esp8266/xtirq: Add xtirq.h for controlling xtensa irqs.

esp8266/xtirq.h

+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef __MICROPY_INCLUDED_ESP8266_XTIRQ_H__
+#define __MICROPY_INCLUDED_ESP8266_XTIRQ_H__
+
+#include <stdint.h>
+
+// returns the value of "intlevel" from the PS register
+static inline uint32_t query_irq(void) {
+    uint32_t ps;
+    __asm__ volatile("rsr %0, ps" : "=a" (ps));
+    return ps & 0xf;
+}
+
+// irqs with a priority value lower or equal to "intlevel" will be disabled
+// "intlevel" should be between 0 and 15 inclusive, and should be an integer
+static inline uint32_t raise_irq_pri(uint32_t intlevel) {
+    uint32_t old_ps;
+    __asm__ volatile ("rsil %0, %1" : "=a" (old_ps) : "I" (intlevel));
+    return old_ps;
+}
+
+// "ps" should be the value returned from raise_irq_pri
+static inline void restore_irq_pri(uint32_t ps) {
+    __asm__ volatile ("wsr %0, ps; rsync" :: "a" (ps));
+}
+
+static inline uint32_t disable_irq(void) {
+    return raise_irq_pri(15);
+}
+
+static inline void enable_irq(uint32_t irq_state) {
+    restore_irq_pri(irq_state);
+}
+
+#endif // __MICROPY_INCLUDED_ESP8266_XTIRQ_H__