| Message ID | 20171005213842.11423-2-paulo.r.zanoni@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Oct 05, 2017 at 09:38:42PM +0000, Paulo Zanoni wrote: > 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. Good idea Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com> > --- > drivers/gpu/drm/i915/intel_ddi.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c > index f7c91bb..be86eb6 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); > } > > -- > 2.9.5 >
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c index f7c91bb..be86eb6 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); }
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> --- drivers/gpu/drm/i915/intel_ddi.c | 3 +++ 1 file changed, 3 insertions(+)