Prior to Skylake the Gen HW timestamps were driven by a 12.5MHz clock
with the convenient property of being able to scale by an integer (80)
to nanosecond units.
For Skylake the frequency is 12MHz or a scale factor of 83.333333
This updates gen_device_info to track a floating point timebase_scale
factor and makes corresponding _queryobj.c changes to no longer assume a
scale factor of 80 works across all gens.
Although the gen6_ code could have been been left alone, the changes
keep the code more comparable, and it now shares a few utility functions
for scaling raw timestamps and calculating deltas. The utility for
calculating deltas takes into account 32 or 36bit overflow depending on
the current kernel version.
Note: this leaves the timestamp handling of ARB_query_buffer_object
untouched, which continues to use an incorrect scale of 80 on Skylake
for now. This is more awkward to solve since the scaling is currently
done using a very limited uint64 ALU available to the command parser
that doesn't support multiply or divide where it's already taking a
large number of instructions just to effectively multiple by 80.
This fixes piglit arb_timer_query-timestamp-get on Skylake
v2: (Ken) Update timebase_scale for platforms past Skylake/Broxton too.
Signed-off-by: Robert Bragg <robert@sixbynine.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Robert Bragg
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