Without this, the driver for the BCM2835 SPI controller uses interrupt mode instead of DMA mode, incurring a significant performance penalty. The Foundation's device tree has had these attributes for years, but for some reason they were never upstreamed. They were originally contributed by Noralf Trønnes and Martin Sperl: https://github.com/raspberrypi/linux/commit/25f3e064afc8 https://github.com/raspberrypi/linux/commit/e0edb52b47e6 The DREQ numbers 6 and 7 are documented in section 4.2.1.3 of: https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf Tested-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> Cc: Martin Sperl <kernel@xxxxxxxxxxxxxxxx> Cc: Noralf Trønnes <noralf@xxxxxxxxxxx> --- arch/arm/boot/dts/bcm283x.dtsi | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/arm/boot/dts/bcm283x.dtsi b/arch/arm/boot/dts/bcm283x.dtsi index 9777644..4b21ddb 100644 --- a/arch/arm/boot/dts/bcm283x.dtsi +++ b/arch/arm/boot/dts/bcm283x.dtsi @@ -431,6 +431,8 @@ reg = <0x7e204000 0x1000>; interrupts = <2 22>; clocks = <&clocks BCM2835_CLOCK_VPU>; + dmas = <&dma 6>, <&dma 7>; + dma-names = "tx", "rx"; #address-cells = <1>; #size-cells = <0>; status = "disabled"; -- 2.20.1
