[PATCH] drm/i915: implement WaIssueDummyWriteToWakeupFromRC6

Daniel Vetter
2012-10-18T11:56:23Z

Or at least our best understanding of it.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/gpu/drm/i915/i915_drv.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index a7837e5..c3f4f04 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)
+{
+ /* Ilk w/a: 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 { \
--
1.7.10.4