linux-kernel - Re: [PATCH v3 11/12] arm64: dts: imx8q: add linux,cma node for imx8qm-mek and imx8qxp-mek

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Message-ID: <20250327190037.GB22659@pendragon.ideasonboard.com>
Date: Thu, 27 Mar 2025 21:00:37 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Frank Li <Frank.Li@....com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Dong Aisheng <aisheng.dong@....com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Rui Miguel Silva <rmfrfs@...il.com>,
	Martin Kepplinger <martink@...teo.de>,
	Purism Kernel Team <kernel@...i.sm>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
	Robert Chiras <robert.chiras@....com>,
	"Guoniu.zhou" <guoniu.zhou@....com>
Subject: Re: [PATCH v3 11/12] arm64: dts: imx8q: add linux,cma node for
 imx8qm-mek and imx8qxp-mek

Hi Frank,

Thank you for the patch.

On Mon, Feb 10, 2025 at 03:59:30PM -0500, Frank Li wrote:
> Add linux,cma node because some devices, such as camera, need big continue
> physical memory.
> 
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
> change from v1 to v3
> - none
> ---
>  arch/arm64/boot/dts/freescale/imx8qm-mek.dts  | 9 +++++++++
>  arch/arm64/boot/dts/freescale/imx8qxp-mek.dts | 8 ++++++++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8qm-mek.dts b/arch/arm64/boot/dts/freescale/imx8qm-mek.dts
> index 50fd3370f7dce..61ef00f4259e1 100644
> --- a/arch/arm64/boot/dts/freescale/imx8qm-mek.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8qm-mek.dts
> @@ -113,6 +113,15 @@ dsp_vdev0buffer: memory@...00000 {
>  			reg = <0 0x94300000 0 0x100000>;
>  			no-map;
>  		};
> +
> +		/* global autoconfigured region for contiguous allocations */
> +		linux,cma {
> +			compatible = "shared-dma-pool";
> +			alloc-ranges = <0 0xc0000000 0 0x3c000000>;
> +			size = <0 0x3c000000>;
> +			linux,cma-default;
> +			reusable;
> +		};

This is system memory. Why is it reserved here, hardcoding a specific
use case in a board DT, instead of specifying an overall CMA size in the
kernel configuration or through the kernel command line ?

>  	};
>  
>  	lvds_backlight0: backlight-lvds0 {
> diff --git a/arch/arm64/boot/dts/freescale/imx8qxp-mek.dts b/arch/arm64/boot/dts/freescale/imx8qxp-mek.dts
> index be79c793213a5..89c6516c5ba90 100644
> --- a/arch/arm64/boot/dts/freescale/imx8qxp-mek.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8qxp-mek.dts
> @@ -56,6 +56,14 @@ dsp_vdev0buffer: memory@...00000 {
>  			reg = <0 0x94300000 0 0x100000>;
>  			no-map;
>  		};
> +
> +		linux,cma {
> +			compatible = "shared-dma-pool";
> +			alloc-ranges = <0 0xc0000000 0 0x3c000000>;
> +			size = <0 0x3c000000>;
> +			linux,cma-default;
> +			reusable;
> +		};
>  	};
>  
>  	reg_usdhc2_vmmc: usdhc2-vmmc {

-- 
Regards,

Laurent Pinchart