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On 09/11/17 14:13, Lionel Landwerlin
wrote:
On 09/11/17 14:06, Lionel Landwerlin
wrote:
+ } else if (INTEL_GEN(dev_priv) <= 9) {
+ u32 ctc_reg = I915_READ(GEN8_CTC_MODE);
+ u64 freq = 0;
+
+ if ((ctc_reg & GEN8_CTC_SOURCE_PARAMETER_MASK) ==
GEN8_CTC_SOURCE_DIVIDE_LOGIC)
+ freq =
read_timestamp_frequency_from_divide(dev_priv);
+ else
+ freq = IS_GEN9_LP(dev_priv) ? 19200000 :
24000000;
+
+ /* Now figure out how the command stream's timestamp
register
+ * increments from this frequency (it might increment
only
+ * every few clock cycle).
+ */
+ freq >>= 3 - ((ctc_reg &
GEN8_CTC_SHIFT_PARAMETER_MASK) >>
+ GEN8_CTC_SHIFT_PARAMETER_SHIFT);
Gen8 documentation is indeed fuzzy. Are we getting 12.5mhz after
this shift as doc says it to have 80ns base.
Forgot to answer that point. Let me check this on BDW again.
But yes, the idea is that we should get 12.5MHz on BDW.
Okay, looks like that's wrong on my BDW system....
So this bit of right shift should probably only be applied to the
else case (i.e. gen9)
-
Lionel
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