[Mesa-dev] [PATCH 0/6] Enable OpenGL 4.0 on Haswell

[Iago Toral Quiroga]

Enabling GL 4.0 in gen7 requires a bit of work because some hardware and kernel
combinations may not support all the features. Specifically, we need to know
if the kernel can do pipelined register writes. Unfortunately, this requires
that we emit batches at screen creation time when we don't have a brw_context
available (all our current batch emission infrastructure relies on this).
See [1] and [2] for more details.

This little series implements the minimum infrastructure necessary so we can
emit a batch to check for register writes at screen creation time.

The first 4 patches refactor some of the interl_batchbuffer code so they don't
require a brw_context parameter. This way we can reuse the code directly at
screen creation time.

There are still a few functions that we need but rely quite heavily on the
brw_context object, specifically, brw_emit_mi_flush() and
intel_batchbuffer_flush(). These need to access the brw_context mostly to
deal with things such as ring changes, flushing the batch when we exceed the
allocated buffer size, throttling, etc which we don't need in our particular
case, so we decided to have alternate implementation of these that are greatly
simplified for the case of checking register writes. Overall, the implementation
of these functions in brw_check_register_writes.c is ~50 SLOC, so it is really
not a lot of code and it skips a lot of the complexity that the more generic
batch buffer functions have to deal with all kinds of scenarios, so it seems
like an acceptable trade-off.

Patch 5 implements all this and also implements the check for the capacity to do
pipelined register writes using this new infrastructure. Basically, we create
our own batch buffer and the necessary objects to use it (buffer manager,
hardware context, etc), we then emit the register writes, check the result and
dispose of the all the objects after we're done.

Patch 6 simply calls this functionality when needed to see if we can expose
GL 4.0 on Haswell systems.

There are a number of other intel_batchbuffer functions that we don't need for
this particular case but that we could also modify to accept a batchbuffer
object instead of a brw_context. I would be happy to write follow-up patches
to do that if we are interested.

[1] https://lists.freedesktop.org/archives/mesa-dev/2016-October/133439.html
[2] https://lists.freedesktop.org/archives/mesa-dev/2016-October/133502.html

Iago Toral Quiroga (6):
  i965: Make intel_bachbuffer_reloc() take a batchbuffer argument
  i965: make intel_batchbuffer_emit_dword() take a batchbuffer as
    argument
  i965: make intel_batchbuffer_free() take a batchbuffer as argument
  i965: remove brw_context dependency from intel_batchbuffer_init()
  i965: check if we support pipelined register writes at screen creation
    time
  i965/gen7: Enable OpenGL 4.0 in Haswell when supported

 src/mesa/drivers/dri/i965/Makefile.sources         |   1 +
 .../drivers/dri/i965/brw_check_register_writes.c   | 212 +++++++++++++++++++++
 src/mesa/drivers/dri/i965/brw_context.c            |   4 +-
 src/mesa/drivers/dri/i965/brw_context.h            |   3 +
 src/mesa/drivers/dri/i965/genX_blorp_exec.c        |   4 +-
 src/mesa/drivers/dri/i965/intel_batchbuffer.c      |  81 ++++----
 src/mesa/drivers/dri/i965/intel_batchbuffer.h      |  41 ++--
 src/mesa/drivers/dri/i965/intel_extensions.c       |  78 +-------
 src/mesa/drivers/dri/i965/intel_screen.c           |  11 +-
 9 files changed, 298 insertions(+), 137 deletions(-)
 create mode 100644 src/mesa/drivers/dri/i965/brw_check_register_writes.c

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