From: Ofir Bitton <obitton@habana.ai>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jason Gunthorpe <jgg@ziepe.ca>,
Oded Gabbay <oded.gabbay@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
SW_Drivers <SW_Drivers@habana.ai>
Subject: RE: [PATCH 1/3] habanalabs: implement dma-fence mechanism
Date: Tue, 14 Jul 2020 12:07:29 +0000 [thread overview]
Message-ID: <VI1PR0202MB32774769723B6CE154865086BC610@VI1PR0202MB3277.eurprd02.prod.outlook.com> (raw)
In-Reply-To: <20200714063648.GC662760@kroah.com>
Sure,
I will send a new patch using completion instead of dma-fence
Thanks,
Ofir
-----Original Message-----
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Sent: Tuesday, July 14, 2020 09:37
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jason Gunthorpe <jgg@ziepe.ca>; Oded Gabbay <oded.gabbay@gmail.com>; Linux Kernel Mailing List <linux-kernel@vger.kernel.org>; SW_Drivers <SW_Drivers@habana.ai>; Ofir Bitton <obitton@habana.ai>
Subject: Re: [PATCH 1/3] habanalabs: implement dma-fence mechanism
On Mon, Jul 13, 2020 at 09:08:55PM +0200, Daniel Vetter wrote:
> On Mon, Jul 13, 2020 at 9:03 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> >
> > On Mon, Jul 13, 2020 at 08:34:12PM +0200, Daniel Vetter wrote:
> > > On Mon, Jul 13, 2020 at 5:57 PM Greg Kroah-Hartman
> > > <gregkh@linuxfoundation.org> wrote:
> > > >
> > > > On Mon, Jul 13, 2020 at 06:54:22PM +0300, Oded Gabbay wrote:
> > > > > From: Ofir Bitton <obitton@habana.ai>
> > > > >
> > > > > Instead of using standard dma-fence mechanism designed for
> > > > > GPU's, we introduce our own implementation based on the former
> > > > > one. This implementation is much more sparse than the
> > > > > original, contains only mandatory functionality required by the driver.
> > > >
> > > > Sad you can't use the in-kernel code for this, I really don't
> > > > understand what's wrong with using it as-is.
> > > >
> > > > Daniel, why do we need/want duplicate code floating around in
> > > > the tree like this?
> > >
> > > The rules around dma-fence are ridiculously strict, and it only
> > > makes sense to inflict that upon you if you actually want to
> > > participate in the cross driver uapi built up around dma-buf and dma-fence.
> > >
> > > I've recently started some lockdep annotations to better enforce
> > > these rules (and document them), and it's finding tons of subtle
> > > bugs even in drivers/gpu (and I only just started with annotating drivers:
> > >
> > > https://lore.kernel.org/dri-devel/20200707201229.472834-1-daniel.v
> > > etter@ffwll.ch/
> > >
> > > You really don't want to deal with this if you don't have to. If
> > > drivers/gpu folks (who created this) aren't good enough to
> > > understand it, maybe it's not a good idea to sprinkle this all
> > > over the tree. And fundamentally all this is is a slightly fancier
> > > struct completion. Use that one instead, or a wait_queue.
> > >
> > > I discussed this a bit with Oded, and he thinks it's easier to
> > > copypaste and simplify, but given that all other drivers seem to
> > > get by perfectly well with completion or wait_queue, I'm not sure
> > > that's a solid case.
> > >
> > > Also adding Jason Gunthorpe, who very much suggested this should
> > > be limited to dma-buf/gpu related usage only.
> >
> > Without all the cross-driver stuff dma_fence is just a completion.
> > Using dma_fence to get a completion is big abuse of what it is
> > intended for.
> >
> > I think the only problem with this patch is that it keeps too much
> > of the dma_fence stuff around. From what I could tell it really just
> > wants to add a kref and completion to struct hl_cs_compl and delete
> > everything to do with dma_fence.
>
> Yeah, that's what I recommended doing too. error flag might be needed
> too I think, but that's it.
Ok, so this should be made much simpler and not use this copy/paste code at all. I can accept that :)
Ofir, care to redo this?
thanks,
greg k-h
prev parent reply other threads:[~2020-07-14 12:07 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 15:54 [PATCH 1/3] habanalabs: implement dma-fence mechanism Oded Gabbay
2020-07-13 15:54 ` [PATCH 2/3] habanalabs: create common folder Oded Gabbay
2020-07-15 10:56 ` Omer Shpigelman
2020-07-13 15:54 ` [PATCH 3/3] habanalabs: update hl_boot_if.h from firmware Oded Gabbay
2020-07-15 10:58 ` Omer Shpigelman
2020-07-13 15:57 ` [PATCH 1/3] habanalabs: implement dma-fence mechanism Greg Kroah-Hartman
2020-07-13 18:34 ` Daniel Vetter
2020-07-13 19:03 ` Jason Gunthorpe
2020-07-13 19:08 ` Daniel Vetter
2020-07-14 6:36 ` Greg Kroah-Hartman
2020-07-14 12:07 ` Ofir Bitton [this message]
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