/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include <stdlib.h> #include "pico/stdlib.h" #include "hardware/structs/xip_ctrl.h" // Example of using cache hit/access counters, and showing the effect of // invalidate on cache miss/hit. const uint32_t test_data[8] = {0, 1, 2, 3, 4, 5, 6, 7}; void __no_inline_not_in_flash_func(check)(bool cond, const char *msg) { if (!cond) { puts(msg); exit(-1); } } void __no_inline_not_in_flash_func(check_hit_miss_invalidate)() { io_rw_32 *test_data_ptr = (io_rw_32 *) test_data; /// \tag::check_hit_miss_invalidate[] // Flush cache to make sure we miss the first time we access test_data xip_ctrl_hw->flush = 1; while (!(xip_ctrl_hw->stat & XIP_STAT_FLUSH_READY_BITS)) tight_loop_contents(); // Clear counters (write any value to clear) xip_ctrl_hw->ctr_acc = 1; xip_ctrl_hw->ctr_hit = 1; (void) *test_data_ptr; check(xip_ctrl_hw->ctr_hit == 0 && xip_ctrl_hw->ctr_acc == 1, "First access to data should miss"); (void) *test_data_ptr; check(xip_ctrl_hw->ctr_hit == 1 && xip_ctrl_hw->ctr_acc == 2, "Second access to data should hit"); // Write to invalidate individual cache lines (64 bits) // Writes must be directed to the cacheable, allocatable alias (address 0x10.._....) *test_data_ptr = 0; (void) *test_data_ptr; check(xip_ctrl_hw->ctr_hit == 1 && xip_ctrl_hw->ctr_acc == 3, "Should miss after invalidation"); (void) *test_data_ptr; check(xip_ctrl_hw->ctr_hit == 2 && xip_ctrl_hw->ctr_acc == 4, "Second access after invalidation should hit again"); /// \end::check_hit_miss_invalidate[] } // Some code which achieves a very high cache hit rate: int recursive_fibonacci(int n) { if (n <= 1) return 1; else return recursive_fibonacci(n - 1) + recursive_fibonacci(n - 2); } int main() { stdio_init_all(); uint hit = xip_ctrl_hw->ctr_hit; uint access = xip_ctrl_hw->ctr_acc; if (access == 0) printf("It looks like you're running this example from SRAM. This probably won't go well!\n"); // Note the hit rate will appear quite low at boot, as the .data, // .time_critical init in crt0 read a lot of read-once data from flash printf("At boot: %d hits, %d accesses\n", hit, access); printf("Hit rate so far: %.1f%%\n", hit * 100.f / access); printf("Calculate 25th fibonacci number: %d\n", recursive_fibonacci(25)); uint32_t ctr_hit = xip_ctrl_hw->ctr_hit; uint32_t ctr_acc = xip_ctrl_hw->ctr_acc; printf("New hit rate after printf and fibonacci: %.1f%%\n", ctr_hit * 100.f / ctr_acc); check_hit_miss_invalidate(); printf("Hit/miss check passed\n"); return 0; }

This firmware image was imported from the pico-examples repository. 


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