[Intel-gfx] [PATCH] Revert "drm/i915/psr: Make idle_frames sensible again"

[Rodrigo Vivi]

This reverts commit 1c80c25fb622973dd135878e98d172be20859049.

There are panels that needs 4 idle frames before entering PSR,
but VBT is unproperly set.

Also lately it was identified that idle frame count calculated at HW
can be off by 1, what makes the minimum of 2, at least.

Without the current vbt+1 we are with the risk of having HW calculating
0 idle frames and entering PSR when it shouldn't. Regardless the lack
of link training.

Cc: Dominik Brodowski <linux at dominikbrodowski.net>
Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Daniel Vetter <daniel.vetter at intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/intel_psr.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
index 59a21c9..108ba1e 100644
--- a/drivers/gpu/drm/i915/intel_psr.c
+++ b/drivers/gpu/drm/i915/intel_psr.c
@@ -255,14 +255,14 @@ static void hsw_psr_enable_source(struct intel_dp *intel_dp)
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
 	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.
-	 * 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.
+	/*
+	 * Let's respect VBT in case VBT asks a higher idle_frame value.
+	 * Let's use 6 as the minimum to cover all known cases including
+	 * the off-by-one issue that HW has in some cases. Also there are
+	 * cases where sink should be able to train
+	 * with the 5 or 6 idle patterns.
 	 */
-	uint32_t idle_frames = dev_priv->vbt.psr.idle_frames + 1;
+	uint32_t idle_frames = max(6, dev_priv->vbt.psr.idle_frames);
 	uint32_t val = EDP_PSR_ENABLE;
 
 	val |= max_sleep_time << EDP_PSR_MAX_SLEEP_TIME_SHIFT;
-- 
1.9.1