From: Paulo Zanoni Date: Thu, 5 Oct 2017 21:38:42 +0000 (-0300) Subject: drm/i915: avoid division by zero on cnl_calc_wrpll_link X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=0e005888b833;p=openwrt%2Fstaging%2Fblogic.git drm/i915: avoid division by zero on cnl_calc_wrpll_link If for some unexpected reason the registers all read zero it's better to WARN and return instead of dividing by zero and completely freezing the machine. I don't expect this to happen in the wild with the current code, but I accidentally triggered the division by zero while doing some debugging in an unusual environment. Cc: Rodrigo Vivi Signed-off-by: Paulo Zanoni Reviewed-by: Rodrigo Vivi Link: https://patchwork.freedesktop.org/patch/msgid/20171005213842.11423-2-paulo.r.zanoni@intel.com --- diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c index ce4b7335a78a..b307b6fe1ce3 100644 --- a/drivers/gpu/drm/i915/intel_ddi.c +++ b/drivers/gpu/drm/i915/intel_ddi.c @@ -1220,6 +1220,9 @@ static int cnl_calc_wrpll_link(struct drm_i915_private *dev_priv, dco_freq += (((cfgcr0 & DPLL_CFGCR0_DCO_FRACTION_MASK) >> DPLL_CFGCR0_DCO_FRACTION_SHIFT) * ref_clock) / 0x8000; + if (WARN_ON(p0 == 0 || p1 == 0 || p2 == 0)) + return 0; + return dco_freq / (p0 * p1 * p2 * 5); }