added the riscv-privilege SOC_FAMILY, under which all
riscv SOCs supporting the riscv privilege architecture
specifcation shall reside. These SOCs shall notably have
a common base for handling IRQs.
Moved riscv32-qemu under the riscv-privilege SOC_FAMILY
Change-Id: I5372cb38e3eaed78886f22b212ab4f881ef30b3f
Signed-off-by: Jean-Paul Etienne <fractalclone@gmail.com>
Added a riscv-privilege.h header file that contains common
definitions for all riscv SOCs supporting the riscv
privileged architecture specification.
This shall ease addition of future riscv SOCs supporting
the riscv privileged architecture spec.
Change-Id: I5714bf70eeda738a25967ed26d3d0d2aaa0c9989
Signed-off-by: Jean-Paul Etienne <fractalclone@gmail.com>
Added a linker script that shall be common to most riscv SOCs.
Linker script also accounts for execution in place in ROM, when
CONFIG_XIP is set.
Nonetheless, riscv32 SOCs (like pulpino) requiring a different
system layout can still define their own linker script.
Change-Id: I3ad670446d439772c29a8204e307ac79643dc650
Signed-off-by: Jean-Paul Etienne <fractalclone@gmail.com>
RISC-V is an open-source instruction set architecture.
Added support for the 32bit version of RISC-V to Zephyr.
1) exceptions/interrupts/faults are handled at the architecture
level via the __irq_wrapper handler. Context saving/restoring
of registers can be handled at both architecture and SOC levels.
If SOC-specific registers need to be saved, SOC level needs to
provide __soc_save_context and __soc_restore_context functions
that shall be accounted by the architecture level, when
corresponding config variable RISCV_SOC_CONTEXT_SAVE is set.
2) As RISC-V architecture does not provide a clear ISA specification
about interrupt handling, each RISC-V SOC handles it in its own
way. Hence, at the architecture level, the __irq_wrapper handler
expects the following functions to be provided by the SOC level:
__soc_is_irq: to check if the exception is the result of an
interrupt or not.
__soc_handle_irq: handle pending IRQ at SOC level (ex: clear
pending IRQ in SOC-specific IRQ register)
3) Thread/task scheduling, as well as IRQ offloading are handled via
the RISC-V system call ("ecall"), which is also handled via the
__irq_wrapper handler. The _Swap asm function just calls "ecall"
to generate an exception.
4) As there is no conventional way of handling CPU power save in
RISC-V, the default nano_cpu_idle and nano_cpu_atomic_idle
functions just unlock interrupts and return to the caller, without
issuing any CPU power saving instruction. Nonetheless, to allow
SOC-level to implement proper CPU power save, nano_cpu_idle and
nano_cpu_atomic_idle functions are defined as __weak
at the architecture level.
Change-Id: I980a161d0009f3f404ad22b226a6229fbb492389
Signed-off-by: Jean-Paul Etienne <fractalclone@gmail.com>
Jean-Paul Etienne