drm/i915: Convert BUG_ON(!pll->active) and friends to a WARN

Turn a fatal lockup into a merely blank display with lots of shouty
messages.

v2: Whilst in the area, convert the other BUG_ON into less fatal errors.
In particular, note that we may be called on a PCH platform not using
PLLs, such as Haswell, and so we do not always want to BUG_ON(!pll)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 956b22899b7172f72b377c64ed3e7b27ac05698e..9dc42bf557bed9f80b0d6adaff59a7ac6001c9d5 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1403,14 +1403,18 @@ out_unlock:
 static void intel_enable_pch_pll(struct intel_crtc *intel_crtc)
 {
        struct drm_i915_private *dev_priv = intel_crtc->base.dev->dev_private;
-       struct intel_pch_pll *pll = intel_crtc->pch_pll;
+       struct intel_pch_pll *pll;
        int reg;
        u32 val;
 
-       /* PCH only available on ILK+ */
+       /* PCH PLLs only available on ILK, SNB and IVB */
        BUG_ON(dev_priv->info->gen < 5);
-       BUG_ON(pll == NULL);
-       BUG_ON(pll->refcount == 0);
+       pll = intel_crtc->pch_pll;
+       if (pll == NULL)
+               return;
+
+       if (WARN_ON(pll->refcount == 0))
+               return;
 
        DRM_DEBUG_KMS("enable PCH PLL %x (active %d, on? %d)for crtc %d\n",
                      pll->pll_reg, pll->active, pll->on,
@@ -1448,13 +1452,18 @@ static void intel_disable_pch_pll(struct intel_crtc *intel_crtc)
        if (pll == NULL)
               return;
 
-       BUG_ON(pll->refcount == 0);
+       if (WARN_ON(pll->refcount == 0))
+               return;
 
        DRM_DEBUG_KMS("disable PCH PLL %x (active %d, on? %d) for crtc %d\n",
                      pll->pll_reg, pll->active, pll->on,
                      intel_crtc->base.base.id);
 
-       BUG_ON(pll->active == 0);
+       if (WARN_ON(pll->active == 0)) {
+               assert_pch_pll_disabled(dev_priv, intel_crtc);
+               return;
+       }
+
        if (--pll->active) {
                assert_pch_pll_enabled(dev_priv, intel_crtc);
                return;