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

[Rodrigo Vivi <rodrigo.vivi@intel.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).

v2: The 24ms above takes in account 16ms for refresh rate on 60Hz mode. However
on low frequency modes this can take longer. So let's use 50ms for safeness.

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

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
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..2e8c544 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 some time 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, 50)) {
+		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