Hi Jassi, 2018-08-21 19:44 GMT+09:00 Jassi Brar <jaswinder.singh@xxxxxxxxxx>: > On 21 August 2018 at 15:17, Masahiro Yamada > <yamada.masahiro@xxxxxxxxxxxxx> wrote: >> (+CC Rob, DT, LKML) >> >> I forgot to CC this to DT community... >> >> >> 2018-08-21 18:30 GMT+09:00 Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>: >>> The MIO DMAC (Media IO DMA Controller) is used in UniPhier LD4, >>> Pro4, and sLD8 SoCs. >>> >>> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> >>> --- >>> >>> .../devicetree/bindings/dma/uniphier-mio-dmac.txt | 28 ++++++++++++++++++++++ >>> 1 file changed, 28 insertions(+) >>> create mode 100644 Documentation/devicetree/bindings/dma/uniphier-mio-dmac.txt >>> >>> diff --git a/Documentation/devicetree/bindings/dma/uniphier-mio-dmac.txt b/Documentation/devicetree/bindings/dma/uniphier-mio-dmac.txt >>> new file mode 100644 >>> index 0000000..a9e969e >>> --- /dev/null >>> +++ b/Documentation/devicetree/bindings/dma/uniphier-mio-dmac.txt >>> @@ -0,0 +1,28 @@ >>> +UniPhier Media IO DMA controller >>> + >>> +This works as an external DMA engine for SD/eMMC controllers etc. >>> +found in UniPhier LD4, Pro4, sLD8 SoCs. >>> + >>> +Required properties: >>> +- compatible: should be "socionext,uniphier-mio-dmac". >>> +- reg: offset and length of the register set for the device. >>> +- interrupts: a list of interrupt specifiers associated with the DMA channels. >>> +- clocks: a single clock specifier >>> +- #dma-cells: should be <1>. The single cell represents the channel number. >>> +- dma-channels: specify the number of the DMA channels. This should match to >>> + the number of tuples in the interrupts property. >>> + > Can we not infer the number of channels from interrupt tuples? After > all the driver assumes they are same. It would be possible to count the number of tuples in "interrupts". I know of_irq_count(), but I do not see any driver in drivers/dma/ that calls it. I guess the reason is that of_irq_count() is not exported, so tristate drivers like this cannot use it. I checked Documentation/devicetree/bindings/dma/, and some controllers specify _redundant_ dma-channels property. fsl-mxs-dma.txt renesas,rcar-dmac.txt renesas,usb-dmac.txt I also see counter-implementation. bcm2835-dma.c hard-codes the number of channels in the driver. tegra210-adma.c associates nr_channels with compatible string. I will wait for comments from the maintainers. If desired, I will export of_irq_count() and use it from my driver. Thanks. -- Best Regards Masahiro Yamada
