drm/i915: Error out if we are trying to use VGA with SPLL already in use

Our static analysis tool noticed that 'reg' could be used uninitialized if
we are trying to get a PLL to drive VGA and SPLL is already in use
(plls->spll_refcoung != 0).

In the (error) case above, let's return false to the caller and emit an
error.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index bfcc58ffecbb2f7df4c9779d31455685ca452631..ebe52937246406bb12dd4a3e47dcf43d74acc385 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -898,6 +898,9 @@ bool intel_ddi_pll_mode_set(struct drm_crtc *crtc, int clock)
                        plls->spll_refcount++;
                        reg = SPLL_CTL;
                        intel_crtc->ddi_pll_sel = PORT_CLK_SEL_SPLL;
+               } else {
+                       DRM_ERROR("SPLL already in use\n");
+                       return false;
                }
 
                WARN(I915_READ(reg) & SPLL_PLL_ENABLE,