Re: your mail

Will Deacon
2014-02-24T17:29:04Z

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.

(2) Describe the RID -> SID mapping in the device-tree. We probably want
to avoid an enormous table, so this would only work for simple `SID =
RID + offset' or 'SID = RID & mask' cases.

How do your IDs map to each other?

Will