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

[Florian Fainelli]

On 5/25/2021 6:23 AM, Maxime Ripard wrote:
> From: Dom Cobley <popcornmix@xxxxxxxxx>
> 
> 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@xxxxxxxxx>
> Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>
> ---
>  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