linux-kernel - Re: [PATCH v2 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition

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Message-ID: <3049147914a4a04a095a3f3bd74a7c7ad4d961ad.camel@gmail.com>
Date:   Wed, 01 Jul 2020 21:54:41 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/6] powerpc/pseries/iommu: Make use of DDW even if
 it does not map the partition

On Thu, 2020-07-02 at 10:31 +1000, Alexey Kardashevskiy wrote:
> > In fact, there is a lot of places in this file where it's called direct
> > window. Should I replace everything?
> > Should it be in a separated patch?
> 
> If it looks simple and you write a nice commit log explaining all that
> and why you are not reusing the existing ibm,dma-window property 
> for that - sure, do it :)

Nice, I will do that :)

> (to provide a clue what "reset" will reset to? is there any other
> reason?)

That's the main reason here. 

The way I perceive this, ibm,dma-window should only point to the
default DMA window, which is guaranteed to always be the same, even if
it's destroyed and re-created. So there I see no point destroying /
overwriting it.

On the other hand, I also thought about using a new node name for this
window, but it would be very troublesome and I could see no real gain.

Thanks !