Re: [PATCH] drm/msm: Add MSM_SUBMIT_BO_NO_IMPLICIT

[Rob Clark]

On Thu, Jan 5, 2023 at 4:49 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
>
> On Tue, Dec 06, 2022 at 11:21:23AM -0800, Rob Clark wrote:
> > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> >
> > In cases where implicit sync is used, it is still useful (for things
> > like sub-allocation, etc) to allow userspace to opt-out of implicit
> > sync on per-BO basis.
> >
> > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/msm/msm_drv.c        |  3 ++-
> >  drivers/gpu/drm/msm/msm_gem_submit.c | 11 +++++++++++
> >  include/uapi/drm/msm_drm.h           |  4 +++-
> >  3 files changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> > index 017a512982a2..e0e1199a822f 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.c
> > +++ b/drivers/gpu/drm/msm/msm_drv.c
> > @@ -45,9 +45,10 @@
> >   * - 1.7.0 - Add MSM_PARAM_SUSPENDS to access suspend count
> >   * - 1.8.0 - Add MSM_BO_CACHED_COHERENT for supported GPUs (a6xx)
> >   * - 1.9.0 - Add MSM_SUBMIT_FENCE_SN_IN
> > + * - 1.10.0 - Add MSM_SUBMIT_BO_NO_IMPLICIT
> >   */
> >  #define MSM_VERSION_MAJOR    1
> > -#define MSM_VERSION_MINOR    9
> > +#define MSM_VERSION_MINOR    10
> >  #define MSM_VERSION_PATCHLEVEL       0
> >
> >  static const struct drm_mode_config_funcs mode_config_funcs = {
> > diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> > index eb3536e3d66a..8bad07a04f85 100644
> > --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> > +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> > @@ -334,9 +334,20 @@ static int submit_fence_sync(struct msm_gem_submit *submit, bool no_implicit)
> >               if (ret)
> >                       return ret;
> >
> > +             /* If userspace has determined that explicit fencing is
> > +              * used, it can disable implicit sync on the entire
> > +              * submit:
> > +              */
> >               if (no_implicit)
> >                       continue;
> >
> > +             /* Otherwise userspace can ask for implicit sync to be
> > +              * disabled on specific buffers.  This is useful for internal
> > +              * usermode driver managed buffers, suballocation, etc.
> > +              */
> > +             if (submit->bos[i].flags & MSM_SUBMIT_BO_NO_IMPLICIT)
> > +                     continue;
> > +
> >               ret = drm_sched_job_add_implicit_dependencies(&submit->base,
>
> Won't this break shrinkers and fun stuff like that? It's why we added the
> new USAGE_OTHER fence slot at least, and also why I wonder whether we

Only if the entire explicit sync path was busted.. My daily driver for
email/docs/meet/chat/corpstuff is a 4G device and CrOS is all explicit
sync.. I would have found out rapidly and dramatically if it was
busted :-P

But seriously, this doesn't change what fences we attach to buffers,
only what the sched job waits on

> shouldn't push this into the helper to make the right call. Every driver
> kinda needs the same wheel.

We kinda already have moved everything we can (with the current
driver-specific-uabi model) to helpers, what is left is driver
specific ioctl parsing.  We absolutely should take a step back and
re-evaluate this before anyone else adds a new submit/execbuf ioctl.
For example, the driver specific ioctl could just have a pointer to a
drm_gem_submit_bo_table type structure, and then we could move the
whole thing to a helper.  Short of breaking the submit ioctl up (which
a uring type uabi would let us do), I think the next best thing is to
split out common cross-driver structs for common parts of
submit/execbuf.

BR,
-R

> -Daniel
>
> >                                                             obj,
> >                                                             write);
> > diff --git a/include/uapi/drm/msm_drm.h b/include/uapi/drm/msm_drm.h
> > index f54b48ef6a2d..329100016e7c 100644
> > --- a/include/uapi/drm/msm_drm.h
> > +++ b/include/uapi/drm/msm_drm.h
> > @@ -222,10 +222,12 @@ struct drm_msm_gem_submit_cmd {
> >  #define MSM_SUBMIT_BO_READ             0x0001
> >  #define MSM_SUBMIT_BO_WRITE            0x0002
> >  #define MSM_SUBMIT_BO_DUMP             0x0004
> > +#define MSM_SUBMIT_BO_NO_IMPLICIT      0x0008
> >
> >  #define MSM_SUBMIT_BO_FLAGS            (MSM_SUBMIT_BO_READ | \
> >                                       MSM_SUBMIT_BO_WRITE | \
> > -                                     MSM_SUBMIT_BO_DUMP)
> > +                                     MSM_SUBMIT_BO_DUMP | \
> > +                                     MSM_SUBMIT_BO_NO_IMPLICIT)
> >
> >  struct drm_msm_gem_submit_bo {
> >       __u32 flags;          /* in, mask of MSM_SUBMIT_BO_x */
> > --
> > 2.38.1
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch