precache() - preload code into the flash cache.

cores/esp8266/core_esp8266_features.cpp

@@ -0,0 +1,50 @@
+
+/*
+ core_esp8266_features.cpp
+
+ Copyright (c) 2019 Mike Nix. All rights reserved.
+ This file is part of the esp8266 core for Arduino environment.
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#include <stdint.h>
+
+/* precache()
+ *  pre-loads flash data into the flash cache
+ *  if f==0, preloads instructions starting at the address we were called from.
+ *  otherwise preloads flash at the given address.
+ *  All preloads are word aligned.
+ */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void precache(void *f, uint32_t bytes) {
+  // Size of a cache page in bytes. We only need to read one word per
+  // page (ie 1 word in 8) for this to work.
+  #define CACHE_PAGE_SIZE 32
+
+  register uint32_t a0 asm("a0");
+  register uint32_t lines = (bytes/CACHE_PAGE_SIZE)+2;
+  volatile uint32_t *p = (uint32_t*)((f ? (uint32_t)f : a0) & ~0x03);
+  uint32_t x;
+  for (uint32_t i=0; i<lines; i++, p+=CACHE_PAGE_SIZE/sizeof(uint32_t)) x=*p;
+  (void)x;
+}
+
+#ifdef __cplusplus
+}
+#endif

cores/esp8266/core_esp8266_features.h

@@ -93,4 +93,26 @@ inline uint32_t esp_get_cycle_count() {
 }
 #endif // not CORE_MOCK
 
+
+// Tools for preloading code into the flash cache
+#define PRECACHE_ATTR __attribute__((optimize("no-reorder-blocks"))) \
+                      __attribute__((noinline))
+
+#define PRECACHE_START(tag) \
+    precache(NULL,(uint8_t *)&&_precache_end_##tag - (uint8_t*)&&_precache_start_##tag); \
+    _precache_start_##tag:
+
+#define PRECACHE_END(tag) \
+    _precache_end_##tag:
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void precache(void *f, uint32_t bytes);
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif // CORE_ESP8266_FEATURES_H