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

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Date:   Mon, 6 Nov 2023 05:56:03 +0000
From:   Yong Wu (吴勇) <Yong.Wu@...iatek.com>
To:     "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "quic_vjitta@...cinc.com" <quic_vjitta@...cinc.com>,
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        "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>,
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        Jianjiao Zeng (曾健姣) 
        <Jianjiao.Zeng@...iatek.com>,
        Kuohong Wang (王國鴻) 
        <kuohong.wang@...iatek.com>,
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        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH 8/9] dt-bindings: reserved-memory: MediaTek: Add reserved
 memory for SVP

On Wed, 2023-11-01 at 11:20 +0530, Jaskaran Singh wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  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()?

Yes. If we use "struct cma", I guess it works.

> 
> > 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?

Then it looks you also need tee operation like tee_client_open_session
and tee_client_invoke_func, right?

It seems we also need change a bit for "cma_heap_allocate" to allow cma
support operations from secure heap.

I will send a v2 to move the discussion forward. The v2 is based on our
case, It won't include the cma part.

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