linux-kernel - Re: [PATCH v2 1/2] ARM: dts: bcm2711: force CMA into first GB of memory

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Date:   Thu, 7 Nov 2019 07:23:15 +0100
From:   Stefan Wahren <wahrenst@....net>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        catalin.marinas@....com, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Eric Anholt <eric@...olt.net>
Cc:     linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] ARM: dts: bcm2711: force CMA into first GB of
 memory

Hi Nicolas,

Am 06.11.19 um 10:59 schrieb Nicolas Saenz Julienne:
> arm64 places the CMA in ZONE_DMA32, which is not good enough for the
> Raspberry Pi 4 since it contains peripherals that can only address the
> first GB of memory. Explicitly place the CMA into that area.
>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
>
> ---
>
> Changes since v1:
>   - Move into bcm2711.dtsi
>
>  arch/arm/boot/dts/bcm2711.dtsi | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/arch/arm/boot/dts/bcm2711.dtsi b/arch/arm/boot/dts/bcm2711.dtsi
> index 1f3acd3363ea..6000a01652fa 100644
> --- a/arch/arm/boot/dts/bcm2711.dtsi
> +++ b/arch/arm/boot/dts/bcm2711.dtsi
> @@ -12,6 +12,26 @@
>
>  	interrupt-parent = <&gicv2>;
>
> +	reserved-memory {
> +		#address-cells = <2>;
> +		#size-cells = <1>;
> +		ranges;
> +
> +		/*
> +		 * arm64 reserves the CMA by default somewhere in ZONE_DMA32,
> +		 * that's not good enough for the Raspberry Pi 4 as some

sorry for the nitpicking but i hope the Raspberry Pi 4 B wont be the
only user of BCM2711.

So please s/Raspberry Pi 4/BCM2711/

Beside that:

Acked-by: Stefan Wahren <wahrenst@....net>

> +		 * devices can only address the lower 1G of memory (ZONE_DMA).
> +		 */
> +		linux,cma {
> +			compatible = "shared-dma-pool";
> +			size = <0x2000000>; /* 32MB */
> +			alloc-ranges = <0x0 0x00000000 0x40000000>;
> +			reusable;
> +			linux,cma-default;
> +		};
> +	};
> +
> +
>  	soc {
>  		/*
>  		 * Defined ranges: