linux-kernel - Re: [PATCH] ARM: dts: bcm283x: Unify CMA configuration

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Date:   Fri, 10 Jan 2020 17:37:25 +0000
From:   Phil Elwell <phil@...pberrypi.org>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Stefan Wahren <wahrenst@....net>
Cc:     devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: bcm283x: Unify CMA configuration

Hi Nicolas,

On 10/01/2020 17:29, Nicolas Saenz Julienne wrote:
> With the introduction of the Raspberry Pi 4 we were forced to explicitly
> configure CMA's location, since arm64 defaults it into the ZONE_DMA32
> memory area, which is not good enough to perform DMA operations on that
> device. To bypass this limitation a dedicated CMA DT node was created,
> explicitly indicating the acceptable memory range and size.
> 
> That said, compatibility between boards is a must on the Raspberry Pi
> ecosystem so this creates a common CMA DT node so as for DT overlays to
> be able to update CMA's properties regardless of the board being used.
> 
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> ---
> 
> If this doesn't make it into v5.5 I'd be tempted to add:
> Fixes: d98a8dbdaec6 ("ARM: dts: bcm2711: force CMA into first GB of memory")
> 
>   arch/arm/boot/dts/bcm2711.dtsi | 33 +++++++++++++--------------------
>   arch/arm/boot/dts/bcm283x.dtsi | 13 +++++++++++++
>   2 files changed, 26 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/arm/boot/dts/bcm2711.dtsi b/arch/arm/boot/dts/bcm2711.dtsi
> index 8687534d4528..c8e4041308e0 100644
> --- a/arch/arm/boot/dts/bcm2711.dtsi
> +++ b/arch/arm/boot/dts/bcm2711.dtsi
> @@ -12,26 +12,6 @@ / {
>   
>   	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 BCM2711 as some 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:
> @@ -869,6 +849,19 @@ pin-rts {
>   	};
>   };
>   
> +&rmem {
> +	#address-cells = <2>;
> +};
> +
> +&cma {
> +	/*
> +	 * arm64 reserves the CMA by default somewhere in ZONE_DMA32,
> +	 * that's not good enough for the BCM2711 as some devices can
> +	 * only address the lower 1G of memory (ZONE_DMA).
> +	 */
> +	alloc-ranges = <0x0 0x00000000 0x40000000>;
> +};
> +
>   &i2c0 {
>   	compatible = "brcm,bcm2711-i2c", "brcm,bcm2835-i2c";
>   	interrupts = <GIC_SPI 117 IRQ_TYPE_LEVEL_HIGH>;
> diff --git a/arch/arm/boot/dts/bcm283x.dtsi b/arch/arm/boot/dts/bcm283x.dtsi
> index 839491628e87..6128baed83c2 100644
> --- a/arch/arm/boot/dts/bcm283x.dtsi
> +++ b/arch/arm/boot/dts/bcm283x.dtsi
> @@ -30,6 +30,19 @@ chosen {
>   		stdout-path = "serial0:115200n8";
>   	};
>   
> +	rmem: reserved-memory {
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +		ranges;
> +
> +		cma: linux,cma {
> +			compatible = "shared-dma-pool";
> +			size = <0x4000000>; /* 64MB */
> +			reusable;
> +			linux,cma-default;
> +		};
> +	};
> +
>   	thermal-zones {
>   		cpu_thermal: cpu-thermal {
>   			polling-delay-passive = <0>;
> 

For what it's worth,

Reviewed-by: Phil Elwell <phil@...pberrypi.org>

Phil