RC6 residency should be in intervals of 1.28us, and the counter wraps.
Here is an example using awk to get the various RC6 and RC6+ residency
times in seconds, since boot.

cat /sys/kernel/debug/dri/0/i915_drpc_info  | grep residency | awk -F':' -F' '  '{print $5 * 1.28 / 1000000}'

This is primarily for QA, but has other applications as well. An
upcoming patch to add interfaces should be more interesting to
application developers.

v2: move comment to the correct place

v3: display with %u instead of %d, for Ouping

CC: Ouping Zhang <ouping.zhang@intel.com>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Ben Widawsky <benjamin.widawsky@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>