SoC+fpga, over AXI, AMBA bus

[ataradov]

the devicetree just tells what drivers to load and how to configure them

Yep, and this "driver" is just an old way of doing the same. It is only used by a few unsupported boards to specify hardcoded hardware configuration.

[langwadt]

something simple like loading a different configuration for the programmable logic will require that you kill all programs and unload all drivers that might access the axi bus to that logic

Otherwise you will have to write all your software to be able to deal with timeouts. From a programmer point of view, they will have to look like some value (0?) is returned for reads and writes that go nowhere. That is unless you want to handle exceptions.

I'd much rated handle a crashed program/driver or exceptions, than a system that hang until someone hits the reset button

All of this is a hell for a programmer. It is much easier to stop accessing locations before they disappear.

I disagree

Also, ARM implementation of AXI allows you to connect a default slave that handles all unhanded request. Just use that if your implementation allows it.

it won't help the problem is not unhanded request it is transactions that never finish

[ataradov]

it won't help the problem is not unhanded request it is transactions that never finish

What do you mean? If your software makes a request that is not handled by any of thew real slaves, this default slave takes over and completes the transaction.

Of your are saying that your slave disappears right in the middle of the transaction? I don't  think this bus is designed to handle this level of dynamic reconfiguration. I don't think any existing bus can do this. That's just stupid to expect that slave can disappear in the middle of the transaction.

[langwadt]

it won't help the problem is not unhanded request it is transactions that never finish

What do you mean? If your software makes a request that is not handled by any of thew real slaves, this default slave takes over and completes the transaction.

Of your are saying that your slave disappears right in the middle of the transaction? I don't  think this bus is designed to handle this level of dynamic reconfiguration. I don't think any existing bus can do this. That's just stupid to expect that slave can disappear in the middle of the transaction.

if the slave disappears during a transaction or isn't there when a transaction is started the system
end up in a a dead lock. Once a master has set xVALID it must wait for xREADY

dynamic reconfiguration is entirely reasonable in a system with configurable logic.
A bus that crashes the whole system waiting forever on something that ought to take microseconds
is silly

[ataradov]

dynamic reconfiguration is entirely reasonable in a system with configurable logic.

You do whatever you want of course, but don't blame the bus that it does no handle devices disappearing in the middle of transaction. That's just bad system design and there is no need to over complicate the bus logic for things that will never happen in actual real life.

[langwadt]

dynamic reconfiguration is entirely reasonable in a system with configurable logic.

You do whatever you want of course, but don't blame the bus that it does no handle devices disappearing in the middle of transaction. That's just bad system design and there is no need to over complicate the bus logic for things that will never happen in actual real life.

that's like saying why bother with protected memory or exceptions it is never going to happen in
real life and if it does it is just bad system design

[legacy]

not brilliant, but it's extremely good, this link shows a bit of the magic under the hood: Exploring the Arrow SoCKit Part III - Controlling FPGA from Software   

[legacy]

Design and Implementation of AMBA-AHB&APB bridge memory controller by VHDL

[legacy]

what is the equivalent of De1 in the Xilinx world ? (SoC/ARM + FPGA, with a bus-bridge in the middle)

[ataradov]

Any board based on Zynq. Prices vary a lot, so pick whatever fits your bill.

[legacy]

yes, I meant within the same price as De1, and … is it this one ?

[ataradov]

http://zedboard.org/ is one of the most famous. There are many variations with wide rage of prices. Community support is there.

The cheapest one is actually a board from Adapteva, but their site seems to be down at the moment.

[Kilrah]

I've got a Zybo, and waiting for my snickerdoodle.
https://www.crowdsupply.com/krtkl/snickerdoodle

Still in preproduction, but it'll be a very cheap entry price.

[legacy]

https://www.crowdsupply.com/krtkl/snickerdoodle]snickerdoodle seems good