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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choice
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prompt "RISCV32 configuration selection"
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depends on RISCV32
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source "arch/riscv32/soc/*/Kconfig.soc"
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endchoice
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menu "RISCV32 Options"
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depends on RISCV32
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config ARCH
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string
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default "riscv32"
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config ARCH_DEFCONFIG
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string
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default "arch/riscv32/defconfig"
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menu "RISCV32 Processor Options"
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config INCLUDE_RESET_VECTOR
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bool "Include Reset vector"
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default n
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help
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Include the reset vector stub that inits CPU and then jumps to __start
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config IRQ_OFFLOAD
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bool "Enable IRQ offload"
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default n
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help
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Enable irq_offload() API which allows functions to be synchronously
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run in interrupt context. Mainly useful for test cases.
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config RISCV_SOC_CONTEXT_SAVE
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bool "Enable SOC-based context saving in IRQ handler"
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default n
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help
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Enable SOC-based context saving, for SOCS which require saving of
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extra registers when entering an interrupt/exception
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config RISCV_SOC_INTERRUPT_INIT
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bool "Enable SOC-based interrupt initialization"
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default n
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help
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Enable SOC-based interrupt initialization
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(call soc_interrupt_init, within _IntLibInit when enabled)
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config RISCV_GENERIC_TOOLCHAIN
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bool "Compile using generic riscv32 toolchain"
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default y
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help
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Compile using generic riscv32 toolchain.
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Allow SOCs that have custom extended riscv ISA to still
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compile with generic riscv32 toolchain.
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config RISCV_HAS_CPU_IDLE
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bool "Does SOC has CPU IDLE instruction"
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default n
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help
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Does SOC has CPU IDLE instruction
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endmenu
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source "arch/riscv32/soc/*/Kconfig"
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endmenu
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