From: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date: Tue, 24 Sep 2013 18:26:21 +0000 (+0300)
Subject: drm/i915: Don't underflow bestppm
X-Git-Tag: v3.13-rc1~76^2~68^2~126
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c686122c638838ce7113aeb22e4f1c50446de6eb;p=thirdparty%2Fkernel%2Flinux.git

drm/i915: Don't underflow bestppm

We do 'bestppm - 10' in vlv_find_best_dpll() but never check whether
that might underflow. Add such a check.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
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 dc5077560c740..789e6ab8fb19c 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -708,7 +708,7 @@ vlv_find_best_dpll(const intel_limit_t *limit, struct drm_crtc *crtc,
 						bestppm = 0;
 						flag = 1;
 					}
-					if (ppm < bestppm - 10) {
+					if (bestppm >= 10 && ppm < bestppm - 10) {
 						bestppm = ppm;
 						flag = 1;
 					}