drm/i915: Avoid div-by-zero in clock calculation funcs

Check that the N and P dividers don't cause a divide by zero.

This shouldn't happen under normal circumstances, but can
happen eg. under simulation.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
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 0332d7ca892d59c0ae66b7e8df9f391058a6cc45..66b39dbaf12c91bcc4a457587fb253c172be98b5 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -329,6 +329,8 @@ static void vlv_clock(int refclk, intel_clock_t *clock)
 {
        clock->m = clock->m1 * clock->m2;
        clock->p = clock->p1 * clock->p2;
+       if (WARN_ON(clock->n == 0 || clock->p == 0))
+               return;
        clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n);
        clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p);
 }
@@ -430,6 +432,8 @@ static void pineview_clock(int refclk, intel_clock_t *clock)
 {
        clock->m = clock->m2 + 2;
        clock->p = clock->p1 * clock->p2;
+       if (WARN_ON(clock->n == 0 || clock->p == 0))
+               return;
        clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n);
        clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p);
 }
@@ -443,6 +447,8 @@ static void i9xx_clock(int refclk, intel_clock_t *clock)
 {
        clock->m = i9xx_dpll_compute_m(clock);
        clock->p = clock->p1 * clock->p2;
+       if (WARN_ON(clock->n + 2 == 0 || clock->p == 0))
+               return;
        clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n + 2);
        clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p);
 }