On Fri, Feb 24, 2017 at 11:47:56AM +0200, Mika Kuoppala wrote:
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
>
> > We are required to reload the TLBs around ppgtt switches. However, we
> > already do an unconditional TLB invalidate before every batch and a flush
> > afterwards, so this condition is already satisfied without extra flushes
> > around the LRI instructions.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_gem_gtt.c | 17 -----------------
> > 1 file changed, 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index 057239ab3f70..999f15455f48 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -1431,13 +1431,8 @@ static int hsw_mm_switch(struct i915_hw_ppgtt *ppgtt,
> > {
> > struct intel_engine_cs *engine = req->engine;
> > u32 *cs;
> > - int ret;
> >
> > /* NB: TLBs must be flushed and invalidated before a switch */
> > - ret = engine->emit_flush(req, EMIT_INVALIDATE | EMIT_FLUSH);
>
> The pattern slightly changes as you dont get the flush on the first
> switch.
>
> But what is there to flush on first switch anyways.
Those flushes onto the empty ring have always left me questioning my
sanity ;)
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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