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

[Ben Widawsky]

On Wed, Apr 30, 2014 at 08:13:25AM +0100, Chris Wilson wrote:
> 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

Read the commit message.


-- 
Ben Widawsky, Intel Open Source Technology Center