linux-kernel - Re: [PATCH v3] arm64: dts: qcom: sdm845-db845c: Mark cont splash memory region as reserved

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Date:   Mon, 10 Jul 2023 16:48:04 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...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>,
        Conor Dooley <conor+dt@...nel.org>,
        Caleb Connolly <caleb.connolly@...aro.org>,
        Bryan Donoghue <bryan.odonoghue@...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 v3] arm64: dts: qcom: sdm845-db845c: Mark cont splash
 memory region as reserved

On 16/06/2023 08:51, Amit Pundir wrote:
> Adding a reserved memory region for the framebuffer memory
> (the splash memory region set up by the bootloader).
> 
> Signed-off-by: Amit Pundir <amit.pundir@...aro.org>
> ---
> v3: Point this reserved region to MDSS.
> 
> v2: Updated commit message.
> 
> There was some dicussion on v1 but it didn't go anywhere,
> https://lore.kernel.org/linux-kernel/20230124182857.1524912-1-amit.pundir@linaro.org/T/#u.
> The general consensus is that this memory should be freed and be
> made resuable but that (releasing this piece of memory) has been
> tried before and it is not trivial to return the reserved memory
> node to the system RAM pool in this case.
> 
>  arch/arm64/boot/dts/qcom/sdm845-db845c.dts | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> index df2fde9063dc..503136eb9c06 100644
> --- a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> +++ b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> @@ -101,6 +101,14 @@ 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";
> @@ -517,6 +525,7 @@ &i2c14 {
>  };
>  
>  &mdss {
> +	memory-region = <&cont_splash_mem>;

Just to be sure: does this pass the dtbs_check testing? I would say it
does not and wasn't tested :(

Best regards,
Krzysztof