Quoting Yao, Jia (2026-09-22 17:34:08) > Hi @Joonas Lahtinen, > > For RCS -> UNSET > For CCS > 1. Old compute runtime -> UNSET > 2. New compute runtime -> USER > > If we take there's only one compute runtime version, and priority USER > > UNSET? Where's the conflict come from?
See below. > But if we take there's more than one compute runtime version, and their > priority is equal, UNSET can cover USER, USER can cover UNSET, even with > two clients they could cover each other. I didn't follow this part. How does the priority come into play? We have to keep switching the mode as the DRM clients come and go. > We should take it easy. > Once we reached USER, set by new compute, we should latch it, for the WA has > been implemented by USER. That won't work. If you are running two different containers, you may have different compute runtime versions. Also, Mesa can be submitting to CCS too for async compute, AFAIK. To properly cover things, we should make it into per DRM-client setting and switch the mode accordingly when different DRM client is run. And for the given SKU with only one CCS, as explained earlier, it should be already guaranteed that two different DRM clients are not active on the hardware at the same time due to the address space mathing requirement between RCS and CCS. If this needs to be extended to multi CCS SKUs, then it'd be a bigger implementation effort. Regards, Joonas > > Thanks, > Jia > > > -----Original Message----- > > From: Joonas Lahtinen <[email protected]> > > Sent: Monday, September 21, 2026 11:47 PM > > To: Yao, Jia <[email protected]>; [email protected]; sashiko- > > [email protected] > > Cc: [email protected]; [email protected]; Roper, > > Matthew D <[email protected]>; Tvrtko Ursulin > > <[email protected]> > > Subject: RE: [PATCH v9] drm/i915/dg2: Add per-context control for > > Wa_22013059131 > > > > Quoting Yao, Jia (2026-09-21 20:33:03) > > > Hi @Lahtinen, Joonas, > > > > > > The key is LSC_CHICKEN_BIT_0 is a global register. > > > > > > Even we use per-client, we should consider the following cases: > > > > > > 1. Should conflicting configurations within a client be rejected? > > > I recommend the first setting should be latched. > > > > From uAPI perspective it would be simpler to set this at the DRM client > > level at > > once. However we don't seem to have such uAPI in active use currently (all > > drm_noop) so you'd have to compare the complexity between indirectly > > setting it at DRM client level by first created context or adding such an > > uAPI to > > set it explicitly per client. > > > > > 2. Should conflicting configurations across different clients be rejected? > > > I think the latter setting can cover previous one. > > > > DRM clients need to be indepenent from the driver perspective, we can't do > > that. > > > > The whole point of making it per DRM client is that given the impacted SKU > > only has 1 CCS engine. We have the address space matching requirement > > between CCS and RCS, so when both CCS and RCS are running, we know they > > belong to the same DRM client and thus they will not conflict with the WA > > mode. And if only one of them is running, there can be no conflict either > > as it's > > just one context. > > > > > Even like this, still can't cover all the race condition. > > > > Which race conditions do you think would remain? We definitely have to > > eliminate any race conditions to land this. > > > > Regards, Joonas
