Re: [PATCH 0/5] drm/i915: Add the support of dual BSD rings on BDW GT3

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Apr 09, 2014 at 09:59:51AM +0800, Zhao Yakui wrote:
> 
> This is the patch set that tries to add the support of dual BSD rings on BDW
> GT3. Based on hardware spec, the BDW GT3 has two independent BSD rings, which
> can be used to process the video commands. To be simpler, it is transparent 
> to user-space driver/middleware. In such case the kernel driver will decide
> which ring is to dispatch the BSD video command.
> 
> As every BSD ring is powerful, it is enough to dispatch the BSD video command
> based on the drm fd. In such case the different BSD ring is used for video playing
> back and encoding. At the same time the coarse dispatch mechanism can help to avoid
> the object synchronization between the BSD rings.

Ok, I've quickly read through it all and commented on a few things. Imo
the last patch should be massively simplified, at least for the first
round. Other things look small.

What's still missing are testcases, and I have two things in mind here:
- Exercise the 2nd ring dispatch and sync a bit. Since the 2nd bsd ring is
  hidden within the kernel I think the right approach would be to open a
  few drm fds (10 or so) and then randomly use them with a dummy reloc. We
  have two testcases which can be used as blueprints that need
  adjustement:

  - gem_ring_sync_loop: Probably easiest to copy it to a new file as
    gem_multi_bsd_sync_loop. This test exercises semaphores.
  - gem_dummy_reloc_loop, subtest mixed: Almost the same as the above, but
    the sync is done _inside_ the loop and hence this exercises gpu/cpu
    sync. We need both tests adjusted, for for this we need a new
    multi-bsd test.

- New testcase to fully test main execbuffer flags. This is simply
  something that's we don't yet have. The next guy to touch execbuf code
  needs to add it, and it looks like that's you ;-) I've done a JIRA task
  for the resource streamer work, but I think the resource streamer wont
  be merged anytime soon. So I'll reassign to you. Jira task is VIZ-3129.

Thanks, Daniel

> 
> 
> Zhao Yakui (5):
>   drm/i915: Split the BDW device definition to prepare for dual BSD
>     rings on BDW GT3
>   drm/i915: Initialize the second BSD ring on BDW GT3 machine
>   drm/i915: Handle the irq interrupt for the second BSD ring
>   drm/i915: Add the VCS2 switch in Intel_ring_setup_status_page for Gen7 to
>     remove the switch check warning
>   drm/i915: Use the coarse mechanism based on drm fd to dispatch the BSD command
>     on BDW GT3
> 
>  drivers/gpu/drm/i915/i915_dma.c            |   14 ++++++
>  drivers/gpu/drm/i915/i915_drv.c            |   24 ++++++++-
>  drivers/gpu/drm/i915/i915_drv.h            |    5 ++
>  drivers/gpu/drm/i915/i915_gem.c            |    9 +++-
>  drivers/gpu/drm/i915/i915_gem_execbuffer.c |   73 +++++++++++++++++++++++++++-
>  drivers/gpu/drm/i915/i915_gpu_error.c      |    1 +
>  drivers/gpu/drm/i915/i915_irq.c            |    5 +-
>  drivers/gpu/drm/i915/i915_reg.h            |    1 +
>  drivers/gpu/drm/i915/intel_ringbuffer.c    |   57 ++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_ringbuffer.h    |    6 ++-
>  include/drm/i915_pciids.h                  |   10 ++--
>  11 files changed, 197 insertions(+), 8 deletions(-)
> 
> -- 
> 1.7.10.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch