Re: [PATCH v2 1/1] drm/i915/pxp: Add missing tag for Wa_14019159160

["Teres Alexis, Alan Previn" <alan.previn.teres.alexis@intel.com>]

On Wed, 2023-11-29 at 13:13 -0800, Teres Alexis, Alan Previn wrote:
> On Mon, 2023-11-27 at 15:24 -0500, Vivi, Rodrigo wrote:
> > On Wed, Nov 22, 2023 at 12:30:03PM -0800, Alan Previn wrote:
> alan:snip
> alan: thanks for reviewing and apologize for replying to this late.
> 
> > >  	/*
> > > -	 * On MTL and newer platforms, protected contexts require setting
> > > -	 * the LRC run-alone bit or else the encryption will not happen.
> > > +	 * Wa_14019159160 - Case 2: mtl
> > > +	 * On some platforms, protected contexts require setting
> > > +	 * the LRC run-alone bit or else the encryption/decryption will not happen.
> > > +	 * NOTE: Case 2 only applies to PXP use-case of said workaround.
> > >  	 */
> > 
> > hmm, interesting enough, on the wa description I read that it is incomplete for MTL/ARL
> > and something about a fuse bit. We should probably chase for some clarification in the
> > HSD?!
> alan: yes, i went through the HSD description with the architect and we both had agreed that
> that from the KMD's perspective. At that time, the checking of the fuse from KMD's
> could be optimized out for Case-2-PXP: if the fuses was set a certain way, KMD can skip setting
> the bit in lrc because hw will enforce runalone in pxp mode irrespective of what KMD does but
> if fuse was was not set that way KMD needed to set the runalone in lrc. So for case2, its simpler
> to just turn it on always when the context is protected. However, that said, i realized the
> wording of the HSDs have changed since the original patch was implemented so i will reclarify
> offline and reply back. NOTE: i believe John Harrison is working on case-3 through a
> separate series.
alan: based on conversations with the architect, a different WA number, 14019725520,
has the details of case-2 that explains the relationship the new fuse.
However, as before it can be optimized as explained above where PXP context
need to always set this bit to ensure encryption/decryption engages.