linux-kernel - Re: [RESEND][PATCH v8 0/5] DMA-BUF Heaps (destaging ION)

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Date:   Wed, 16 Oct 2019 10:34:01 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Ayan Halder <Ayan.Halder@....com>
Cc:     Sumit Semwal <sumit.semwal@...aro.org>,
        Sudipto Paul <Sudipto.Paul@....com>,
        Vincent Donnefort <Vincent.Donnefort@....com>,
        Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        Liam Mark <lmark@...eaurora.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@...radead.org>,
        DRI mailing list <dri-devel@...ts.freedesktop.org>,
        "Andrew F . Davis" <afd@...com>,
        Hridya Valsaraju <hridya@...gle.com>, nd <nd@....com>,
        Pratik Patel <pratikp@...eaurora.org>
Subject: Re: [RESEND][PATCH v8 0/5] DMA-BUF Heaps (destaging ION)

On Wed, Oct 9, 2019 at 10:38 AM Ayan Halder <Ayan.Halder@....com> wrote:
>
> On Tue, Sep 24, 2019 at 04:22:18PM +0000, Ayan Halder wrote:
> > On Thu, Sep 19, 2019 at 10:21:52PM +0530, Sumit Semwal wrote:
> > > Hello Christoph, everyone,
> > >
> > > On Sat, 7 Sep 2019 at 00:17, John Stultz <john.stultz@...aro.org> wrote:
> > > >
> > > > Here is yet another pass at the dma-buf heaps patchset Andrew
> > > > and I have been working on which tries to destage a fair chunk
> > > > of ION functionality.
> > > >
> > > > The patchset implements per-heap devices which can be opened
> > > > directly and then an ioctl is used to allocate a dmabuf from the
> > > > heap.
> > > >
> > > > The interface is similar, but much simpler then IONs, only
> > > > providing an ALLOC ioctl.
> > > >
> > > > Also, I've provided relatively simple system and cma heaps.
> > > >
> > > > I've booted and tested these patches with AOSP on the HiKey960
> > > > using the kernel tree here:
> > > >   https://git.linaro.org/people/john.stultz/android-dev.git/log/?h=dev/dma-buf-heap
> > > >
> > > > And the userspace changes here:
> > > >   https://android-review.googlesource.com/c/device/linaro/hikey/+/909436
> > > >
> > > > Compared to ION, this patchset is missing the system-contig,
> > > > carveout and chunk heaps, as I don't have a device that uses
> > > > those, so I'm unable to do much useful validation there.
> > > > Additionally we have no upstream users of chunk or carveout,
> > > > and the system-contig has been deprecated in the common/andoid-*
> > > > kernels, so this should be ok.
> > > >
> > > > I've also removed the stats accounting, since any such accounting
> > > > should be implemented by dma-buf core or the heaps themselves.
> > > >
> > > > Most of the changes in this revision are adddressing the more
> > > > concrete feedback from Christoph (many thanks!). Though I'm not
> > > > sure if some of the less specific feedback was completely resolved
> > > > in discussion last time around. Please let me know!
> > >
> > > It looks like most of the feedback has been taken care of. If there's
> > > no more objection to this series, I'd like to merge it in soon.
> > >
> > > If there are any more review comments, may I request you to please provide them?
> >
> > I tested these patches using our internal test suite with Arm,komeda
> > driver and the following node in dts
> >
> >         reserved-memory {
> >                 #address-cells = <0x2>;
> >                 #size-cells = <0x2>;
> >                 ranges;
> >
> >                 framebuffer@...00000 {
> >                         compatible = "shared-dma-pool";
> >                         linux,cma-default;
> >                         reg = <0x0 0x60000000 0x0 0x8000000>;
> >                 };
> >         }
> Apologies for the confusion, this dts node is irrelevant as our tests were using
> the cma heap (via /dev/dma_heap/reserved).
>
> That raises a question. How do we represent the reserved-memory nodes
> (as shown above) via the dma-buf heaps framework ?

(Apologies I didn't initially see this as you somehow left me off the
reply list)

So yea, as Brian mentioned, we'll generate a heap for each cma area.
So the above should generate a heap named "framebuffer".

For example, on HiKey960 the following patch adds (originally for ION,
but the same dt node will work for dmabuf heaps) the cma heap
"linux,cma"
  https://git.linaro.org/people/john.stultz/android-dev.git/commit/?h=dev/dma-buf-heap&id=00538fe70e17acf07fdcbc441816d91cdd227207

thanks
-john