[Intel-gfx] [PATCH] drm/i915/display: Add missing checks for cdclk crawling

[Anusha Srivatsa <anusha.srivatsa@intel.com>]

cdclk_sanitize() function was written assuming vco was a signed integer.
vco gets assigned to -1 (essentially ~0) for the case where PLL
might be enabled and vco is not a frequency that will ever
get used. In such a scenario the right thing to do is disable the
PLL and re-enable it again with a valid frequency.
However the vco is declared as a unsigned variable.
With the above assumption, driver takes crawl path when not needed.
Add explicit check to not crawl in the case of an invalid PLL.

Cc: Matt Roper <matthew.d.roper@intel.com>
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
---
 drivers/gpu/drm/i915/display/intel_cdclk.c | 2 ++
 drivers/gpu/drm/i915/display/intel_cdclk.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
index 8a9031012d74..91112d266763 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -1962,6 +1962,8 @@ static bool intel_cdclk_can_crawl(struct drm_i915_private *dev_priv,
 	if (!HAS_CDCLK_CRAWL(dev_priv))
 		return false;
 
+	if (intel_pll_is_unknown(a->vco))
+		return false;
 	/*
 	 * The vco and cd2x divider will change independently
 	 * from each, so we disallow cd2x change when crawling.
diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.h b/drivers/gpu/drm/i915/display/intel_cdclk.h
index c674879a84a5..6eb83d806f11 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.h
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.h
@@ -80,6 +80,7 @@ intel_atomic_get_cdclk_state(struct intel_atomic_state *state);
 	to_intel_cdclk_state(intel_atomic_get_old_global_obj_state(state, &to_i915(state->base.dev)->display.cdclk.obj))
 #define intel_atomic_get_new_cdclk_state(state) \
 	to_intel_cdclk_state(intel_atomic_get_new_global_obj_state(state, &to_i915(state->base.dev)->display.cdclk.obj))
+#define intel_pll_is_unknown(vco)	((vco) == ~0)
 
 int intel_cdclk_init(struct drm_i915_private *dev_priv);
 
-- 
2.25.1