cd83e85edc
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>
119 lines
2.9 KiB
C
119 lines
2.9 KiB
C
/*
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* Copyright (c) 2010-2014 Wind River Systems, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* @file
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* @brief Common toolchain abstraction
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*
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* Macros to abstract compiler capabilities (common to all toolchains).
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*/
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/* Abstract use of extern keyword for compatibility between C and C++ */
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#ifdef __cplusplus
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#define EXTERN_C extern "C"
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#else
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#define EXTERN_C extern
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#endif
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/* Use TASK_ENTRY_CPP to tag task entry points defined in C++ files. */
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#ifdef __cplusplus
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#define TASK_ENTRY_CPP extern "C"
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#endif
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/*
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* Generate a reference to an external symbol.
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* The reference indicates to the linker that the symbol is required
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* by the module containing the reference and should be included
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* in the image if the module is in the image.
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*
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* The assembler directive ".set" is used to define a local symbol.
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* No memory is allocated, and the local symbol does not appear in
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* the symbol table.
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*/
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#ifdef _ASMLANGUAGE
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#define REQUIRES(sym) .set sym ## _Requires, sym
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#else
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#define REQUIRES(sym) __asm__ (".set " # sym "_Requires, " # sym "\n\t");
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#endif
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#ifdef _ASMLANGUAGE
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#define SECTION .section
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#endif
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/*
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* If the project is being built for speed (i.e. not for minimum size) then
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* align functions and branches in executable sections to improve performance.
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*/
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#ifdef _ASMLANGUAGE
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#ifdef CONFIG_X86
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#ifdef PERF_OPT
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#define PERFOPT_ALIGN .balign 16
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#else
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#define PERFOPT_ALIGN .balign 1
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#endif
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#elif defined(CONFIG_ARM)
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#ifdef CONFIG_ISA_THUMB
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#define PERFOPT_ALIGN .balign 2
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#else
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#define PERFOPT_ALIGN .balign 4
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#endif
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#elif defined(CONFIG_ARC)
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#define PERFOPT_ALIGN .balign 4
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#elif defined(CONFIG_NIOS2) || defined(CONFIG_RISCV32)
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#define PERFOPT_ALIGN .balign 4
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#else
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#error Architecture unsupported
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#endif
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#define GC_SECTION(sym) SECTION .text.##sym, "ax"
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#endif /* _ASMLANGUAGE */
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/* force inlining a function */
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#if !defined(_ASMLANGUAGE)
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#define ALWAYS_INLINE inline __attribute__((always_inline))
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#endif
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#define _STRINGIFY(x) #x
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#define STRINGIFY(s) _STRINGIFY(s)
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/* Indicate that an array will be used for stack space. */
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#define __stack __aligned(STACK_ALIGN)
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/* concatenate the values of the arguments into one */
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#define _DO_CONCAT(x, y) x ## y
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#define _CONCAT(x, y) _DO_CONCAT(x, y)
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/* compile-time assertion that makes the build fail */
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#define BUILD_ASSERT(EXPR) typedef char __build_assert_failure[(EXPR) ? 1 : -1]
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