linux-kernel - Re: [PATCH] arm64: dts: qcom: sdm845-db845c: Mark cont splash memory region as reserved

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Message-ID: <39751511-3f06-7c39-9c21-208d4c272113@linaro.org>
Date:   Tue, 31 Jan 2023 10:54:47 +0000
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Amit Pundir <amit.pundir@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Caleb Connolly <caleb.connolly@...aro.org>
Cc:     linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dt <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: sdm845-db845c: Mark cont splash memory
 region as reserved

On 24/01/2023 18:28, Amit Pundir wrote:
> Put cont splash memory region under the reserved-memory
> as confirmed by the downstream code as well.
> 
> Signed-off-by: Amit Pundir <amit.pundir@...aro.org>
> ---
>   arch/arm64/boot/dts/qcom/sdm845-db845c.dts | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> index f41c6d600ea8..2ae59432cbda 100644
> --- a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> +++ b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> @@ -100,6 +100,14 @@ hdmi_con: endpoint {
>   		};
>   	};
>   
> +	reserved-memory {
> +		/* Cont splash region set up by the bootloader */
> +		cont_splash_mem: framebuffer@...00000 {
> +			reg = <0x0 0x9d400000 0x0 0x2400000>;
> +			no-map;
> +		};
> +	};
> +
>   	lt9611_1v8: lt9611-vdd18-regulator {
>   		compatible = "regulator-fixed";
>   		regulator-name = "LT9611_1V8";

Doesn't this mean we loose 0x2400000 of DRAM for all rb3 platforms 
though ? About what 37 megabytes.. ?

IMO it would be better to have a bootloader that cares about continuous 
splash to apply a dtb overlay or simply to add a separate dts 
sdm845-db845c-continuous-spash.dts.

---
bod