[Intel-gfx] [PATCH] drm/i915/GuC: Combine the two kernel parameter into one

[Jeff McGee]

On Tue, Nov 15, 2016 at 10:06:47AM -0800, Srivatsa, Anusha wrote:
> 
> 
> >-----Original Message-----
> >From: Tvrtko Ursulin [mailto:tvrtko.ursulin at linux.intel.com]
> >Sent: Tuesday, November 15, 2016 2:31 AM
> >To: Srivatsa, Anusha <anusha.srivatsa at intel.com>; Mcgee, Jeff
> ><jeff.mcgee at intel.com>
> >Cc: Ursulin, Tvrtko <tvrtko.ursulin at intel.com>; intel-gfx at lists.freedesktop.org;
> >Vivi, Rodrigo <rodrigo.vivi at intel.com>
> >Subject: Re: [Intel-gfx] [PATCH] drm/i915/GuC: Combine the two kernel
> >parameter into one
> >
> >
> >On 14/11/2016 17:34, Srivatsa, Anusha wrote:
> >
> >[snip]
> >
> >>> One idea could be to hide the guc loading form the user altogether
> >>> and hence improve usability (decrease exposed complexity) by having
> >>> only two parameters; i915.enable_guc_scheduling and i915.enable_huc.
> >> That's a good point. But with this we will have two parameters (which kills the
> >point of why the patch was written in the first place), then we can rather leave it
> >the way it is. Right?
> >
> >For some reason I thought the HuC patch series add a another module
> >parameter.
> >
> >What is the failure mode for HuC is GuC firmware loading is disabled btw?
> 
> 
> Hi Tvrtko, in the function intel_guc_auth_huc() there is a check to see if GuC is loaded or not. If GuC loading has failed or loading is disabled, then HuC authentication does not happen.
> 
Yes, GuC must authenticate HuC firmware.

I am in favor of Tvrtko's suggestion for dropping i915.enable_guc_loading,
keeping i915.enable_guc_submission, and adding i915.enable_huc. If either of
the last two are enabled, GuC loading is implied. So kernel parameters are tied
to enabling specific functionality. I think the specific parameter for loading
is legacy from the first hurdle for GuC long ago. I assume we are not bound by
ABI to keep that around if it is no longer needed, yes?

The other thing I would want to reconsider is the "casual" enable vs. "force"
enable options. Does anyone remember why these 2 levels of enable have been
used. Maybe this is also a legacy. Can we just do a auto (-1), disable (0),
and enable (1)?