[Intel-gfx] [PATCH] [v2] drm/i915/bdw: Add 42ms delay for IPS disable

[Ben Widawsky]

From: Ben Widawsky <benjamin.widawsky at linux.intel.com>

This is a requirement added to the spec. This patch will prevent
persistent corruption on the display.

v2: Make the wait before the vblank wait. (Art)
Try to finish early by polling the register
s/present/prevent (Chris)

Cc: Art Runyan <arthur.j.runyan at intel.com>
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/intel_display.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7f02444..05c60b1 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3583,10 +3583,13 @@ void hsw_disable_ips(struct intel_crtc *crtc)
 		return;
 
 	assert_plane_enabled(dev_priv, crtc->plane);
-	if (IS_BROADWELL(crtc->base.dev)) {
+	if (IS_BROADWELL(dev)) {
 		mutex_lock(&dev_priv->rps.hw_lock);
 		WARN_ON(sandybridge_pcode_write(dev_priv, DISPLAY_IPS_CONTROL, 0));
 		mutex_unlock(&dev_priv->rps.hw_lock);
+		/* wait for pcode to finish disabling IPS, which may take up to 42ms */
+		if (wait_for((I915_READ(IPS_CTL) & IPS_ENABLE) == 0, 42))
+			DRM_DEBUG_KMS("Timed out waiting for IPS disable\n");
 	} else {
 		I915_WRITE(IPS_CTL, 0);
 		POSTING_READ(IPS_CTL);
-- 
1.9.1