&i915->gt.rps, pm_iir);
 			ret = IRQ_HANDLED;
-			gen6_rps_irq_handler(&dev_priv->gt.rps, pm_iir);
 		}
 	}
 
-	I915_WRITE(DEIER, de_ier);
-	if (!HAS_PCH_NOP(dev_priv))
-		I915_WRITE(SDEIER, sde_ier);
+	raw_reg_write(regs, DEIER, de_ier);
+	if (sde_ier)
+		raw_reg_write(regs, SDEIER, sde_ier);
 
 	/* IRQs are synced during runtime_suspend, we don't require a wakeref */
-	enable_rpm_wakeref_asserts(&dev_priv->runtime_pm);
+	enable_rpm_wakeref_asserts(&i915->runtime_pm);
 
 	return ret;
 }