linux-kernel - Re: [PATCH v4 09/11] drm/msm/A6XX: Add a flag to allow preemption to submitqueue

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Message-ID: <CAF6AEGv95t=ioPGYLi6CdEuQzx9GC9ehMaTyG03ucbdVHx3eEg@mail.gmail.com>
Date: Fri, 20 Sep 2024 10:29:44 -0700
From: Rob Clark <robdclark@...il.com>
To: Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc: Antonino Maniscalco <antomani103@...il.com>, Sean Paul <sean@...rly.run>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Abhinav Kumar <quic_abhinavk@...cinc.com>, 
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Jonathan Corbet <corbet@....net>, linux-arm-msm@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
	Neil Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH v4 09/11] drm/msm/A6XX: Add a flag to allow preemption to submitqueue_create

On Fri, Sep 20, 2024 at 9:54 AM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>
> On Tue, Sep 17, 2024 at 01:14:19PM +0200, Antonino Maniscalco wrote:
> > Some userspace changes are necessary so add a flag for userspace to
> > advertise support for preemption when creating the submitqueue.
> >
> > When this flag is not set preemption will not be allowed in the middle
> > of the submitted IBs therefore mantaining compatibility with older
> > userspace.
> >
> > The flag is rejected if preemption is not supported on the target, this
> > allows userspace to know whether preemption is supported.
>
> Just curious, what is the motivation behind informing userspace about
> preemption support?

I think I requested that, as a "just in case" (because it would
otherwise be awkward if we later needed to know the difference btwn
drm/sched "preemption" which can only happen before submit is written
to ring and "real" preemption)

BR,
-R

> -Akhil
>
> >
> > Signed-off-by: Antonino Maniscalco <antomani103@...il.com>
> > Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-QRD
> > ---
> >  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 12 ++++++++----
> >  drivers/gpu/drm/msm/msm_submitqueue.c |  3 +++
> >  include/uapi/drm/msm_drm.h            |  5 ++++-
> >  3 files changed, 15 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > index 736f475d696f..edbcb6d229ba 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > @@ -430,8 +430,10 @@ static void a7xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
> >       OUT_PKT7(ring, CP_SET_MARKER, 1);
> >       OUT_RING(ring, 0x101); /* IFPC disable */
> >
> > -     OUT_PKT7(ring, CP_SET_MARKER, 1);
> > -     OUT_RING(ring, 0x00d); /* IB1LIST start */
> > +     if (submit->queue->flags & MSM_SUBMITQUEUE_ALLOW_PREEMPT) {
> > +             OUT_PKT7(ring, CP_SET_MARKER, 1);
> > +             OUT_RING(ring, 0x00d); /* IB1LIST start */
> > +     }
> >
> >       /* Submit the commands */
> >       for (i = 0; i < submit->nr_cmds; i++) {
> > @@ -462,8 +464,10 @@ static void a7xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
> >                       update_shadow_rptr(gpu, ring);
> >       }
> >
> > -     OUT_PKT7(ring, CP_SET_MARKER, 1);
> > -     OUT_RING(ring, 0x00e); /* IB1LIST end */
> > +     if (submit->queue->flags & MSM_SUBMITQUEUE_ALLOW_PREEMPT) {
> > +             OUT_PKT7(ring, CP_SET_MARKER, 1);
> > +             OUT_RING(ring, 0x00e); /* IB1LIST end */
> > +     }
> >
> >       get_stats_counter(ring, REG_A7XX_RBBM_PERFCTR_CP(0),
> >               rbmemptr_stats(ring, index, cpcycles_end));
> > diff --git a/drivers/gpu/drm/msm/msm_submitqueue.c b/drivers/gpu/drm/msm/msm_submitqueue.c
> > index 0e803125a325..9b3ffca3f3b4 100644
> > --- a/drivers/gpu/drm/msm/msm_submitqueue.c
> > +++ b/drivers/gpu/drm/msm/msm_submitqueue.c
> > @@ -170,6 +170,9 @@ int msm_submitqueue_create(struct drm_device *drm, struct msm_file_private *ctx,
> >       if (!priv->gpu)
> >               return -ENODEV;
> >
> > +     if (flags & MSM_SUBMITQUEUE_ALLOW_PREEMPT && priv->gpu->nr_rings == 1)
> > +             return -EINVAL;
> > +
> >       ret = msm_gpu_convert_priority(priv->gpu, prio, &ring_nr, &sched_prio);
> >       if (ret)
> >               return ret;
> > diff --git a/include/uapi/drm/msm_drm.h b/include/uapi/drm/msm_drm.h
> > index 3fca72f73861..f37858db34e6 100644
> > --- a/include/uapi/drm/msm_drm.h
> > +++ b/include/uapi/drm/msm_drm.h
> > @@ -345,7 +345,10 @@ struct drm_msm_gem_madvise {
> >   * backwards compatibility as a "default" submitqueue
> >   */
> >
> > -#define MSM_SUBMITQUEUE_FLAGS (0)
> > +#define MSM_SUBMITQUEUE_ALLOW_PREEMPT        0x00000001
> > +#define MSM_SUBMITQUEUE_FLAGS                    ( \
> > +             MSM_SUBMITQUEUE_ALLOW_PREEMPT | \
> > +             0)
> >
> >  /*
> >   * The submitqueue priority should be between 0 and MSM_PARAM_PRIORITIES-1,
> >
> > --
> > 2.46.0
> >