From: Daniel Vetter <daniel@ffwll.ch>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
Sumit Semwal <sumit.semwal@linaro.org>,
Daniel Vetter <daniel.vetter@ffwll.ch>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
"linaro-mm-sig@lists.linaro.org" <linaro-mm-sig@lists.linaro.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Sean Paul <seanpaul@google.com>, Zach Reizner <zachr@google.com>
Subject: Re: [PATCH] dma-buf: Wait on the reservation object when sync'ing before CPU access
Date: Tue, 21 Jun 2016 10:44:15 +0200 [thread overview]
Message-ID: <CAKMK7uHRATM5FFxF54C6LcBp+6h0yzbs+BmNK-2b5VO477-Abg@mail.gmail.com> (raw)
In-Reply-To: <1466492640-12551-1-git-send-email-chris@chris-wilson.co.uk>
On Tue, Jun 21, 2016 at 08:04:00AM +0100, Chris Wilson wrote:
> Rendering operations to the dma-buf are tracked implicitly via the
> reservation_object (dmabuf->resv). This is used to allow poll() to
> wait upon outstanding rendering (or just query the current status of
> rendering). The dma-buf sync ioctl allows userspace to prepare the
> dma-buf for CPU access, which should include waiting upon rendering.
> (Some drivers may need to do more work to ensure that the dma-buf mmap
> is coherent as well as complete.)
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: linux-media@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-kernel@vger.kernel.org
> ---
>
> I'm wondering whether it makes sense just to always do the wait first.
> It is one of the first operations every driver has to make. A driver
> that wants to implement it differently (e.g. they can special case
> native waits) will still require a wait on the reservation object to
> finish external rendering.
Worst case (if the driver uses reservation objects also internally) we'll
end up calling this twice. It should be cheap enough to do that. I'll add
a few folks who might want to chip in with an opinion ...
-Daniel
> -Chris
>
> ---
> drivers/dma-buf/dma-buf.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index ddaee60ae52a..123f14b8e882 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -586,6 +586,22 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
> }
> EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
>
> +static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
> + enum dma_data_direction direction)
> +{
> + bool write = (direction == DMA_BIDIRECTIONAL ||
> + direction == DMA_TO_DEVICE);
> + struct reservation_object *resv = dma_buf->resv;
> + long ret;
> +
> + /* Wait on any implicit rendering fences */
> + ret = reservation_object_wait_timeout_rcu(resv, write, true,
> + MAX_SCHEDULE_TIMEOUT);
> + if (ret < 0)
> + return ret;
> +
> + return 0;
> +}
>
> /**
> * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
> @@ -607,6 +623,8 @@ int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
>
> if (dmabuf->ops->begin_cpu_access)
> ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
> + else
> + ret = __dma_buf_begin_cpu_access(dmabuf, direction);
>
> return ret;
> }
> --
> 2.8.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
next prev parent reply other threads:[~2016-06-21 8:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-21 7:04 [PATCH] dma-buf: Wait on the reservation object when sync'ing before CPU access Chris Wilson
2016-06-21 8:44 ` Daniel Vetter [this message]
2016-08-15 15:37 ` [PATCH v2] " Chris Wilson
2016-08-15 15:42 ` Chris Wilson
2016-08-15 16:02 ` Daniel Vetter
2016-12-19 1:40 ` Inki Dae
2016-12-19 10:23 ` Chris Wilson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAKMK7uHRATM5FFxF54C6LcBp+6h0yzbs+BmNK-2b5VO477-Abg@mail.gmail.com \
--to=daniel@ffwll.ch \
--cc=chris@chris-wilson.co.uk \
--cc=daniel.vetter@ffwll.ch \
--cc=dri-devel@lists.freedesktop.org \
--cc=linaro-mm-sig@lists.linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=maarten.lankhorst@linux.intel.com \
--cc=seanpaul@google.com \
--cc=sumit.semwal@linaro.org \
--cc=zachr@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).