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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 <rodrigo.vivi@intel.com> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20171005213842.11423-2-paulo.r.zanoni@intel.com
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@ -1220,6 +1220,9 @@ static int cnl_calc_wrpll_link(struct drm_i915_private *dev_priv,
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dco_freq += (((cfgcr0 & DPLL_CFGCR0_DCO_FRACTION_MASK) >>
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DPLL_CFGCR0_DCO_FRACTION_SHIFT) * ref_clock) / 0x8000;
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if (WARN_ON(p0 == 0 || p1 == 0 || p2 == 0))
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return 0;
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return dco_freq / (p0 * p1 * p2 * 5);
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}
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