On Mon, 2014-04-14 at 01:22 -0600, Daniel Vetter wrote:
> On Mon, Apr 14, 2014 at 12:21:44PM +0800, Zhao Yakui wrote:
> > V1->V2: Follow Daniel's comment and use the simple ping-pong mechanism.
> > This is only to add the support of dual BSD rings on BDW GT3 machine.
> > The further optimization will be considered in another patch set.
> >
> > 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/middle.
> > Instead 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 it can play back video stream while
> > encoding
> > another video stream. The coarse ping-pong mechanism is used to determine
> > which BSD ring is used to dispatch the BSD video command.
> >
> > Signed-off-by: Zhao Yakui <yakui.z...@intel.com>
> > ---
> > drivers/gpu/drm/i915/i915_dma.c | 3 +++
> > drivers/gpu/drm/i915/i915_drv.h | 3 +++
> > drivers/gpu/drm/i915/i915_gem_execbuffer.c | 37
> > +++++++++++++++++++++++++++-
> > 3 files changed, 42 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_dma.c
> > b/drivers/gpu/drm/i915/i915_dma.c
> > index 0b38f88..4d27cf4 100644
> > --- a/drivers/gpu/drm/i915/i915_dma.c
> > +++ b/drivers/gpu/drm/i915/i915_dma.c
> > @@ -1572,6 +1572,7 @@ int i915_driver_load(struct drm_device *dev, unsigned
> > long flags)
> > spin_lock_init(&dev_priv->backlight_lock);
> > spin_lock_init(&dev_priv->uncore.lock);
> > spin_lock_init(&dev_priv->mm.object_stat_lock);
> > + atomic_set(&dev_priv->bsd_cmd_counter, 0);
> > mutex_init(&dev_priv->dpio_lock);
> > mutex_init(&dev_priv->modeset_restore_lock);
> >
> > @@ -1929,6 +1930,8 @@ void i915_driver_postclose(struct drm_device *dev,
> > struct drm_file *file)
> > {
> > struct drm_i915_file_private *file_priv = file->driver_priv;
> >
> > + if (file_priv && file_priv->bsd_ring)
> > + file_priv->bsd_ring = NULL;
> > kfree(file_priv);
> > }
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > b/drivers/gpu/drm/i915/i915_drv.h
> > index ac5598c3..68e8166 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -1466,6 +1466,8 @@ struct drm_i915_private {
> > struct i915_dri1_state dri1;
> > /* Old ums support infrastructure, same warning applies. */
> > struct i915_ums_state ums;
> > + /* the lock for dispatch video commands on two BSD rings */
> > + atomic_t bsd_cmd_counter;
>
> You're still using atomic_t for no real good reason.
> gen8_dispatch_bsd_ring is always called with the dev->struct_mutex lock
> held, so there's really no reason for it.
If the struct_mutex is used in the gen8_dispatch_bsd_ring, I can remove
the atomic_t.
It seems that the struct_mutex is a big lock and it is used very
frequently(i915_gem.c, i915_dma.c and so on). In my point it is a little
heavier than the atomic_t if one counter is increased and returned.
If you think that the mutex is better than atomic, I will follow your
advice.
Thanks.
Yakui
> -Daniel
>
> > };
> >
> > static inline struct drm_i915_private *to_i915(const struct drm_device
> > *dev)
> > @@ -1673,6 +1675,7 @@ struct drm_i915_file_private {
> >
> > struct i915_hw_context *private_default_ctx;
> > atomic_t rps_wait_boost;
> > + struct intel_ring_buffer *bsd_ring;
> > };
> >
> > /*
> > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > index 341ec68..720ef17 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > @@ -999,6 +999,34 @@ i915_reset_gen7_sol_offsets(struct drm_device *dev,
> > return 0;
> > }
> >
> > +/**
> > + * Find one BSD ring to dispatch the corresponding BSD command.
> > + * The Ring ID is returned.
> > + */
> > +static int gen8_dispatch_bsd_ring(struct drm_device *dev,
> > + struct drm_file *file)
> > +{
> > + struct drm_i915_private *dev_priv = dev->dev_private;
> > + struct drm_i915_file_private *file_priv = file->driver_priv;
> > +
> > + /* Check whether the file_priv is using one ring */
> > + if (file_priv->bsd_ring)
> > + return file_priv->bsd_ring->id;
> > + else {
> > + /* If no, use the ping-pong mechanism to select one ring */
> > + int counter, ring_id;
> > + smp_mb__before_atomic_inc();
> > + counter = atomic_inc_return(&dev_priv->bsd_cmd_counter);
> > + if (counter % 2 == 0)
> > + ring_id = VCS;
> > + else
> > + ring_id = VCS2;
> > +
> > + file_priv->bsd_ring = &dev_priv->ring[ring_id];
> > + return ring_id;
> > + }
> > +}
> > +
> > static int
> > i915_gem_do_execbuffer(struct drm_device *dev, void *data,
> > struct drm_file *file,
> > @@ -1043,7 +1071,14 @@ i915_gem_do_execbuffer(struct drm_device *dev, void
> > *data,
> >
> > if ((args->flags & I915_EXEC_RING_MASK) == I915_EXEC_DEFAULT)
> > ring = &dev_priv->ring[RCS];
> > - else
> > + else if ((args->flags & I915_EXEC_RING_MASK) == I915_EXEC_BSD) {
> > + if (HAS_BSD2(dev)) {
> > + int ring_id;
> > + ring_id = gen8_dispatch_bsd_ring(dev, file);
> > + ring = &dev_priv->ring[ring_id];
> > + } else
> > + ring = &dev_priv->ring[VCS];
> > + } else
> > ring = &dev_priv->ring[(args->flags & I915_EXEC_RING_MASK) - 1];
> >
> > if (!intel_ring_initialized(ring)) {
> > --
> > 1.7.10.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
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