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

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Date:   Tue, 31 Jan 2023 13:45:12 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...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 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.

Konrad
> 
>