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39 lines
1.3 KiB
C
39 lines
1.3 KiB
C
/*
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* Copyright 2024 Google LLC
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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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#include "mcu/fpu.h"
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#define CMSIS_COMPATIBLE
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#include <mcu.h>
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#include <stdint.h>
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void mcu_fpu_cleanup(void) {
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// The lazy stacking mechanism for the Cortex M4 starts stacking FPU
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// registers during context switches once the thread has used the FPU
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// once. This is problematic because this bumps the stack cost of a context
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// switch by an additional 132 bytes. This routine resets the FPCA bit which
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// controls whether or not this stacking takes place
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// For the Cortex M3, this routine is a no-op
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const uint32_t fpca_bit_mask = 0x4;
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uint32_t control = __get_CONTROL();
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if ((control & fpca_bit_mask) != 0) {
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control &= ~fpca_bit_mask;
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__set_CONTROL(control);
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}
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}
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