[Intel-gfx] [PATCH 13/13] DONT_MERGE drm/i915: FORCE_RESTORE for gen8 semaphores

[Chris Wilson]

On Tue, Apr 29, 2014 at 02:52:40PM -0700, Ben Widawsky wrote:
> This appears to not actually be needed on the current code. Just putting
> it on the ML so we can point bug reports at it later.
> 
> As pointed out by Ville, the current code is "broken" since we do
> FORCE_RESTORE, and RESTORE_INHIBIT on the same dword. Anecdotally, this
> seems fine.
> 
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_gem_context.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index f77b4c1..aa82fb4 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -661,6 +661,13 @@ static int do_switch(struct intel_ring_buffer *ring,
>  	if (!to->is_initialized || i915_gem_context_is_default(to))
>  		hw_flags |= MI_RESTORE_INHIBIT;
>  
> +	/* When SW intends to use semaphore signaling between Command streamers,
> +	 * it must avoid lite restores in HW by programming "Force Restore" bit
> +	 * to ‘1’ in context descriptor during context submission
> +	 */
> +	if (IS_GEN8(ring->dev) && i915_semaphore_is_enabled(ring->dev))
> +		hw_flags |= MI_FORCE_RESTORE;

Is it not an error to set both FORCE and INHIBIT?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre