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

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Message-ID: <fa063d1b-c23c-c29c-f9b4-c77be4626fd5@gmail.com>
Date:   Tue, 25 May 2021 08:25:36 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Maxime Ripard <maxime@...no.tech>,
        Jaroslav Kysela <perex@...ex.cz>,
        Mark Brown <broonie@...nel.org>,
        dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        Takashi Iwai <tiwai@...e.com>
Cc:     devicetree@...r.kernel.org,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>, linux-doc@...r.kernel.org,
        Eric Anholt <eric@...olt.net>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
        Maxime Ripard <mripard@...nel.org>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org,
        Daniel Vetter <daniel@...ll.ch>,
        linux-rpi-kernel@...ts.infradead.org,
        Jonathan Corbet <corbet@....net>,
        Rob Herring <robh+dt@...nel.org>,
        Dom Cobley <popcornmix@...il.com>
Subject: Re: [PATCH v2 12/12] ARM: dts: bcm2711: Tune DMA parameters for HDMI
 audio



On 5/25/2021 6:23 AM, Maxime Ripard wrote:
> From: Dom Cobley <popcornmix@...il.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@...il.com>
> Signed-off-by: Maxime Ripard <maxime@...no.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@...00700 {
>  			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