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

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Message-ID: <76311e72-0e18-d6b7-6dfc-a312e930e095@linaro.org>
Date:   Thu, 9 Feb 2023 13:32:30 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     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 9.02.2023 13:22, Bryan O'Donoghue wrote:
> On 09/02/2023 12:11, Bryan O'Donoghue wrote:
>>> If the bootloader splash is enabled then this memory is used until the
>>> DPU driver instructs MDP5 pipes to suck data from a newly assigned address,
>>> so there's a short window where it is.
>>
>> It seems a shame to reserve 30 something megabytes of memory for continuous splash unless we are actually using it is my point.
>>
>> If I'm running headless its just wasted memory.
> 
> Couldn't we
> 
> 1. Find reserved continuous splash memory
> 2. Fee it in the MDP when we make the transition
> 
> It must be possible
I suppose we could mark it as shared-dma-pool, pass it to
MDSS, reserve it from there (by occupying the whole thing)
and either use it or free it before jumping to the newly
allocated region.

The MDSS driver can already accept it through memory-region = <>
IIRC, but *nobody* uses that, so I'm not sure it even still works..

Konrad
> 
> ---
> bod