[Intel-gfx] [PATCH] drm/i915: Disable DC5 before going to DC9

[Rodrigo Vivi]

According to BSPec:
	Sequence to Allow DC9:
		1. Follow Sequence to Disallow DC5.

which is:
	Sequence to Disallow DC5 and DC6
		Set DC_STATE_EN Dynamic DC State Enable = "Disable".

I understand that we haven't had any issue so far. But since
DC9 is a software thing, it is better to disable DC5 before
to avoid any conflict. And respect the spec to avoid potential
future issues.

Cc: Imre Deak <imre.deak at intel.com>
Cc: Anshuman Gupta <anshuman.gupta at intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa at intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display_power.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
index 6a5695008f7c..b3cf5182044f 100644
--- a/drivers/gpu/drm/i915/display/intel_display_power.c
+++ b/drivers/gpu/drm/i915/display/intel_display_power.c
@@ -883,6 +883,9 @@ static void bxt_enable_dc9(struct drm_i915_private *dev_priv)
 {
 	assert_can_enable_dc9(dev_priv);
 
+	/* Disable DC5 before enabling DC9 */
+	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
+
 	drm_dbg_kms(&dev_priv->drm, "Enabling DC9\n");
 	/*
 	 * Power sequencer reset is not needed on
-- 
2.34.1