On Wed, 2014-04-16 at 10:41 +0800, Zhao Yakui wrote:
> 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.
>
> 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.
>
> V2->V3: Follow Daniel's comment to use the struct_mutext instead of
> atomic_t during determining which ring can be used to dispatch Video command.
>
> Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_dma.c | 3 +++
> drivers/gpu/drm/i915/i915_drv.h | 3 +++
> drivers/gpu/drm/i915/i915_gem_execbuffer.c | 40 +++++++++++++++++++++++++++-
> 3 files changed, 45 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 0b38f88..f7558f5 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);
> + dev_priv->ring_index = 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 74aef6a..032f992 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1472,6 +1472,8 @@ struct drm_i915_private {
> struct i915_dri1_state dri1;
> /* Old ums support infrastructure, same warning applies. */
> struct i915_ums_state ums;
> + /* the indicator for dispatch video commands on two BSD rings */
> + int ring_index;
> };
>
> static inline struct drm_i915_private *to_i915(const struct drm_device *dev)
> @@ -1679,6 +1681,7 @@ 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..1dc6f03 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -999,6 +999,37 @@ 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 ring_id;
> +
> + mutex_lock(&dev->struct_mutex);
> + if (dev_priv->ring_index == 0) {
> + ring_id = VCS;
> + dev_priv->ring_index = 1;
> + } else {
> + ring_id = VCS2;
> + dev_priv->ring_index = 0;
> + }
> + file_priv->bsd_ring = &dev_priv->ring[ring_id];
> + mutex_unlock(&dev->struct_mutex);
> + return ring_id;
> + }
> +}
> +
> static int
> i915_gem_do_execbuffer(struct drm_device *dev, void *data,
> struct drm_file *file,
> @@ -1043,7 +1074,14 @@ 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)) {
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