On 23 August 2018 at 10:48, Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> wrote: > 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 am not sure "because others are doing it" is a good reason to introduce redundancy. > 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. > If you don't want to leave too much footprint, you could do count = 0; while (of_irq_parse_one(dev, count, &irq) == 0) count++ of_irq_parse_one() is already exported. A good side-effect is you wouldn't have to hardcode the count in the driver (like bcm and tegra examples you quote). Having said that, I wouldn't lose sleep over it. So .... Cheers!
