linux-kernel - Re: [PATCH] arm64: dts: qcom: sc8280xp: Define CMA region for CRD and X13s

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Date:   Fri, 13 Jan 2023 15:17:05 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH] arm64: dts: qcom: sc8280xp: Define CMA region for CRD and
 X13s



On 13.01.2023 05:10, Bjorn Andersson wrote:
> Booting the CRD needs roughly 64MB CMA, rather than relying on people
> adding boot parameters etc define a region for this, to remove the
> allocation errors from e.g. NVME.
> 
> While fixing the CRD define the same region for the X13s.
> 
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> ---
So, to reiterate, the NVMe needs ~64M of contiguous RAM for
$reasons and without this patch, it is not guaranteed that
it can always find such a block which causes issues and
adding a CMA region resolves that, is that correct?

Konrad
>  arch/arm64/boot/dts/qcom/sc8280xp-crd.dts                | 9 +++++++++
>  .../boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts      | 9 +++++++++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sc8280xp-crd.dts b/arch/arm64/boot/dts/qcom/sc8280xp-crd.dts
> index b29c02307839..e30a37c73b90 100644
> --- a/arch/arm64/boot/dts/qcom/sc8280xp-crd.dts
> +++ b/arch/arm64/boot/dts/qcom/sc8280xp-crd.dts
> @@ -128,6 +128,15 @@ vreg_wwan: regulator-wwan {
>  
>  		regulator-boot-on;
>  	};
> +
> +	reserved-memory {
> +		linux,cma {
> +			compatible = "shared-dma-pool";
> +			size = <0x0 0x8000000>;
> +			reusable;
> +			linux,cma-default;
> +		};
> +	};
>  };
>  
>  &apps_rsc {
> diff --git a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
> index 78e61a8184c5..5bfd1f0b2a24 100644
> --- a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
> +++ b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
> @@ -153,6 +153,15 @@ vreg_wwan: regulator-wwan {
>  		regulator-boot-on;
>  	};
>  
> +	reserved-memory {
> +		linux,cma {
> +			compatible = "shared-dma-pool";
> +			size = <0x0 0x8000000>;
> +			reusable;
> +			linux,cma-default;
> +		};
> +	};
> +
>  	thermal-zones {
>  		skin-temp-thermal {
>  			polling-delay-passive = <250>;