EPeak Daily

Inter Processor Communication (Half 1)

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Lots of our options include a number of processors, both hardcore processors such because the Arm A9, A53 or R5, softcores likes MicroBlaze, Arm Cortex-M1/M3, or a mixture of the 2.

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Once we implement a multi-processor resolution, sometimes we cut up the tasking between the obtainable cores, exploiting every core to maximise its efficiency attributes. For instance, utilizing MicroBlaze or Cortex cores within the PL for devoted real-time offloaded duties whereas utilizing hardcore utility processors for increased degree features.

After all, to appropriately implement a multi-processor resolution utility, all of the processors within the resolution want to have the ability to talk and share the obtainable system assets safely and reliably.

That is the place inter processor communication (IPC) is available in; when appropriately carried out, it allows secure and dependable communication between processors, whereas additionally permitting a number of processors to share widespread assets, e.g. UARTs with out battle inflicting corruption.

In earlier MicroZed Chronicles, now we have explored each the OpenAMP framework and Zynq MPSoC Inter Processor Interrupts. Nevertheless, now we have by no means examined IPC options carried out utilizing Mailboxes and MUTEXs.

Each Mailboxes and MUTEX play differing roles in our IPC resolution:

  • Mailbox — Permits bi-directional communication between a number of processors utilizing a FIFO primarily based strategy to messaging.
  • MUTEX — Implement mutual exclusion locks, this permits processors to lock shared assets stopping a number of accesses on the identical time.

No matter if we use a heterogeneous SoC or FPGA, each Mailboxes and MUTEX’s are carried out inside the programmable logic (PL).

We will implement Mailboxes and MUTEXs in our design straight from the Xilinx IP library. As each are meant for communication between two processors, they’ve two slave AXI inputs.

One slave AXI interface for every processor, utilizing the Mailbox or MUTEX.

On this instance, we going to make use of a Zynq speaking and sharing assets with a MicroBlaze within the PL.

The MicroBlaze might be related to the GPIO which drives LEDs. My plan for the software program utility within the subsequent weblog is to indicate how we will ship messages from the A9 to the MicroBlaze to activate and off LEDs. A easy however efficient demonstration, though first we have to full the {hardware} design.

To create the block diagram, we first want so as to add in a Zynq processing system IP and run the block automation to configure the Zynq for the chosen board.

That’s one processing system added. For the second, add a MicroBlaze utilizing the IP catalog. As soon as the MicroBlaze IP is within the block diagram, double click on to re-customize the IP, choose the microcontroller preset, leaving all different choices unchanged.

As soon as the MicroBlaze IP is configured, the subsequent step is to run its block automation to create the MicroBlaze resolution. It will add within the block RAM from which the MicroBlaze will run and debug amenities.

Now which have our two processing system options, we’re prepared so as to add within the Mailbox and MUTEX — each might be added from Xilinx IP Catalog.

As soon as performed, we will use the connection automation wizard to attach them into the 2 processor methods AXI connections.

Connection automation settings for the Zynq PS connection
Connection automation settings for the MicroBlaze

The Mailbox transfers messages utilizing a FIFO, the depth of this may be configured by re-using the Mailbox IP. To make sure environment friendly processing of messages on the receiving processor, the Mailbox is able to producing interrupts to the related processor when messages are queued.

Just like the Mailbox, the MUTEX could be very related, besides it doesn’t use a FIFO as a substitute registers are used for every MUTEX to point the locked standing or not. We will have as much as 32 MUTEX shared between as much as eight processors.

We are going to look at it extra within the SW implementation weblog subsequent week however to forestall processors unlocking MUTEXs inadvertently or maliciously, CPU IDs are used.

The finished block diagram ought to look much like the one under.

We will now construct the {hardware} and export the design to SDK, prepared to write down the SW utility subsequent week.

Till then!

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