Re: [PATCH 1/9] drm/i915: Flush logical context image out to memory upon suspend

Chris Wilson
2016-07-15T11:11:06Z

On Fri, Jul 15, 2016 at 01:41:33PM +0300, Mika Kuoppala wrote:
> Chris Wilson <chris@chris-wilson.co.uk> writes:
>
> > Before suspend, and especially before building the hibernation image, we
> > need to context image to be coherent in memory. To do this we require
> > that we perform a context switch to a disposable context (i.e. the
> > dev_priv->kernel_context) - when that switch is complete, all other
> > context images will be complete. This leaves the kernel_context image as
> > incomplete, but fortunately that is disposable and we can do a quick
> > fixup of the logical state after resuming.
> >
> > Testcase: igt/gem_exec_suspend # bsw
> > References: https://bugs.freedesktop.org/show_bug.cgi?id=96526
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/i915_drv.c | 4 +---
> > drivers/gpu/drm/i915/i915_drv.h | 1 +
> > drivers/gpu/drm/i915/i915_gem.c | 46 +++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 48 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > index 15440123e38d..c5b7b8e0678a 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -1590,9 +1590,7 @@ static int i915_drm_resume(struct drm_device *dev)
> >
> > intel_csr_ucode_resume(dev_priv);
> >
> > - mutex_lock(&dev->struct_mutex);
> > - i915_gem_restore_gtt_mappings(dev);
> > - mutex_unlock(&dev->struct_mutex);
> > + i915_gem_resume(dev);
> >
> > i915_restore_state(dev);
> > intel_opregion_setup(dev_priv);
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 1ec523d29789..e73c0fc84c73 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -3384,6 +3384,7 @@ void i915_gem_init_swizzling(struct drm_device *dev);
> > void i915_gem_cleanup_engines(struct drm_device *dev);
> > int __must_check i915_gem_wait_for_idle(struct drm_i915_private *dev_priv);
> > int __must_check i915_gem_suspend(struct drm_device *dev);
> > +void i915_gem_resume(struct drm_device *dev);
> > void __i915_add_request(struct drm_i915_gem_request *req,
> > struct drm_i915_gem_object *batch_obj,
> > bool flush_caches);
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index cf0e8aa8035c..8b42a5101f11 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -4974,6 +4974,35 @@ i915_gem_stop_engines(struct drm_device *dev)
> > dev_priv->gt.stop_engine(engine);
> > }
> >
> > +static int switch_to_kernel_context(struct drm_i915_private *dev_priv)
> > +{
> > + struct intel_engine_cs *engine;
> > +
> > + for_each_engine(engine, dev_priv) {
> > + struct drm_i915_gem_request *req;
> > + int ret;
> > +
> > + if (engine->last_context == NULL)
> > + continue;
> > +
> > + if (engine->last_context == dev_priv->kernel_context)
> > + continue;
> > +
> > + req = i915_gem_request_alloc(engine, dev_priv->kernel_context);
> > + if (IS_ERR(req))
> > + return PTR_ERR(req);
> > +
> > + ret = 0;
> > + if (!i915.enable_execlists)
> > + ret = i915_switch_context(req);
> > + i915_add_request_no_flush(req);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
> > +
>
> Why do you want keep this separate? Altho the evict one is a little
> bit different and as I didn't see any perf implications: Why not
> consolidate the evict one and this one and have i915_gem_idle which
> would park to default and wait for idle.

I found i915_gem_idle() to be easily confused with the idle functions we
call upon idling. And later on you will see that i915_gem_park() itself
is not common to anything but suspend. So I don't feel like introducing
that as nebulous concept. But with a functional change to evict noted,
we can share the switch-context code...
-Chris

--
Chris Wilson, Intel Open Source Technology Centre