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From:   Baolin Wang <baolin.wang@linaro.org>
Date:   Tue, 12 Feb 2019 16:24:51 +0800
Message-ID: <CAMz4kuLEut0LqZ4bSAGJDufE8xHr6DgZ3Z1RCLQ10q_k6MUesw@mail.gmail.com>
Subject: Re: [PATCH 1/3] dt-bindings: dmaengine: Add one new cell to present
 hardware slave id
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Vinod Koul <vkoul@kernel.org>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Olof Johansson <olof@lixom.net>,
        Orson Zhai <orsonzhai@gmail.com>,
        Lyra Zhang <zhang.lyra@gmail.com>,
        Dan Williams <dan.j.williams@intel.com>,
        DTML <devicetree@vger.kernel.org>, arm-soc <arm@kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        dmaengine@vger.kernel.org, eric.long@unisoc.com,
        Mark Brown <broonie@kernel.org>
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Hi Arnd,

On Fri, 1 Feb 2019 at 19:53, Baolin Wang <baolin.wang@linaro.org> wrote:
>
> Hi Arnd,
> On Thu, 31 Jan 2019 at 00:52, Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > On Tue, Jan 22, 2019 at 2:21 PM Baolin Wang <baolin.wang@linaro.org> wrote:
> > >
> > > The DMA engine clients can trigger DMA engine automatically by setting
> > > the corresponding hardware slave id for the DMA engine. Thus add one
> > > cell to present the hardware slave id for DMA clients.
> > >
> > > Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> > > ---
> > >  Documentation/devicetree/bindings/dma/sprd-dma.txt |   12 +++++++-----
> > >  1 file changed, 7 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/dma/sprd-dma.txt b/Documentation/devicetree/bindings/dma/sprd-dma.txt
> > > index 7a10fea..7812cf0 100644
> > > --- a/Documentation/devicetree/bindings/dma/sprd-dma.txt
> > > +++ b/Documentation/devicetree/bindings/dma/sprd-dma.txt
> > > @@ -6,8 +6,8 @@ Required properties:
> > >  - compatible: Should be "sprd,sc9860-dma".
> > >  - reg: Should contain DMA registers location and length.
> > >  - interrupts: Should contain one interrupt shared by all channel.
> > > -- #dma-cells: must be <1>. Used to represent the number of integer
> > > -       cells in the dmas property of client device.
> > > +- #dma-cells: must be <2>. Used to represent the channel id and slave id
> > > +       of integer cells in the dmas property of client device.
> > >  - #dma-channels : Number of DMA channels supported. Should be 32.
> > >  - clock-names: Should contain the clock of the DMA controller.
> > >  - clocks: Should contain a clock specifier for each entry in clock-names.
> > > @@ -28,14 +28,16 @@ apdma: dma-controller@20100000 {
> > >
> > >  Client:
> > >  DMA clients connected to the Spreadtrum DMA controller must use the format
> > > -described in the dma.txt file, using a two-cell specifier for each channel.
> > > -The two cells in order are:
> > > +described in the dma.txt file, using a three-cell specifier for each channel.
> > > +The three cells in order are:
> > >  1. A phandle pointing to the DMA controller.
> > >  2. The channel id.
> > > +3. The hardware slave id which is used for clients to trigger DMA engine
> > > +automatically.
> >
> > I notice that this is an incompatible binding change. Is that necessary?
> > If the current code works, I'd suggest allowing both #dma-cells=<2>
> > and <3>, and then implementing both in the driver.
>
> Yes, this is necessary.
>
> Yes, current code can work, but the problem is that the DMA clients
> must add one property (something like "sprd,slave-id") to specify the
> slave id. So considering this, we want to change the dma-cells to 2,
> including dma channel and dma slave id, which can avoid introducing
> some similar properties for DMA clients.
>
> Now there are no DMA clients in mainline for Spreadtrum platform, and
> we want to upstream our first DMA clients: SPI controller. So no other
> drivers need to change when we changing dma cells. Thanks.

Do you have any other concerns about this patch set? If not, I think
Vinod can apply this patch set. Thanks.

-- 
Baolin Wang
Best Regards