[Intel-gfx] [PATCH v3 21/21] drm/i915: Unify GPU resets upon shutdown

[Chris Wilson]

On Mon, Apr 25, 2016 at 08:25:14PM +0300, Ville Syrjälä wrote:
> On Sun, Apr 24, 2016 at 07:10:19PM +0100, Chris Wilson wrote:
> > Both execlists and legacy need to reset the context (and mode) of the
> > GPU before we lose control of the system. By resetting the GPU, we
> > revert back to default settings. This simplifies the life of any
> > subsequent driver (in particular for virtualized setups) as it does not
> > then have to try and recover from an unknown condition. As both paths
> > need to reset for the same reason, move the reset to a common point.
> > 
> > This unifies the resets added in a647828afc (drm/i915: Also perform gpu
> > reset under execlist mode) and 8e96d9c4d9 (drm/i915: reset the GPU on
> > context fini).
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> > CC: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala at intel.com>
> > Cc: "Niu, Bing" <bing.niu at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_dma.c         | 41 ++++++++++++++++++++++++++-------
> >  drivers/gpu/drm/i915/i915_gem.c         |  8 -------
> >  drivers/gpu/drm/i915/i915_gem_context.c |  8 +------
> >  3 files changed, 34 insertions(+), 23 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> > index 5c7615041b31..68c60f4fd44d 100644
> > --- a/drivers/gpu/drm/i915/i915_dma.c
> > +++ b/drivers/gpu/drm/i915/i915_dma.c
> > @@ -425,6 +425,37 @@ static const struct vga_switcheroo_client_ops i915_switcheroo_ops = {
> >  	.can_switch = i915_switcheroo_can_switch,
> >  };
> >  
> > +static void i915_gem_fini(struct drm_device *dev)
> > +{
> > +	int reset;
> > +
> > +	/*
> > +	 * Neither the BIOS, ourselves or any other kernel
> > +	 * expects the system to be in execlists mode on startup,
> > +	 * so we need to reset the GPU back to legacy mode. And the only
> > +	 * known way to disable logical contexts is through a GPU reset.
> > +	 *
> > +	 * So in order to leave the system in a known default configuration,
> > +	 * always reset the GPU upon unload. Afterwards we then clean up the
> > +	 * GEM state tracking, flushing off the requests and leaving the
> > +	 * system in a known idle state.
> > +	 *
> > +	 * Note that is of the upmost importance that the GPU is idle and
> > +	 * all stray writes are flushed *before* we dismantle the backing
> > +	 * storage for the pinned objects.
> > +	 */
> > +	reset = intel_gpu_reset(dev, ALL_ENGINES);
> 
> That's going to kill pre-g4x macines I think. At least until Maarten's
> reset locking fixes go in. Even then I'm not sure we want to do that on
> those old machines.

Reset locking in shutdown? intel_gpu_reset() is just the register poke.
We can limit it to say gen5 to be safe?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre