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0120ddaf7f
The barriers (as recommended per the STM32 programming manual) ensure that the FPU is correctly enabled before continuing and potentially executing any FPU instructions, however rare that may be during startup. Change-Id: I846c87c5fd72ac297ed6556e57cb7ca672d6d83a Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/13360 Commit-Queue: Ian Tessier <itessier@google.com> Commit-Queue: Keir Mierle <keir@google.com> Reviewed-by: Keir Mierle <keir@google.com>
68 lines
2.3 KiB
C++
68 lines
2.3 KiB
C++
// Copyright 2020 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://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, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#include "pw_boot_armv7m/boot.h"
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#include "pw_malloc/malloc.h"
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#include "pw_preprocessor/compiler.h"
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#include "pw_sys_io_baremetal_stm32f429/init.h"
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// Note that constexpr is used inside of this function instead of using a static
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// constexpr or declaring it outside of this function in an anonymous namespace,
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// because constexpr makes it available for the compiler to evaluate during
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// copmile time but does NOT require it to be evaluated at compile team and we
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// have to be incredibly careful that this does not end up in the .data section.
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void pw_boot_PreStaticMemoryInit() {
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// TODO(pwbug/17): Optionally enable Replace when Pigweed config system is
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// added.
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#if PW_ARMV7M_ENABLE_FPU
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// Enable FPU if built using hardware FPU instructions.
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// CPCAR mask that enables FPU. (ARMv7-M Section B3.2.20)
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constexpr uint32_t kFpuEnableMask = (0xFu << 20);
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// Memory mapped register to enable FPU. (ARMv7-M Section B3.2.2, Table B3-4)
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volatile uint32_t& arm_v7m_cpacr =
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*reinterpret_cast<volatile uint32_t*>(0xE000ED88u);
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arm_v7m_cpacr |= kFpuEnableMask;
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// Ensure the FPU configuration is committed and enabled before continuing and
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// potentially executing any FPU instructions, however rare that may be during
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// startup.
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asm volatile(
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" dsb \n"
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" isb \n"
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// clang-format off
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: /*output=*/
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: /*input=*/
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: /*clobbers=*/"memory"
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// clang-format on
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);
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#endif // PW_ARMV7M_ENABLE_FPU
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}
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void pw_boot_PreStaticConstructorInit() {
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#if PW_MALLOC_ACTIVE
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pw_MallocInit();
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#endif // PW_MALLOC_ACTIVE
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}
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void pw_boot_PreMainInit() { pw_sys_io_Init(); }
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PW_NO_RETURN void pw_boot_PostMain() {
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// In case main() returns, just sit here until the device is reset.
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while (true) {
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}
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PW_UNREACHABLE;
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}
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