[Intel-gfx] [PATCH 01/18] drm/i915: Comments for semaphore clarification
Ben Widawsky
ben at bwidawsk.net
Tue May 7 18:51:16 CEST 2013
On Tue, May 07, 2013 at 02:54:06PM +0100, Damien Lespiau wrote:
> On Sat, Apr 27, 2013 at 05:59:12PM -0700, Ben Widawsky wrote:
> > Semaphores are tied very closely to the rings in the GPU. Trivial patch
> > adds comments to the existing code so that when we add new rings we can
> > include comments there as well. It also helps distinguish the ring to
> > semaphore mailbox interactions by using the ringname in the semaphore
> > data structures.
> >
> > This patch should have no functional impact.
> >
> > A subset of this patch was:
> > Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> > ---
> > drivers/gpu/drm/i915/i915_reg.h | 12 ++++++------
> > drivers/gpu/drm/i915/intel_ringbuffer.c | 18 +++++++++---------
> > drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +-
> > 3 files changed, 16 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 4d66898..767aa32 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -267,12 +267,12 @@
> > #define MI_SEMAPHORE_UPDATE (1<<21)
> > #define MI_SEMAPHORE_COMPARE (1<<20)
> > #define MI_SEMAPHORE_REGISTER (1<<18)
> > -#define MI_SEMAPHORE_SYNC_RV (2<<16)
> > -#define MI_SEMAPHORE_SYNC_RB (0<<16)
> > -#define MI_SEMAPHORE_SYNC_VR (0<<16)
> > -#define MI_SEMAPHORE_SYNC_VB (2<<16)
> > -#define MI_SEMAPHORE_SYNC_BR (2<<16)
> > -#define MI_SEMAPHORE_SYNC_BV (0<<16)
> > +#define MI_SEMAPHORE_SYNC_RB (0<<16) /* RCS wait for BCS (BRSYNC) */
> > +#define MI_SEMAPHORE_SYNC_RV (2<<16) /* RCS wait for VCS (VRSYNC) */
> > +#define MI_SEMAPHORE_SYNC_VR (0<<16) /* VCS wait for RCS (RVSYNC) */
> > +#define MI_SEMAPHORE_SYNC_VB (2<<16) /* VCS wait for BCS (BVSYNC) */
> > +#define MI_SEMAPHORE_SYNC_BV (0<<16) /* BCS wait for VCS (VBSYNC) */
> > +#define MI_SEMAPHORE_SYNC_BR (2<<16) /* BCS wait for RCS (RBSYNC) */
>
> Huum aren't the register names inverted in the comment? RCS waiting for
> BCS would be RBSYNC? (Register read by RCS, written by BCS)
>
> --
> Damien
Admittedly this code is quite confusing. So I won't go past, I *think*
The current comments are correct.
Using the example of the render waiting on the blitter:
gen6_ring_sync(render, blitter, seqno)
iender emits a wait on:
blitter->semaphore_register[RCS] (MI_SEMAPHORE_SYNC_BR)
gen6_add_request(blitter)
update_mboxes(GEN6_RBSYNC)
update_mboxes(GEN6_VBSYNC)
So in this case:
MI_SEMAPHORE_SYNC_BR <==> GEN6_RBSYNC
>
> > #define MI_SEMAPHORE_SYNC_INVALID (1<<0)
> > /*
> > * 3D instructions used by the kernel
> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > index 1d5d613..38751a7 100644
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > @@ -1666,9 +1666,9 @@ int intel_init_render_ring_buffer(struct drm_device *dev)
> > ring->get_seqno = gen6_ring_get_seqno;
> > ring->set_seqno = ring_set_seqno;
> > ring->sync_to = gen6_ring_sync;
> > - ring->semaphore_register[0] = MI_SEMAPHORE_SYNC_INVALID;
> > - ring->semaphore_register[1] = MI_SEMAPHORE_SYNC_RV;
> > - ring->semaphore_register[2] = MI_SEMAPHORE_SYNC_RB;
> > + ring->semaphore_register[RCS] = MI_SEMAPHORE_SYNC_INVALID;
> > + ring->semaphore_register[VCS] = MI_SEMAPHORE_SYNC_RV;
> > + ring->semaphore_register[BCS] = MI_SEMAPHORE_SYNC_RB;
> > ring->signal_mbox[0] = GEN6_VRSYNC;
> > ring->signal_mbox[1] = GEN6_BRSYNC;
> > } else if (IS_GEN5(dev)) {
> > @@ -1825,9 +1825,9 @@ int intel_init_bsd_ring_buffer(struct drm_device *dev)
> > ring->irq_put = gen6_ring_put_irq;
> > ring->dispatch_execbuffer = gen6_ring_dispatch_execbuffer;
> > ring->sync_to = gen6_ring_sync;
> > - ring->semaphore_register[0] = MI_SEMAPHORE_SYNC_VR;
> > - ring->semaphore_register[1] = MI_SEMAPHORE_SYNC_INVALID;
> > - ring->semaphore_register[2] = MI_SEMAPHORE_SYNC_VB;
> > + ring->semaphore_register[RCS] = MI_SEMAPHORE_SYNC_VR;
> > + ring->semaphore_register[VCS] = MI_SEMAPHORE_SYNC_INVALID;
> > + ring->semaphore_register[BCS] = MI_SEMAPHORE_SYNC_VB;
> > ring->signal_mbox[0] = GEN6_RVSYNC;
> > ring->signal_mbox[1] = GEN6_BVSYNC;
> > } else {
> > @@ -1871,9 +1871,9 @@ int intel_init_blt_ring_buffer(struct drm_device *dev)
> > ring->irq_put = gen6_ring_put_irq;
> > ring->dispatch_execbuffer = gen6_ring_dispatch_execbuffer;
> > ring->sync_to = gen6_ring_sync;
> > - ring->semaphore_register[0] = MI_SEMAPHORE_SYNC_BR;
> > - ring->semaphore_register[1] = MI_SEMAPHORE_SYNC_BV;
> > - ring->semaphore_register[2] = MI_SEMAPHORE_SYNC_INVALID;
> > + ring->semaphore_register[RCS] = MI_SEMAPHORE_SYNC_BR;
> > + ring->semaphore_register[VCS] = MI_SEMAPHORE_SYNC_BV;
> > + ring->semaphore_register[BCS] = MI_SEMAPHORE_SYNC_INVALID;
> > ring->signal_mbox[0] = GEN6_RBSYNC;
> > ring->signal_mbox[1] = GEN6_VBSYNC;
> > ring->init = init_ring_common;
> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> > index d66208c..785df13 100644
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> > @@ -102,7 +102,7 @@ struct intel_ring_buffer {
> > struct intel_ring_buffer *to,
> > u32 seqno);
> >
> > - u32 semaphore_register[3]; /*our mbox written by others */
> > + u32 semaphore_register[I915_NUM_RINGS]; /*our mbox written by others */
> > u32 signal_mbox[2]; /* mboxes this ring signals to */
> > /**
> > * List of objects currently involved in rendering from the
> > --
> > 1.8.2.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ben Widawsky, Intel Open Source Technology Center
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