The driver doesn't seem to report the actual value.
I have sent the patch to fix this: https://patchwork.freedesktop.org/patch/230063/
commit 25ec806eb249603ad0364365ab620628cf25f031 Author: Danylo Piliaiev <danylo.piliaiev@gmail.com> Date: Mon Jun 18 15:50:57 2018 +0300 i965: Advertise 8 bits subpixel precision for viewport bounds on gen6+ We use floating-points for viewport bounds so VIEWPORT_SUBPIXEL_BITS should reflect this. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105975 Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com> Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
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