drm/i915: HSW/BDW PSR Set idle_frames = VBT + 1

Let's use VBT + 1 now we parse it.

v2: fix subject

v3: rebase over intel_psr and without counting on previous fix

Cc: Arthur Runyan <arthur.j.runyan@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_psr.c

@@ -163,7 +163,12 @@ static void intel_psr_enable_source(struct intel_dp *intel_dp)
 	struct drm_device *dev = dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	uint32_t max_sleep_time = 0x1f;
-	uint32_t idle_frames = 1;
+	/* Lately it was identified that depending on panel idle frame count
+	 * calculated at HW can be off by 1. So let's use what came
+	 * from VBT + 1 and at minimum 2 to be on the safe side.
+	 */
+	uint32_t idle_frames = dev_priv->vbt.psr.idle_frames ?
+			       dev_priv->vbt.psr.idle_frames + 1 : 2;
 	uint32_t val = 0x0;
 	const uint32_t link_entry_time = EDP_PSR_MIN_LINK_ENTRY_TIME_8_LINES;
 	bool only_standby = false;