[Intel-gfx] [RFC] drm/i915: add slice shutdown debugfs interface

[Chris Wilson]

On Fri, Apr 07, 2017 at 12:11:18PM -0700, Dmitry Rogozhkin wrote:
> 
> 
> On 4/7/2017 11:50 AM, Chris Wilson wrote:
> >On Fri, Apr 07, 2017 at 03:41:41AM -0700, Dmitry Rogozhkin wrote:
> >>Slice shutdown override interface (i915_slice_enabled) permits
> >>to power on/off GPGPU slices in Gen8 and Gen9. This is helpful
> >>in performance investigations amd checking scalability across
> >>hw platforms.

A comment (both here in the changelog and debugfs) to say that this will
effect any lrc created after the write would be nice (and not affect
older ones) and might help prevent some confusion in future.

> >>diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> >>index 0dc1cc4..bc650df 100644
> >>--- a/drivers/gpu/drm/i915/intel_lrc.c
> >>+++ b/drivers/gpu/drm/i915/intel_lrc.c
> >>@@ -1732,7 +1732,7 @@ int logical_xcs_ring_init(struct intel_engine_cs *engine)
> >>  	 * No explicit RPCS request is needed to ensure full
> >>  	 * slice/subslice/EU enablement prior to Gen9.
> >>  	*/
> >>-	if (INTEL_GEN(dev_priv) < 9)
> >>+	if (INTEL_GEN(dev_priv) < 8)
> >Unrelated?
> Directly related. BDW also permits to program number of powered-on
> slices, but since (as written in the comment) by default all slices
> are enabled, there was no need to execute the below code. But if you
> want to switch slices on/off, you need to run it.

Ok, looks like we set has_slice_pg on bdw, so this will change the
currently executed code. Please make the changes to make_rpcs as a
seperate patch so we can check/bisect to this if required.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre