From: Rob Herring <robh@kernel.org>
To: Brian Starkey <brian.starkey@arm.com>
Cc: John Stultz <john.stultz@linaro.org>,
Robin Murphy <robin.murphy@arm.com>,
lkml <linux-kernel@vger.kernel.org>,
Sumit Semwal <sumit.semwal@linaro.org>,
"Andrew F. Davis" <afd@ti.com>,
Benjamin Gaignard <benjamin.gaignard@linaro.org>,
Liam Mark <lmark@codeaurora.org>,
Pratik Patel <pratikp@codeaurora.org>,
Laura Abbott <labbott@redhat.com>, Chenbo Feng <fengc@google.com>,
Alistair Strachan <astrachan@google.com>,
Sandeep Patil <sspatil@google.com>,
Hridya Valsaraju <hridya@google.com>,
Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Andrew Morton <akpm@linux-foundation.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
linux-mm <linux-mm@kvack.org>, nd <nd@arm.com>
Subject: Re: [RFC][PATCH 3/4] dma-buf: cma_heap: Extend logic to export CMA regions tagged with "linux,cma-heap"
Date: Tue, 12 May 2020 11:37:14 -0500 [thread overview]
Message-ID: <20200512163714.GA22577@bogus> (raw)
In-Reply-To: <20200504090628.d2q32dwyg6em5pp7@DESKTOP-E1NTVVP.localdomain>
On Mon, May 04, 2020 at 10:06:28AM +0100, Brian Starkey wrote:
> On Fri, May 01, 2020 at 12:01:40PM -0700, John Stultz wrote:
> > On Fri, May 1, 2020 at 4:08 AM Robin Murphy <robin.murphy@arm.com> wrote:
> > >
> > > On 2020-05-01 11:21 am, Brian Starkey wrote:
> > > > Hi John,
> > > >
> > > > On Fri, May 01, 2020 at 07:39:48AM +0000, John Stultz wrote:
> > > >> This patch reworks the cma_heap initialization so that
> > > >> we expose both the default CMA region and any CMA regions
> > > >> tagged with "linux,cma-heap" in the device-tree.
> > > >>
> > > >> Cc: Rob Herring <robh+dt@kernel.org>
> > > >> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> > > >> Cc: "Andrew F. Davis" <afd@ti.com>
> > > >> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> > > >> Cc: Liam Mark <lmark@codeaurora.org>
> > > >> Cc: Pratik Patel <pratikp@codeaurora.org>
> > > >> Cc: Laura Abbott <labbott@redhat.com>
> > > >> Cc: Brian Starkey <Brian.Starkey@arm.com>
> > > >> Cc: Chenbo Feng <fengc@google.com>
> > > >> Cc: Alistair Strachan <astrachan@google.com>
> > > >> Cc: Sandeep Patil <sspatil@google.com>
> > > >> Cc: Hridya Valsaraju <hridya@google.com>
> > > >> Cc: Christoph Hellwig <hch@lst.de>
> > > >> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> > > >> Cc: Robin Murphy <robin.murphy@arm.com>
> > > >> Cc: Andrew Morton <akpm@linux-foundation.org>
> > > >> Cc: devicetree@vger.kernel.org
> > > >> Cc: dri-devel@lists.freedesktop.org
> > > >> Cc: linux-mm@kvack.org
> > > >> Signed-off-by: John Stultz <john.stultz@linaro.org>
> > > >> ---
> > > >> drivers/dma-buf/heaps/cma_heap.c | 18 +++++++++---------
> > > >> 1 file changed, 9 insertions(+), 9 deletions(-)
> > > >>
> > > >> diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
> > > >> index 626cf7fd033a..dd154e2db101 100644
> > > >> --- a/drivers/dma-buf/heaps/cma_heap.c
> > > >> +++ b/drivers/dma-buf/heaps/cma_heap.c
> > > >> @@ -141,6 +141,11 @@ static int __add_cma_heap(struct cma *cma, void *data)
> > > >> {
> > > >> struct cma_heap *cma_heap;
> > > >> struct dma_heap_export_info exp_info;
> > > >> + struct cma *default_cma = dev_get_cma_area(NULL);
> > > >> +
> > > >> + /* We only add the default heap and explicitly tagged heaps */
> > > >> + if (cma != default_cma && !cma_dma_heap_enabled(cma))
> > > >> + return 0;
> > > >
> > > > Thinking about the pl111 thread[1], I'm wondering if we should also
> > > > let drivers call this directly to expose their CMA pools, even if they
> > > > aren't tagged for dma-heaps in DT. But perhaps that's too close to
> > > > policy.
> > >
> > > That sounds much like what my first thoughts were - apologies if I'm
> > > wildly off-base here, but as far as I understand:
> > >
> > > - Device drivers know whether they have their own "memory-region" or not.
> > > - Device drivers already have to do *something* to participate in dma-buf.
> > > - Device drivers know best how they make use of both the above.
> > > - Therefore couldn't it be left to drivers to choose whether to register
> > > their CMA regions as heaps, without having to mess with DT at all?
+1, but I'm biased toward any solution not using DT. :)
> > I guess I'm not opposed to this. But I guess I'd like to see some more
> > details? You're thinking the pl111 driver would add the
> > "memory-region" node itself?
> >
> > Assuming that's the case, my only worry is what if that memory-region
> > node isn't a CMA area, but instead something like a carveout? Does the
> > driver need to parse enough of the dt to figure out where to register
> > the region as a heap?
>
> My thinking was more like there would already be a reserved-memory
> node in DT for the chunk of memory, appropriately tagged so that it
> gets added as a CMA region.
>
> The device's node would have "memory-region=<&blah>;" and would use
> of_reserved_mem_device_init() to link up dev->cma_area to the
> corresponding cma region.
>
> So far, that's all in-place already. The bit that's missing is
> exposing that dev->cma_area to userspace as a dma_heap - so we could
> just have "int cma_heap_add(struct cma *cma)" or "int
> cma_heap_dev_add(struct device *dev)" or something exported for
> drivers to expose their device-assigned cma region if they wanted to.
>
> I don't think this runs into the lifetime problems of generalised
> heaps-as-modules either, because the CMA region will never go away
> even if the driver does.
>
> Alongside that, I do think the completely DT-driven approach can be
> useful too - because there may be regions which aren't associated with
> any specific device driver, that we want exported as heaps.
And they are associated with the hardware description rather than the
userspace environment?
Rob
next prev parent reply other threads:[~2020-05-12 16:37 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-01 7:39 [RFC][PATCH 0/4] Support non-default CMA regions to the dmabuf heaps interface John Stultz
2020-05-01 7:39 ` [RFC][PATCH 1/4] devicetree: bindings: Add linux,cma-heap tag for reserved memory John Stultz
2020-05-01 10:42 ` Brian Starkey
2020-05-01 18:40 ` John Stultz
2020-05-04 8:50 ` Brian Starkey
2020-05-06 16:04 ` Andrew F. Davis
2020-05-06 16:30 ` John Stultz
2020-05-06 17:35 ` Andrew F. Davis
2020-05-06 18:34 ` John Stultz
2020-05-01 7:39 ` [RFC][PATCH 2/4] mm: cma: Add dma_heap flag to cma structure John Stultz
2020-05-01 10:48 ` Brian Starkey
2020-05-01 18:42 ` John Stultz
2020-05-01 7:39 ` [RFC][PATCH 3/4] dma-buf: cma_heap: Extend logic to export CMA regions tagged with "linux,cma-heap" John Stultz
2020-05-01 10:21 ` Brian Starkey
2020-05-01 11:08 ` Robin Murphy
2020-05-01 19:01 ` John Stultz
2020-05-04 9:06 ` Brian Starkey
2020-05-12 16:37 ` Rob Herring [this message]
2020-05-13 10:44 ` Brian Starkey
2020-05-14 14:52 ` Rob Herring
2020-05-15 9:32 ` Brian Starkey
2020-05-01 7:39 ` [RFC][PATCH 4/4] example: dts: hi3660-hikey960: Add dts entries to test cma heap binding John Stultz
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=20200512163714.GA22577@bogus \
--to=robh@kernel.org \
--cc=afd@ti.com \
--cc=akpm@linux-foundation.org \
--cc=astrachan@google.com \
--cc=benjamin.gaignard@linaro.org \
--cc=brian.starkey@arm.com \
--cc=devicetree@vger.kernel.org \
--cc=dri-devel@lists.freedesktop.org \
--cc=fengc@google.com \
--cc=hch@lst.de \
--cc=hridya@google.com \
--cc=john.stultz@linaro.org \
--cc=labbott@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lmark@codeaurora.org \
--cc=m.szyprowski@samsung.com \
--cc=nd@arm.com \
--cc=pratikp@codeaurora.org \
--cc=robin.murphy@arm.com \
--cc=sspatil@google.com \
--cc=sumit.semwal@linaro.org \
/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).