[PATCH] drm/i915: Fix DPLL warning when starting guest VM

[Zhao, Xinda]

The warning is occurred in guest VM when trying to get clock in encoder
initialization.

intel_modeset_init()
  ->intel_modeset_setup_hw_state()
    ->intel_ddi_get_config()
      ->intel_ddi_clock_get()
        ->skl_ddi_clock_get()
          ->intel_get_shared_dpll_id()
            ->WARN_ON(pll < dev_priv->shared_dplls||
                pll > &dev_priv->shared_dplls[dev_priv->num_shared_dpll])

In encoder initialization, shared DPLL is used for calculating clock for
DDI ports, but it is not set when crtc is not active.
In some cases, encoder is enabled while crtc is disabled, during encoder
initialization, the warning occurred.

Signed-off-by: Zhao, Xinda <xinda.zhao at intel.com>
---
 drivers/gpu/drm/i915/intel_ddi.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 28c25cb..ef35c12 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1489,6 +1489,16 @@ void intel_ddi_clock_get(struct intel_encoder *encoder,
 			 struct intel_crtc_state *pipe_config)
 {
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct intel_crtc *crtc = to_intel_crtc(pipe_config->base.crtc);
+
+	/*
+	 * For DDI ports we always use a shared PLL.
+	 * But the shared PLL will not be set when crtc is not active.
+	 */
+	if (crtc->active == false) {
+		DRM_DEBUG_KMS("Trying to get clock, but pipe is not active.\n");
+		return;
+	}
 
 	if (INTEL_GEN(dev_priv) <= 8)
 		hsw_ddi_clock_get(encoder, pipe_config);
-- 
2.7.4