Re: [PATCH v7 05/15] dma-buf/sync_file: Add SET_DEADLINE ioctl

[Rob Clark]

On Tue, Feb 28, 2023 at 1:22 AM Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote:
>
> On Mon, 27 Feb 2023 11:35:11 -0800
> Rob Clark <robdclark@xxxxxxxxx> wrote:
>
> > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> >
> > The initial purpose is for igt tests, but this would also be useful for
> > compositors that wait until close to vblank deadline to make decisions
> > about which frame to show.
> >
> > The igt tests can be found at:
> >
> > https://gitlab.freedesktop.org/robclark/igt-gpu-tools/-/commits/fence-deadline
> >
> > v2: Clarify the timebase, add link to igt tests
> > v3: Use u64 value in ns to express deadline.
> > v4: More doc
> >
> > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > ---
> >  drivers/dma-buf/dma-fence.c    |  3 ++-
> >  drivers/dma-buf/sync_file.c    | 19 +++++++++++++++++++
> >  include/uapi/linux/sync_file.h | 22 ++++++++++++++++++++++
> >  3 files changed, 43 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index e103e821d993..7761ceeae620 100644
> > --- a/drivers/dma-buf/dma-fence.c
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -933,7 +933,8 @@ EXPORT_SYMBOL(dma_fence_wait_any_timeout);
> >   *   the GPU's devfreq to reduce frequency, when in fact the opposite is what is
> >   *   needed.
> >   *
> > - * To this end, deadline hint(s) can be set on a &dma_fence via &dma_fence_set_deadline.
> > + * To this end, deadline hint(s) can be set on a &dma_fence via &dma_fence_set_deadline
> > + * (or indirectly via userspace facing ioctls like &SYNC_IOC_SET_DEADLINE).
> >   * The deadline hint provides a way for the waiting driver, or userspace, to
> >   * convey an appropriate sense of urgency to the signaling driver.
>
> Hi,
>
> when the kernel HTML doc is generated, I assume the above becomes a
> link to "DOC: SYNC_IOC_SET_DEADLINE - set a deadline on a fence", right?

Heh, kernel docs completely miss the sync_file uABI.. I'll add a patch
to correct that in order to make these links work properly.

BR,
-R

> >   *
> > diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
> > index af57799c86ce..418021cfb87c 100644
> > --- a/drivers/dma-buf/sync_file.c
> > +++ b/drivers/dma-buf/sync_file.c
> > @@ -350,6 +350,22 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >       return ret;
> >  }
> >
> > +static int sync_file_ioctl_set_deadline(struct sync_file *sync_file,
> > +                                     unsigned long arg)
> > +{
> > +     struct sync_set_deadline ts;
> > +
> > +     if (copy_from_user(&ts, (void __user *)arg, sizeof(ts)))
> > +             return -EFAULT;
> > +
> > +     if (ts.pad)
> > +             return -EINVAL;
> > +
> > +     dma_fence_set_deadline(sync_file->fence, ns_to_ktime(ts.deadline_ns));
> > +
> > +     return 0;
> > +}
> > +
> >  static long sync_file_ioctl(struct file *file, unsigned int cmd,
> >                           unsigned long arg)
> >  {
> > @@ -362,6 +378,9 @@ static long sync_file_ioctl(struct file *file, unsigned int cmd,
> >       case SYNC_IOC_FILE_INFO:
> >               return sync_file_ioctl_fence_info(sync_file, arg);
> >
> > +     case SYNC_IOC_SET_DEADLINE:
> > +             return sync_file_ioctl_set_deadline(sync_file, arg);
> > +
> >       default:
> >               return -ENOTTY;
> >       }
> > diff --git a/include/uapi/linux/sync_file.h b/include/uapi/linux/sync_file.h
> > index ee2dcfb3d660..49325cf6749b 100644
> > --- a/include/uapi/linux/sync_file.h
> > +++ b/include/uapi/linux/sync_file.h
> > @@ -67,6 +67,21 @@ struct sync_file_info {
> >       __u64   sync_fence_info;
> >  };
> >
> > +/**
> > + * struct sync_set_deadline - set a deadline hint on a fence
> > + * @deadline_ns: absolute time of the deadline
>
> Is it legal to pass zero as deadline_ns?
>
> > + * @pad:     must be zero
> > + *
> > + * The timebase for the deadline is CLOCK_MONOTONIC (same as vblank)
>
> Does something here provide doc links to "DOC: SYNC_IOC_SET_DEADLINE -
> set a deadline on a fence" and to the "DOC: deadline hints"?
>
> > + */
> > +struct sync_set_deadline {
> > +     __u64   deadline_ns;
> > +     /* Not strictly needed for alignment but gives some possibility
> > +      * for future extension:
> > +      */
> > +     __u64   pad;
> > +};
> > +
> >  #define SYNC_IOC_MAGIC               '>'
> >
> >  /**
> > @@ -95,4 +110,11 @@ struct sync_file_info {
> >   */
> >  #define SYNC_IOC_FILE_INFO   _IOWR(SYNC_IOC_MAGIC, 4, struct sync_file_info)
> >
> > +/**
> > + * DOC: SYNC_IOC_SET_DEADLINE - set a deadline on a fence
> > + *
> > + * Allows userspace to set a deadline on a fence, see dma_fence_set_deadline()
>
> Does something here provide doc links to struct sync_set_deadline and
> to the "DOC: deadline hints"?
>
> > + */
> > +#define SYNC_IOC_SET_DEADLINE        _IOW(SYNC_IOC_MAGIC, 5, struct sync_set_deadline)
> > +
> >  #endif /* _UAPI_LINUX_SYNC_H */
>
> With all those links added:
> Acked-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
>
>
> Thanks,
> pq