Re: [RFC v02 03/15] dmaengine: core: Introduce new, universal API to request a channel

Tony Lindgren
2015-11-30T15:51:42Z

Hi,

* Peter Ujfalusi <peter.ujfalusi-l0cyMroinI0@public.gmane.org> [151130 05:49]:
>
> For each dmaengine driver an array of DMA device, slave and the parameter
> for the filter function needs to be added:
>
> static struct dma_filter_map da830_edma_map[] = {
> DMA_FILTER_ENTRY("davinci-mcasp.0", "rx", EDMA_CTLR_CHAN(0, 0)),
> DMA_FILTER_ENTRY("davinci-mcasp.0", "tx", EDMA_CTLR_CHAN(0, 1)),
> DMA_FILTER_ENTRY("davinci-mcasp.1", "rx", EDMA_CTLR_CHAN(0, 2)),
> DMA_FILTER_ENTRY("davinci-mcasp.1", "tx", EDMA_CTLR_CHAN(0, 3)),
> DMA_FILTER_ENTRY("davinci-mcasp.2", "rx", EDMA_CTLR_CHAN(0, 4)),
> DMA_FILTER_ENTRY("davinci-mcasp.2", "tx", EDMA_CTLR_CHAN(0, 5)),
> DMA_FILTER_ENTRY("spi_davinci.0", "rx", EDMA_CTLR_CHAN(0, 14)),
> DMA_FILTER_ENTRY("spi_davinci.0", "tx", EDMA_CTLR_CHAN(0, 15)),
> DMA_FILTER_ENTRY("da830-mmc.0", "rx", EDMA_CTLR_CHAN(0, 16)),
> DMA_FILTER_ENTRY("da830-mmc.0", "tx", EDMA_CTLR_CHAN(0, 17)),
> DMA_FILTER_ENTRY("spi_davinci.1", "rx", EDMA_CTLR_CHAN(0, 18)),
> DMA_FILTER_ENTRY("spi_davinci.1", "tx", EDMA_CTLR_CHAN(0, 19)),
> };

FYI, if the EDMA_CTRL_CHAN above is just the evtmux registers, those
can be handled with the pinctrl framework. It seems that would allow
leaving out some of the built-in look up data, and have the mux parts
handled by a proper device driver. Below is a sample from the dm81xx
platform for reference.

SoC dtsi file:

evtmux: pinmux@f90 {
compatible = "pinctrl-single";
reg = <0xf90 0x40>;
#address-cells = <1>;
#size-cells = <0>;
pinctrl-single,register-width = <8>;
pinctrl-single,function-mask = <0x1f>;
};

Board specific dts file:

&evtmux {
sd2_edma_pins: pinmux_sd2_edma_pins {
pinctrl-single,pins = <
8 1 /* use SDTXEVT1 for EDMA instead of MCASP0TX */
9 2 /* use SDRXEVT1 for EDMA instead of MCASP0RX */
>;
};
};

Dynamic muxing of these channels can be done too using the pinctrl
framework named modes, but probably is not a good idea in the case of
SD card and MaASP in case something goes wrong :)

Regards,

Tony
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