Re: [PATCH v2 12/12] ARM: dts: bcm2711: Tune DMA parameters for HDMI audio

Florian Fainelli
2021-05-25T15:25:50Z

On 5/25/2021 6:23 AM, Maxime Ripard wrote:
> From: Dom Cobley <popcornmix@gmail.com>
>
> Enable NO_WAIT_RESP, DMA_WIDE_SOURCE, DMA_WIDE_DEST, and bump the DMA
> panic and AXI priorities to avoid any DMA transfer error with HBR audio
> (8 channel, 192Hz).
>
> Signed-off-by: Dom Cobley <popcornmix@gmail.com>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> ---
> arch/arm/boot/dts/bcm2711.dtsi | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/boot/dts/bcm2711.dtsi b/arch/arm/boot/dts/bcm2711.dtsi
> index 720beec54d61..9d1dde973680 100644
> --- a/arch/arm/boot/dts/bcm2711.dtsi
> +++ b/arch/arm/boot/dts/bcm2711.dtsi
> @@ -344,7 +344,7 @@ hdmi0: hdmi@7ef00700 {
> interrupt-names = "cec-tx", "cec-rx", "cec-low",
> "wakeup", "hpd-connected", "hpd-removed";
> ddc = <&ddc0>;
> - dmas = <&dma 10>;
> + dmas = <&dma (10 | (1 << 27) | (1 << 24)| (15 << 20) | (10 << 16))>;

This uses DT as a configuration language rather than a description here,
but this is most certainly an established practice that the bcm283-dma.c
supports, with no validation of the various arguments.. great.

Is there at least an option to move the meaning of this bitfields into
include/dt-bindings/dma/bcm2835-dma.h or something like that?
--
Florian