[Intel-gfx] [PATCH] drm/i915: Specify bsd rings through exec flag

[Chris Wilson]

On Tue, Aug 05, 2014 at 03:54:04PM +0800, Zhipeng Gong wrote:
> On Broadwell GT3 we have 2 Video Command Streamers (VCS), but userspace
> has no control when using VCS1 or VCS2. This patch introduces a mechanism
> to avoid the default ping-pong mode and use one specific ring through
> execution flag.
> 
> Signed-off-by: Zhipeng Gong <zhipeng.gong at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_execbuffer.c | 19 +++++++++++++++++--
>  include/uapi/drm/i915_drm.h                |  8 +++++++-
>  2 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 60998fc..f9ed8e0 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -1279,8 +1279,23 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>  	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];
> +
> +			switch (args->flags & I915_EXEC_BSD_MASK) {
> +			case I915_EXEC_BSD_DEFAULT:
> +				ring_id = gen8_dispatch_bsd_ring(dev, file);
> +				ring = &dev_priv->ring[ring_id];
> +				break;
> +			case I915_EXEC_BSD_RING1:
> +				ring = &dev_priv->ring[VCS];
> +				break;
> +			case I915_EXEC_BSD_RING2:
> +				ring = &dev_priv->ring[VCS2];
> +				break;
> +			default:
> +				DRM_DEBUG("execbuf with unknown bsd ring: %d\n",
> + 					  (int)(args->flags & I915_EXEC_BSD_MASK));
> +				return -EINVAL;
> +			}
>  		} else
>  			ring = &dev_priv->ring[VCS];
>  	} else
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index ff57f07..421420a 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -736,7 +736,13 @@ struct drm_i915_gem_execbuffer2 {
>   */
>  #define I915_EXEC_HANDLE_LUT		(1<<12)
>  
> -#define __I915_EXEC_UNKNOWN_FLAGS -(I915_EXEC_HANDLE_LUT<<1)
> +/** Used for switching BSD rings on the platforms with two BSD rings */
> +#define I915_EXEC_BSD_MASK		(3<<13)
> +#define I915_EXEC_BSD_DEFAULT		(0<<13) /* default ping-pong mode */
> +#define I915_EXEC_BSD_RING1		(1<<13)
> +#define I915_EXEC_BSD_RING2		(2<<13)

There is room in the ring selection flags for expansion.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre