[PATCH 4/4] drm/i915: Make sure PSR is ready for been re-enabled.

[Rodrigo Vivi <rodrigo.vivi@gmail.com>]

Let's make sure PSR is propperly disabled before to re-enabled it.

According to Spec, after disabled PSR CTL, the Idle state might occur
up to 24ms, that is one full frame time (1/refresh rate),
plus SRD exit training time (max of 6ms),
plus SRD aux channel handshake (max of 1.5ms).

So if something went wrong PSR will be disabled until next full
enable/disable setup.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 2f0eee5..658a911 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1885,6 +1885,17 @@ static void intel_edp_psr_do_enable(struct intel_dp *intel_dp)
 	WARN_ON(dev_priv->psr.active);
 	lockdep_assert_held(&dev_priv->psr.lock);
 
+	/* We have to make sure PSR is ready for re-enable
+	 * otherwise it keeps disabled until next full enable/disable cycle.
+	 * PSR might take up to 24 ms to get fully disabled
+	 * and be ready for re-enable.
+	 */
+	if (wait_for((I915_READ(EDP_PSR_STATUS_CTL(dev)) &
+		      EDP_PSR_STATUS_STATE_MASK) == 0, 24)) {
+		DRM_ERROR("Timed out waiting for PSR Idle for re-enable\n");
+		return;
+	}
+
 	/* Enable/Re-enable PSR on the host */
 	intel_edp_psr_enable_source(intel_dp);
 
-- 
1.9.3