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

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Message-ID: <8508e3d5-7468-0b2f-5a43-7c439ecf2d8b@linaro.org>
Date:   Tue, 31 Jan 2023 15:33:19 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc:     Amit Pundir <amit.pundir@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Caleb Connolly <caleb.connolly@...aro.org>,
        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 31/01/2023 14:45, Konrad Dybcio wrote:
> 
> 
> On 31.01.2023 12:06, Dmitry Baryshkov wrote:
>> On Tue, 31 Jan 2023 at 12:54, Bryan O'Donoghue
>> <bryan.odonoghue@...aro.org> wrote:
>>>
>>> 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.. ?
>>
>> I think this memory is further used for display memory allocation. So
>> we are not loosing it, but dedicating it to the framebuffer memory.
> Not exactly, to do so, you'd have to use the memory-region property
> with mdss, which nobody does. Otherwise it's just a hole for Linux.

Then maybe it's time to start using that property?

> 
> Konrad
>>
>>

-- 
With best wishes
Dmitry