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From:   Oded Gabbay <oded.gabbay@gmail.com>
Date:   Mon, 11 May 2020 12:43:09 +0300
Message-ID: <CAFCwf11MrovJbcutkuyhJpvAY9v9rtRdHAkY8wJF7S-z5vrWTg@mail.gmail.com>
Subject: Re: [PATCH 3/3] misc/habalabs: don't set default fence_ops->wait
To:     Daniel Vetter <daniel.vetter@ffwll.ch>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Olof Johansson <olof@lixom.net>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org
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Sender: linux-kernel-owner@vger.kernel.org
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And just FYI, the driver was written internally at 2016-17, where the
dma-buf module didn't check the .wait ops before calling it and that's
why the initialization of the default wait was there in the first
place.
I should have removed it when I upstreamed it but it missed my review.
Thanks,
Oded

On Mon, May 11, 2020 at 12:36 PM Oded Gabbay <oded.gabbay@gmail.com> wrote:
>
> On Mon, May 11, 2020 at 12:11 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > It's the default.
> Thanks for catching that.
>
> >
> > Also so much for "we're not going to tell the graphics people how to
> > review their code", dma_fence is a pretty core piece of gpu driver
> > infrastructure. And it's very much uapi relevant, including piles of
> > corresponding userspace protocols and libraries for how to pass these
> > around.
> >
> > Would be great if habanalabs would not use this (from a quick look
> > it's not needed at all), since open source the userspace and playing
> > by the usual rules isn't on the table. If that's not possible (because
> > it's actually using the uapi part of dma_fence to interact with gpu
> > drivers) then we have exactly what everyone promised we'd want to
> > avoid.
>
> We don't use the uapi parts, we currently only using the fencing and
> signaling ability of this module inside our kernel code. But maybe I
> didn't understand what you request. You want us *not* to use this
> well-written piece of kernel code because it is only used by graphics
> drivers ?
> I'm sorry but I don't get this argument, if this is indeed what you meant.
>
> Oded
>
> >
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc:     Olof Johansson <olof@lixom.net>
> > Cc: Oded Gabbay <oded.gabbay@gmail.com>
> > Cc: Sumit Semwal <sumit.semwal@linaro.org>
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > ---
> >  drivers/misc/habanalabs/command_submission.c | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/drivers/misc/habanalabs/command_submission.c b/drivers/misc/habanalabs/command_submission.c
> > index 409276b6374d..cc3ce759b6c3 100644
> > --- a/drivers/misc/habanalabs/command_submission.c
> > +++ b/drivers/misc/habanalabs/command_submission.c
> > @@ -46,7 +46,6 @@ static const struct dma_fence_ops hl_fence_ops = {
> >         .get_driver_name = hl_fence_get_driver_name,
> >         .get_timeline_name = hl_fence_get_timeline_name,
> >         .enable_signaling = hl_fence_enable_signaling,
> > -       .wait = dma_fence_default_wait,
> >         .release = hl_fence_release
> >  };
> >
> > --
> > 2.26.2
> >