Re: [PATCH 11/18] drm/i915: switch to default context on idle

[Ben Widawsky <ben@bwidawsk.net>]

On Thu, 29 Mar 2012 21:29:05 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Sun, Mar 18, 2012 at 01:39:51PM -0700, Ben Widawsky wrote:
> > To keep things as sane as possible, switch to the default context before
> > idling. This should help free context objects, as well as put things in
> > a more well defined state before suspending.
> > 
> > Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> 
> Context are yet another thing that will nicely fragment our global gtt
> space. You don't pin them to mappable, which is a start, but I wonder
> whether we should integrate this into our evict_something code? Although
> that project is more involved with the current evict code, so maybe just
> add a fixme.
> 
> > ---
> >  drivers/gpu/drm/i915/i915_gem.c |    6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index 0985aa5..c1aab45 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -3685,6 +3685,8 @@ int
> >  i915_gem_idle(struct drm_device *dev)
> >  {
> >  	drm_i915_private_t *dev_priv = dev->dev_private;
> > +	struct intel_ring_buffer *ring = &dev_priv->ring[RCS];
> > +	u32 seqno;
> >  	int ret;
> >  
> >  	mutex_lock(&dev->struct_mutex);
> > @@ -3694,6 +3696,10 @@ i915_gem_idle(struct drm_device *dev)
> >  		return 0;
> >  	}
> >  
> > +	seqno = i915_gem_next_request_seqno(ring);
> > +	i915_switch_context(ring, NULL, DEFAULT_CONTEXT_ID, seqno, 0);
> > +	WARN_ON(i915_wait_request(ring, seqno, false));
> 
> This can block and potentially return early due to a signal, i.e. you need
> to properly handle this (like the i915_gpu_idle below).

Can you elaborate? Whether or not the context switch fails, I want to
try to idle the GPU. So I *thought* this is doing just that.

> 
> > +
> >  	ret = i915_gpu_idle(dev, true);
> >  	if (ret) {
> >  		mutex_unlock(&dev->struct_mutex);
> > -- 
> > 1.7.9.4
> > 
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>