drm/i915: PSR: Increase idle_frames

Idle frames the number of identical frames needed
before panel can enter PSR.

There are some panels that requires up to minimum of 4 idle
frames available on the market. For these cases usually
VBT should be used to configure the number of idle frames,
but unfortunately this isn't always true and VBT isn't being
set at all.

Let's trust VBT when it is set + 1  and use minimum of 4 + 1
when VBT isn't set. "+1" covers the "of-by-one" case.
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_psr.c

@@ -254,10 +254,13 @@ static void hsw_psr_enable_source(struct intel_dp *intel_dp)
 	uint32_t max_sleep_time = 0x1f;
 	/* 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.
+	 * from VBT + 1.
+	 * There are also other cases where panel demands at least 4
+	 * but VBT is not being set. To cover these 2 cases lets use
+	 * at least 5 when VBT isn't set to be on the safest side.
 	 */
 	uint32_t idle_frames = dev_priv->vbt.psr.idle_frames ?
-			       dev_priv->vbt.psr.idle_frames + 1 : 2;
+			       dev_priv->vbt.psr.idle_frames + 1 : 5;
 	uint32_t val = 0x0;
 	const uint32_t link_entry_time = EDP_PSR_MIN_LINK_ENTRY_TIME_8_LINES;