arch: added support for the riscv32 architecture
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>
2017-01-11 07:24:30 +08:00
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/*
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* Copyright (c) 2016 Jean-Paul Etienne <fractalclone@gmail.com>
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*
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2017-01-19 09:01:01 +08:00
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* SPDX-License-Identifier: Apache-2.0
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arch: added support for the riscv32 architecture
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>
2017-01-11 07:24:30 +08:00
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*/
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/**
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* @file
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* @brief Full C support initialization
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*
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*
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* Initialization of full C support: zero the .bss and call _Cstart().
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*
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* Stack is available in this module, but not the global data/bss until their
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* initialization is performed.
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*/
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#include <stddef.h>
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#include <toolchain.h>
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#include <nano_internal.h>
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/**
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*
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* @brief Prepare to and run C code
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*
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* This routine prepares for the execution of and runs C code.
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*
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* @return N/A
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*/
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void _PrepC(void)
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{
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_bss_zero();
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2017-02-01 09:25:26 +08:00
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#ifdef CONFIG_XIP
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_data_copy();
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#endif
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arch: added support for the riscv32 architecture
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>
2017-01-11 07:24:30 +08:00
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_Cstart();
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CODE_UNREACHABLE;
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}
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