Since we use a HW readback or estimation of the CS timestamp frequency,
sometimes it may result in 0. Avoid the division-by-zero in computing
its reciprocal, the timestamp period.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_device_info.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_device_info.c 
b/drivers/gpu/drm/i915/intel_device_info.c
index a97437fac884..18d9de488593 100644
--- a/drivers/gpu/drm/i915/intel_device_info.c
+++ b/drivers/gpu/drm/i915/intel_device_info.c
@@ -1044,13 +1044,17 @@ void intel_device_info_runtime_init(struct 
drm_i915_private *dev_priv)
        }
 
        /* Initialize command stream timestamp frequency */
-       runtime->cs_timestamp_frequency_khz = 
read_timestamp_frequency(dev_priv);
-       runtime->cs_timestamp_period_ns =
-               div_u64(1e6, runtime->cs_timestamp_frequency_khz);
-       drm_dbg(&dev_priv->drm,
-               "CS timestamp wraparound in %lldms\n",
-               div_u64(mul_u32_u32(runtime->cs_timestamp_period_ns, S32_MAX),
-                       USEC_PER_SEC));
+       runtime->cs_timestamp_frequency_khz =
+               read_timestamp_frequency(dev_priv);
+       if (runtime->cs_timestamp_frequency_khz) {
+               runtime->cs_timestamp_period_ns =
+                       div_u64(1e6, runtime->cs_timestamp_frequency_khz);
+               drm_dbg(&dev_priv->drm,
+                       "CS timestamp wraparound in %lldms\n",
+                       div_u64(mul_u32_u32(runtime->cs_timestamp_period_ns,
+                                           S32_MAX),
+                               USEC_PER_SEC));
+       }
 }
 
 void intel_driver_caps_print(const struct intel_driver_caps *caps,
-- 
2.25.0

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