Re: [EXT] Re: Enforce USB DMA allocations to specific range

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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http://daringfireball.net/2007/07/on_top

On Thu, Feb 11, 2021 at 08:38:40AM +0000, Noam Liron wrote:
> Hi Greg,
> 
> I am writing you again on the below subject, as I would like to get a
> "high level" opinion, and you are probably the most experienced ...

I am not a DMA expert at all, why not ask the dma developers instead?

> As I wrote below, I cannot rely on the DMA mask, as some USB
> allocation are not affected by it.

Why "some" and not "others"?  Perhaps you need to fix your platform code
to prevent that from happening instead?  Why is USB unique here?

> I thought of using private DMA pool that will be allocated where I
> need it (at the start of physical memory). However, this means adding
> specific ASIC code, which is less elegant.
> Do you think that's the right way?

I do not know your platform, only you do.

But I do think you should not be doing new development on 4.14, as that
is a very old and obsolete kernel and the dma code in the kernel has
changed a lot since 2017.

good luck!

greg k-h