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Geminilake requires the 3D driver to select whether barriers are intended for compute shaders, or tessellation control shaders, by whacking a "Barrier Mode" bit in SLICE_COMMON_ECO_CHICKEN1 when switching pipelines. Failure to do this properly can result in GPU hangs. Unfortunately, this means it needs to switch mid-batch, so only userspace can properly set it. To facilitate this, the kernel needs to whitelist the register. The workarounds page currently tags this as applying to Broxton only, but that doesn't make sense. The documentation for the register it references says the bit userspace is supposed to toggle only exists on Geminilake. Empirically, the Mesa patch to toggle this bit appears to fix intermittent GPU hangs in tessellation control shader barrier tests on Geminilake; we haven't seen those hangs on Broxton. v2: Mention WA #0862 in the comment (it doesn't have a name). Signed-off-by: Kenneth Graunke <kenneth@whitecape.org> Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: stable@vger.kernel.org Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180105085905.9298-1-kenneth@whitecape.org (cherry picked from commit ab062639edb0412daf6de540725276b9a5d217f9) Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.