[Intel-gfx] [PATCH v2] drm/i915/execlists: Refactor common engine setup

[Chris Wilson]

On Fri, Apr 29, 2016 at 11:11:20AM +0100, Tvrtko Ursulin wrote:
> 
> On 29/04/16 11:00, Chris Wilson wrote:
> >On Fri, Apr 29, 2016 at 10:50:02AM +0100, Tvrtko Ursulin wrote:
> >>
> >>On 29/04/16 10:39, Chris Wilson wrote:
> >>>On Fri, Apr 29, 2016 at 10:25:41AM +0100, Tvrtko Ursulin wrote:
> >>>>On 29/04/16 10:15, Chris Wilson wrote:
> >>>>>diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> >>>>>index 2e0eaa9fa240..2c94072ab085 100644
> >>>>>--- a/drivers/gpu/drm/i915/intel_lrc.c
> >>>>>+++ b/drivers/gpu/drm/i915/intel_lrc.c
> >>>>>@@ -2016,14 +2016,17 @@ logical_ring_setup(struct drm_device *dev, enum intel_engine_id id)
> >>>>>         struct intel_engine_cs *engine = &dev_priv->engine[id];
> >>>>>         enum forcewake_domains fw_domains;
> >>>>>
> >>>>>-       engine->dev = dev;
> >>>>>-
> >>>>>         engine->id = id;
> >>>>>         engine->name = info->name;
> >>>>>         engine->exec_id = info->exec_id;
> >>>>>         engine->guc_id = info->guc_id;
> >>>>>         engine->mmio_base = info->mmio_base;
> >>>>>
> >>>>>+       /* disable interrupts to this engine before we install ourselves*/
> >>>>>+       I915_WRITE_IMR(engine, ~0);
> >>>>>+
> >>>>>+       engine->dev = dev;
> >>>>>+
> >>>>>         /* Intentionally left blank. */
> >>>>>         engine->buffer = NULL;
> >>>>>
> >>>>>Make sense?
> >>>>
> >>>>Not the most elegant because all the hw access we have so far is in
> >>>>engine->init_hw. Why can't we just make intel_engine_initialized
> >>>>return false until the very last thing in engine constructors?
> >>>
> >>>In my defence sanitizing the hw before we are ready is common practice
> >>>across the driver. The unfun part is that irq install is before gem_init
> >>>(because modeset init wants irq enabled for GMBUS/dp-aux). gem init
> >>>itself could be split up and moved around so that the setup and init_hw
> >>>phases are separate (which would be next on the init ordering hitlist I
> >>>hope).
> >>>
> >>>I want engine->dev/engine->i915 set early so we can use it during setup
> >>>and init-hw and so that for_each_engine() works as expected in that
> >>>time.
> >>
> >>Why wouldn't an explicit engine->initialized flag solve that? You
> >>could keep setting engine->dev early (as it should be) and then set
> >>engine->initialized at the end of per-engine constructors.
> >
> >Because it becomes irrelevant very shortly. The only interesting
> >question remaining is whether or not we should be sanitizing the IMR
> >first. It has been suggested elsewhere (in Ville's review of the GT
> >interrupt handling) that doing the sanitization would be useful.
> 
> How come it becomes irrelevant? Will there not be
> intel_engine_initialized? Because as long as there is, imho it makes
> sense not to use engine->dev for it.

The only argument here is how to handle an interrupt left over from
before the driver loads. At all other times engine->dev means precisely
that. I do not agree that you need to duplicate the state.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre