Running two RTEMS instances on two RISC-V harts

Mon Oct 24 12:13:02 UTC 2022

Hi Jens,

Is there a real need to have the telescope driver twice in memory?
Would it be enough to implement the driver as “object oriented” in C?
Then you would just need to create a context struct during initialization based on the hartid with the correct interrupt assignment and base address of the memory mapped registers.

At least that is a common pattern in the driver implementations of RTEMS.

Best regards,

    Jan

PS: It is probably a good idea to remove the disclaimer in your email footer before posting to a public mailinglist.

From: users <users-bounces at rtems.org> On Behalf Of Schweikhardt, Jens (TSPCE6-TL5)
Sent: Montag, 24. Oktober 2022 13:53
To: 'users at rtems.org' <users at rtems.org>
Subject: Running two RTEMS instances on two RISC-V harts

hello, world\n

we’re currently in the design phase for a rocketchip RISC-V project with two harts.
Think a common HW platform where each hart drives a separate telescope unit.
The C code for each telescope is basically identical with the exception of memory mapped registers and interrupts.
Our idea is to compile the C code twice and link with different linkerscripts, separating the images in RAM
via different MEMORY { RAM: ORIGIN = 0x######## } declarations. A bootloader loads the images
to different addresses and branches depending on mhartid, starting two separate RTEMS applications, each
of which runs 10 tasks. There’s no communication between the RTEMS instances.

Are we attempting something crazy (too complex) and we should instead look into <your suggestion here>?

If not, is there a simple way to compile an app twice for different RAM: ORIGIN values?
I tried using a Linkerscript with -Wl,-T,Linkerscript with a different MEMORY but this draws a warning such as
warning: redeclaration of memory region `RAM'
and uses the value in the BSPs  linkcmds file. It looks like the last declaration wins and the linkcmds is
always read after linker scripts specified by my -Wl command line option.

Jens Schweikhardt

TL4 LCT Software Development

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