[Intel-gfx] [PATCH 03/14] drm/i915: Power down the DSI PLL before reconfiguring it

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

The BIOS may leave the DSI PLL enabled in some wonky state where it just
refuses to lock. Simply disabling the PLL before reconfiguring it is not
enough to fix it, but power gating the PLL prior to reconfiguring does
work.

This happens on BYT FFRD8 when booting with HDMI connected so the DSI
display will not be lit up by the BIOS.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dsi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index 781c267..8c9f1c5 100644
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -915,6 +915,11 @@ static void intel_dsi_pre_pll_enable(struct intel_encoder *encoder)
 
 	intel_dsi_prepare(encoder);
 
+	/*
+	 * The BIOS may leave the PLL in a wonky state where it doesn't
+	 * lock. It needs to be fully powered down to fix it.
+	 */
+	vlv_disable_dsi_pll(encoder);
 	vlv_enable_dsi_pll(encoder);
 }
 
-- 
2.4.6