drm/i915/gen9: Add 2us read latency to WM level
drm/i915/gen9: Add 2us read latency to WM level

According to the updated Bspec, The mailbox response data is not currently
accounting for memory read latency. Add 2 microseconds to the result for
each level.
This patch adds 2us to latency of level 0 for all cases and
for all other levels (1-7) only if latency[level] > 0.

v2: Slightly rework the patch and add a big comment (Damien)
v3: Rebase on top of the renames of the memory latency defines

Signed-off-by: Vandana Kannan <dd1566850b3aa5eb50ae774853f73d1deea1592d@intel.com> (v1)
Signed-off-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>
Reviewed-by: Ville Syrjälä <cd6e8d405ca90be3a03d5427c5b24fbd2d68dcc4@linux.intel.com> (v2)
Reviewed-by: M, Satheeshakrishna <45f4b2d98930289a5a5e29e08391044407e94a99@intel.com> (v1)
Cc: Lespiau, Damien <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>
Cc: M, Satheeshakrishna <45f4b2d98930289a5a5e29e08391044407e94a99@intel.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs