drm/i915: disable IPS while getting the pipe CRCs.

For some yet-undiscovered reason, when IPS gets enabled, the pipe CRC
changes. Since hsw_enable_ips() doesn't really guarantees to enable
IPS (it depends on package C-states), we can't really predict if IPS
is enabled or disabled while running our CRC tests, so let's just
completely disable IPS while pipe CRCs are being used.

If we find a way to make IPS not change the pipe CRC result, we may
want to fix IPS and then revert this patch. While this doesn't happen,
let's merge this patch, so every IGT test relying on the CRCs can
work on pipe A.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=72864
Testcase: igt/kms_cursor_crc (and others)
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -3255,6 +3255,8 @@ static int pipe_crc_set_source(struct drm_device *dev, enum pipe pipe,
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_pipe_crc *pipe_crc = &dev_priv->pipe_crc[pipe];
+	struct intel_crtc *crtc = to_intel_crtc(intel_get_crtc_for_pipe(dev,
+									pipe));
 	u32 val = 0; /* shut up gcc */
 	int ret;
 
@@ -3290,6 +3292,14 @@ static int pipe_crc_set_source(struct drm_device *dev, enum pipe pipe,
 		if (!pipe_crc->entries)
 			return -ENOMEM;
 
+		/*
+		 * When IPS gets enabled, the pipe CRC changes. Since IPS gets
+		 * enabled and disabled dynamically based on package C states,
+		 * user space can't make reliable use of the CRCs, so let's just
+		 * completely disable it.
+		 */
+		hsw_disable_ips(crtc);
+
 		spin_lock_irq(&pipe_crc->lock);
 		pipe_crc->head = 0;
 		pipe_crc->tail = 0;
@@ -3328,6 +3338,8 @@ static int pipe_crc_set_source(struct drm_device *dev, enum pipe pipe,
 			vlv_undo_pipe_scramble_reset(dev, pipe);
 		else if (IS_HASWELL(dev) && pipe == PIPE_A)
 			hsw_undo_trans_edp_pipe_A_crc_wa(dev);
+
+		hsw_enable_ips(crtc);
 	}
 
 	return 0;