linux-kernel - Re: your mail

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Message-ID: <20140225150125.GC23136@mudshark.cambridge.arm.com>
Date:	Tue, 25 Feb 2014 15:01:25 +0000
From:	Will Deacon <will.deacon@....com>
To:	srikanth TS <srikantht.shivanand@...il.com>
Cc:	"ts.srikanth@...sung.com" <ts.srikanth@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"sungjinn.chung@...sung.com" <sungjinn.chung@...sung.com>
Subject: Re: your mail

On Tue, Feb 25, 2014 at 11:20:11AM +0000, srikanth TS wrote:
> 
> On Feb 25, 2014 2:28 AM, "Will Deacon" <will.deacon@....com<mailto:will.deacon@....com>> wrote:
> >
> > On Mon, Feb 24, 2014 at 03:12:21PM +0000, srikanth TS wrote:
> > > Hi Will Deacon,
> >
> > Hello,
> >
> > > Currently SMMU driver expecting all stream ID used by respective master
> > > should be defined in the DT.
> > >
> > > We want to know how to handle in the case of virtual functions dynamically
> > > created and destroyed.
> > >
> > > Is PCI driver responsible for creating stream ID respective BDand
> > > requesting SMMU to add to the mapping table[stream Id to context mapping
> > > table]?
> > >
> > > Or is there any right way of doing it?
> >
> > Correct, the driver currently doesn't support dynamic mappings (mainly
> > because I didn't want to try and invent something that I couldn't test).
> >
> > There are a couple of ways to solve this:
> >
> >   (1) Add a way for a PCI RC to dynamically allocate StreamIDs on an SMMU
> >       within a fixed range. That would probably need some code in the bus
> >       layer, so that a bus notifier can kick and call back to the relevant
> >       SMMU.
> 
> I think first way of solving seems to be better, because we don't know how many
> 
> VF are used and i feel its not good idea to keep whole list of streamID [which is
> 
> equal to max num vf] in DT. Again in this method we need to generate the stream ID
> 
> dynamically whenever VF is added in pci iov driver side. And then pass that
> 
> stream ID to SMMU.
> 
> Is it ok this way?  Or you prefer 2nd way which is simpler.

I'm happy either way, but I'd need to see some patches before I can merge
anything ;)

Will
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