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

[Jaskaran Singh]

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@xxxxxxxxxxxxx/
>>  ?
>> 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@xxxxxxxxxxxx/;

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
>>
>>
>>