linux-kernel - Re: [PATCH 3/4] dt-bindings: spi: Add the DMA properties for the SPI dma mode

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Date:   Tue, 22 Jan 2019 10:22:58 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Orson Zhai <orsonzhai@...il.com>,
        Lyra Zhang <zhang.lyra@...il.com>, lanqing.liu@...soc.com,
        linux-spi <linux-spi@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] dt-bindings: spi: Add the DMA properties for the SPI
 dma mode

On Mon, 21 Jan 2019 at 21:53, Rob Herring <robh+dt@...nel.org> wrote:
>
> On Tue, Jan 15, 2019 at 7:47 AM Baolin Wang <baolin.wang@...aro.org> wrote:
> >
> > From: Lanqing Liu <lanqing.liu@...eadtrum.com>
>
> The email address should be updated with unisoc.com.

Sure.

>
> > Add the DMA properties for the SPI dma mode.
> >
> > Signed-off-by: Lanqing Liu <lanqing.liu@...eadtrum.com>
> > Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> > ---
> >  Documentation/devicetree/bindings/spi/spi-sprd.txt |    9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/spi/spi-sprd.txt b/Documentation/devicetree/bindings/spi/spi-sprd.txt
> > index bad211a..01ef53f 100644
> > --- a/Documentation/devicetree/bindings/spi/spi-sprd.txt
> > +++ b/Documentation/devicetree/bindings/spi/spi-sprd.txt
> > @@ -14,6 +14,12 @@ Required properties:
> >         address on the SPI bus. Should be set to 1.
> >  - #size-cells: Should be set to 0.
> >
> > +Optional properties:
> > +dma-names: Should contain names of the SPI used DMA channel.
> > +dmas: Should contain DMA channels which the SPI used sorted in the
> > +       same order as the dma-names property.
> > +sprd,dma-slave-ids: Should contain the DMA number that the SPI hardware required.
> > +
> >  Example:
> >  spi0: spi@...00000{
> >         compatible = "sprd,sc9860-spi";
> > @@ -21,6 +27,9 @@ spi0: spi@...00000{
> >         interrupts = <GIC_SPI 7 IRQ_TYPE_LEVEL_HIGH>;
> >         clock-names = "spi", "source","enable";
> >         clocks = <&clk_spi0>, <&ext_26m>, <&clk_ap_apb_gates 5>;
> > +       dma-names = "rx_chn", "tx_chn";
> > +       dmas = <&apdma 11>, <&apdma 12>;
> > +       sprd,dma-slave-ids = <11 12>;
>
> When would this be different values from what's in 'dmas'?

Slave id is not always same with the DMA channel number in 'dmas', and
it is just coincident for SPI driver. Moreover for different SoC , the
slave ids for DMA engine consumers are not same. So we need one
property to specify the slave id for the consumers to trigger DMA
transfer.

-- 
Baolin Wang
Best Regards