From: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Thu, 18 Oct 2012 12:16:09 +0000 (+0200)
Subject: drm/i915: implement WaIssueDummyWriteToWakeupFromRC6
X-Git-Tag: firefly_0821_release~3680^2~1383^2~193^2~91
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a8b1397d717e36abd9e45f8fee61d800f7d236ec;p=firefly-linux-kernel-4.4.55.git

drm/i915: implement WaIssueDummyWriteToWakeupFromRC6

Or at least our best understanding of it.

v2: Fixup commit message and put the wa name into the comment block.
And actually update the commit, too.

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

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 59dc4817964b..42388533708f 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1131,9 +1131,20 @@ static bool IS_DISPLAYREG(u32 reg)
 	return true;
 }
 
+static void
+ilk_dummy_write(struct drm_i915_private *dev_priv)
+{
+	/* WaIssueDummyWriteToWakeupFromRC6: Issue a dummy write to wake up the
+	 * chip from rc6 before touching it for real. MI_MODE is masked, hence
+	 * harmless to write 0 into. */
+	I915_WRITE_NOTRACE(MI_MODE, 0);
+}
+
 #define __i915_read(x, y) \
 u##x i915_read##x(struct drm_i915_private *dev_priv, u32 reg) { \
 	u##x val = 0; \
+	if (IS_GEN5(dev_priv->dev)) \
+		ilk_dummy_write(dev_priv); \
 	if (NEEDS_FORCE_WAKE((dev_priv), (reg))) { \
 		unsigned long irqflags; \
 		spin_lock_irqsave(&dev_priv->gt_lock, irqflags); \
@@ -1165,6 +1176,8 @@ void i915_write##x(struct drm_i915_private *dev_priv, u32 reg, u##x val) { \
 	if (NEEDS_FORCE_WAKE((dev_priv), (reg))) { \
 		__fifo_ret = __gen6_gt_wait_for_fifo(dev_priv); \
 	} \
+	if (IS_GEN5(dev_priv->dev)) \
+		ilk_dummy_write(dev_priv); \
 	if (IS_VALLEYVIEW(dev_priv->dev) && IS_DISPLAYREG(reg)) { \
 		write##y(val, dev_priv->regs + reg + 0x180000);		\
 	} else {							\