linux-kernel - Re: [PATCH 8/9] dt-bindings: reserved-memory: MediaTek: Add reserved memory for SVP

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Message-ID: <a83b00c4-a33a-4687-b024-173c6c5a66a0@quicinc.com>
Date:   Wed, 1 Nov 2023 11:20:45 +0530
From:   Jaskaran Singh <quic_jasksing@...cinc.com>
To:     Yong Wu (吴勇) <Yong.Wu@...iatek.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "quic_vjitta@...cinc.com" <quic_vjitta@...cinc.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "sumit.semwal@...aro.org" <sumit.semwal@...aro.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "jstultz@...gle.com" <jstultz@...gle.com>,
        "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Jianjiao Zeng (曾健姣) 
        <Jianjiao.Zeng@...iatek.com>,
        Kuohong Wang (王國鴻) 
        <kuohong.wang@...iatek.com>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "Brian.Starkey@....com" <Brian.Starkey@....com>,
        "benjamin.gaignard@...labora.com" <benjamin.gaignard@...labora.com>,
        "tjmercier@...gle.com" <tjmercier@...gle.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH 8/9] dt-bindings: reserved-memory: MediaTek: Add reserved
 memory for SVP

On 10/20/2023 3:20 PM, Yong Wu (吴勇) wrote:
> On Thu, 2023-10-19 at 10:16 +0530, Vijayanand Jitta wrote:
>>  	 
>> Instead of having a vendor specific binding for cma area, How about
>> retrieving
>>
> https://lore.kernel.org/lkml/1594948208-4739-1-git-send-email-hayashi.kunihiko@socionext.com/
>>  ?
>> dma_heap_add_cma can just associate cma region and create a heap. So,
>> we can reuse cma heap
>> code for allocation instead of replicating that code here.
>>
> 
> Thanks for the reference. I guess we can't use it. There are two
> reasons:
>   
> a) The secure heap driver is a pure software driver and we have no
> device for it, therefore we cannot call dma_heap_add_cma.
>   

Hi Yong,

We're considering using struct cma as the function argument to
dma_heap_add_cma() rather than struct device. Would this help
resolve the problem of usage with dma_heap_add_cma()?

> b) The CMA area here is dynamic for SVP. Normally this CMA can be used
> in the kernel. In the SVP case we use cma_alloc to get it and pass the
> entire CMA physical start address and size into TEE to protect the CMA
> region. The original CMA heap cannot help with the TEE part.
>

Referring the conversation at
https://lore.kernel.org/lkml/7a2995de23c24ef22c071c6976c02b97e9b50126.camel@mediatek.com/;

since we're considering abstracting secure mem ops, would it make sense
to use the default CMA heap ops (cma_heap_ops), allocate buffers from it
and secure each allocated buffer?

Thanks,
Jaskaran.

> Thanks.
> 
>> Thanks,
>> Vijay
>>
>>
>>