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Re: [Qemu-devel] [RFC] QOMification of AXI stream
From: |
Edgar E. Iglesias |
Subject: |
Re: [Qemu-devel] [RFC] QOMification of AXI stream |
Date: |
Mon, 11 Jun 2012 17:56:28 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Jun 11, 2012 at 10:03:56AM -0500, Anthony Liguori wrote:
> On 06/11/2012 09:53 AM, Peter Maydell wrote:
> >On 11 June 2012 15:38, Edgar E. Iglesias<address@hidden> wrote:
> >>On Mon, Jun 11, 2012 at 02:39:56PM +0100, Peter Maydell wrote:
> >>>Ideally the interface used by DMA controllers should be identical to
> >>>the interface used by CPUs to talk to the rest of the system: it's
> >>>exactly the same bus interface in hardware, after all.
> >>
> >>I thought we were talking about the interface between the DMA ctrl
> >>and the I/O (devices). Not between the DMA and the "memory" bus system.
> >
> >In hardware (at least for AXI) they're the same thing. A DMA
> >controller is a bus master, just like a CPU. They don't care
> >whether the slave is RAM or a device, they're just issuing
> >memory transactions to addresses.
>
> It looks like the AXI stream interface also includes a word array.
> I can't tell though whether this is just a decomposed scatter/gather
> list though.
Hi,
IIRC the word array thing is device specific, not really AXI stream.
I think the whole connection to AXI is a bit unfortunate, these devices
are pretty much the same devices that in other contexts where connected
to other bus standards. Xilinx choose to name them AXI-xxx and I used
the name in our models but I didn't really model anything that is AXI
stream specific..
> There doesn't appear to be a notion of an address though. You could
> make all operations go to address 0 though but it makes me wonder if
> that's stretching the concept of DMA a bit too much.
Yes, IMO we need a different abstraction..
Cheers
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, (continued)
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Anthony Liguori, 2012/06/08
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Peter Crosthwaite, 2012/06/08
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Anthony Liguori, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Peter Maydell, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Edgar E. Iglesias, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Peter Maydell, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Edgar E. Iglesias, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Anthony Liguori, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Peter Maydell, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream,
Edgar E. Iglesias <=
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Peter Crosthwaite, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Edgar E. Iglesias, 2012/06/12
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Peter Crosthwaite, 2012/06/13
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Anthony Liguori, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Avi Kivity, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Anthony Liguori, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI streams, Benjamin Herrenschmidt, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI streams, Anthony Liguori, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI streams, Benjamin Herrenschmidt, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI streams, Anthony Liguori, 2012/06/11