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/*
* SPDX-FileCopyrightText: Copyright 2022 Arm Limited and/or its affiliates <open-source-office@arm.com>
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "ethosu_cpu_cache.h"
#include "RTE_Components.h" /* For CPU related defintiions */
#include "ethosu_driver.h" /* Arm Ethos-U driver header */
#include "log_macros.h" /* Logging macros */
/** Structure to maintain data cache states. */
typedef struct _cpu_cache_state {
uint32_t dcache_invalidated : 1;
uint32_t dcache_cleaned : 1;
} cpu_cache_state;
/** Static CPU cache state object.
* @note This logic around flipping these states is based on the driver
* calling the functions in this sequence:
*
* Cache flush (ethosu_flush_dcache)
* ↓
* Start inference (ethosu_inference_begin)
* ↓
* Inference (ethosu_dev_run_command_stream)
* ↓
* End inference (ethosu_inference_end)
* ↓
* Cache invalidate (ethosu_dcache_invalidate)
**/
static cpu_cache_state s_cache_state = {.dcache_cleaned = 0, .dcache_invalidated = 0};
/**
* @brief Gets the current CPU cache state.
* @return Pointer to the CPU cache state object.
*/
static cpu_cache_state* ethosu_get_cpu_cache_state(void)
{
return &s_cache_state;
}
void ethosu_clear_cache_states(void)
{
cpu_cache_state* const state = ethosu_get_cpu_cache_state();
trace("Clearing cache state members\n");
state->dcache_invalidated = 0;
state->dcache_cleaned = 0;
}
void ethosu_flush_dcache(uint32_t *p, size_t bytes)
{
UNUSED(p);
UNUSED(bytes);
#if defined (__DCACHE_PRESENT) && (__DCACHE_PRESENT == 1U)
cpu_cache_state* const state = ethosu_get_cpu_cache_state();
if (SCB->CCR & SCB_CCR_DC_Msk) {
/**
* @note We could choose to call the `SCB_CleanDCache_by_Addr` function
* here, but the sizes which this function is called for, can
* cause unnecessary delays. It's worth noting that this function
* is called from the Arm Ethos-U NPU drive repeatedly for each
* region it accesses. This could even be RO memory which does
* not need cache maintenance, along with parts of the input and
* output tensors which rightly need to be cleaned. Therefore, to
* reduce overhead of repeated calls for large memory sizes, we
* call the clean and invalidation functions for whole cache.
*
* If the neural network to be executed is completely falling
* onto the NPU, consider disabling the data cache altogether
* for the duration of the inference to further reduce the cache
* maintenance burden in these functions.
*/
/** Clean the cache if it hasn't been cleaned already */
if (!state->dcache_cleaned) {
trace("Cleaning data cache\n");
SCB_CleanDCache();
/** Assert the cache cleaned state and clear the invalidation
* state. */
state->dcache_cleaned = 1;
state->dcache_invalidated = 0;
}
}
#endif /* defined (__DCACHE_PRESENT) && (__DCACHE_PRESENT == 1U) */
}
void ethosu_invalidate_dcache(uint32_t *p, size_t bytes)
{
UNUSED(p);
UNUSED(bytes);
#if defined (__DCACHE_PRESENT) && (__DCACHE_PRESENT == 1U)
cpu_cache_state* const state = ethosu_get_cpu_cache_state();
if (SCB->CCR & SCB_CCR_DC_Msk) {
/**
* See note in ethosu_flush_dcache function for why we clean the whole
* cache instead of calling it for specific addresses.
**/
if (!state->dcache_invalidated) {
trace("Invalidating data cache\n");
SCB_InvalidateDCache();
/** Assert the cache invalidation state and clear the clean
* state. */
state->dcache_invalidated = 1;
state->dcache_cleaned = 0;
}
}
#endif /* defined (__DCACHE_PRESENT) && (__DCACHE_PRESENT == 1U) */
}
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