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

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Message-ID: <20240923194449.vffhq7ppkzxtx5bl@hu-akhilpo-hyd.qualcomm.com>
Date: Tue, 24 Sep 2024 01:14:49 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Rob Clark <robdclark@...il.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 10:29:44AM -0700, Rob Clark wrote:
> 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)

Thanks. That makes sense.

-Akhil

> 
> 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
> > >