Re: [PATCH 3/9] drm/xe/rtp: Keep track of non-OA nonpriv slots

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Fri, 29 May 2026 16:24:30 -0700, Umesh Nerlige Ramappa wrote:
>
> On Fri, May 29, 2026 at 01:45:12PM -0700, Dixit, Ashutosh wrote:
> > On Fri, 29 May 2026 11:30:34 -0700, Umesh Nerlige Ramappa wrote:
> >>
> >> On Mon, May 18, 2026 at 04:47:10PM -0700, Ashutosh Dixit wrote:
> >> > In order to dynamically whitelist/dewhitelist OA registers on OA stream
> >> > open/close, we need to keep track of nonpriv slots occupied by non-OA
> >> > register whitelists.
> >>
> >> Can we maintain the slot index within hwe, so that the caller does not need
> >> to keep track of it? I am assuming this will only be used in the probe
> >> path. For all other paths the *_sr registers are used directly which
> >> already have the registre<->slot association stored within them.
> >>
> >> i.e.
> >>
> >> hwe->slot;
> >
> > Hmm, when I first wrote the code, I had this in hwe: hwe->nonpriv_slots.
> > But later realized it is only needed in xe_reg_whitelist_process_engine(),
> > so moved it to the local variable nonpriv_slots there.
> >
> > Also, nonpriv_slots is actually number of slots occupied by non-OA
> > registers. So if it part of hwe, the question becomes more complicated:
> > what do we store there, number of slots excluding OA or including OA? Since
> > we only need number of slots excluding OA.
>
> I would just think of it as the next available nonpriv slot for the caller
> to use. It's just a state w.r.t the hwe. When you let the caller (even if
> internal to the KMD) manage it, it's prone to errors - not about this
> series or current code, but in general.

OK, will do this in v2. Thanks.

> >
> > Therefore, to avoid these complications, I decided that the best way was a
> > temporary local variable.
> >
> > What do you think we'd gain by maintaining it as part of hwe? If things
> > change later, we could add it, but for now the local variable seems
> > sufficient?
>
> >
> > Thanks.
> > --
> > Ashutosh
> >
> >> >
> >> > Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
> >> > ---
> >> > drivers/gpu/drm/xe/xe_reg_whitelist.c | 8 ++++++--
> >> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >> >
> >> > diff --git a/drivers/gpu/drm/xe/xe_reg_whitelist.c b/drivers/gpu/drm/xe/xe_reg_whitelist.c
> >> > index 6cc81f53fc601..1e788e2ee4014 100644
> >> > --- a/drivers/gpu/drm/xe/xe_reg_whitelist.c
> >> > +++ b/drivers/gpu/drm/xe/xe_reg_whitelist.c
> >> > @@ -159,7 +159,7 @@ static const struct xe_rtp_entry_sr oa_whitelist[] = {
> >> >	},
> >> > };
> >> >
> >> > -static void whitelist_apply_to_hwe(struct xe_hw_engine *hwe)
> >> > +static int whitelist_apply_to_hwe(struct xe_hw_engine *hwe)
> >> > {
> >> >	struct xe_reg_sr *sr = &hwe->reg_whitelist;
> >> >	struct xe_reg_sr_entry *entry;
> >> > @@ -191,6 +191,8 @@ static void whitelist_apply_to_hwe(struct xe_hw_engine *hwe)
> >> >
> >> >		slot++;
> >> >	}
> >> > +
> >> > +	return slot;
> >> > }
> >> >
> >> > /**
> >> > @@ -203,11 +205,13 @@ static void whitelist_apply_to_hwe(struct xe_hw_engine *hwe)
> >> >  */
> >> > void xe_reg_whitelist_process_engine(struct xe_hw_engine *hwe)
> >> > {
> >> > +	int nonpriv_slots;
> >> > +
> >> >	struct xe_rtp_process_ctx ctx = XE_RTP_PROCESS_CTX_INITIALIZER(hwe);
> >> >
> >> >	xe_rtp_process_to_sr(&ctx, register_whitelist, ARRAY_SIZE(register_whitelist),
> >> >			     &hwe->reg_whitelist, false);
> >> > -	whitelist_apply_to_hwe(hwe);
> >> > +	nonpriv_slots = whitelist_apply_to_hwe(hwe);
> >> >
> >> >	xe_rtp_process_to_sr(&ctx, oa_whitelist, ARRAY_SIZE(oa_whitelist),
> >> >			     &hwe->oa_whitelist, false);
> >> > --
> >> > 2.54.0
> >> >