Diff: targets/TARGET_NUVOTON/nu_timer.c

Revision:

188:bcfe06ba3d64

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NUVOTON/nu_timer.c	Thu Nov 08 11:46:34 2018 +0000
@@ -0,0 +1,129 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2015-2016 Nuvoton
+ *
+ * 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 "nu_timer.h"
+#include "mbed_power_mgmt.h"
+#include "mbed_critical.h"
+#include "us_ticker_api.h"
+#include "mbed_assert.h"
+
+void nu_countdown_init(struct nu_countdown_ctx_s *ctx, us_timestamp_t interval_us)
+{
+    core_util_critical_section_enter();
+    sleep_manager_lock_deep_sleep();
+    ctx->_ticker_data = get_us_ticker_data();
+    ctx->_interval_end_us = ticker_read_us(ctx->_ticker_data) + interval_us;
+    ctx->_expired = false;
+    core_util_critical_section_exit();
+}
+
+bool nu_countdown_expired(struct nu_countdown_ctx_s *ctx)
+{
+    core_util_critical_section_enter();
+    if (! ctx->_expired) {
+        ctx->_expired = ticker_read_us(ctx->_ticker_data) >= ctx->_interval_end_us;
+    }
+    core_util_critical_section_exit();
+    
+    return ctx->_expired;
+}
+
+void nu_countdown_free(struct nu_countdown_ctx_s *ctx)
+{
+    core_util_critical_section_enter();
+    sleep_manager_unlock_deep_sleep();
+    core_util_critical_section_exit();
+}
+
+
+void nu_busy_wait_us(uint32_t us)
+{
+    const uint32_t bits = us_ticker_get_info()->bits;
+    const uint32_t mask = (1 << bits) - 1;
+    MBED_ASSERT(us_ticker_get_info()->frequency == 1000000);
+    uint32_t prev = us_ticker_read();
+    while (1) {
+        const uint32_t cur = us_ticker_read();
+        const uint32_t elapsed = (cur - prev) & mask;
+        if (elapsed > us) {
+            break;
+        }
+        us -= elapsed;
+        prev = cur;
+    }
+}
+
+/* Delay 4 cycles per round by hand-counting instruction cycles
+ *
+ * The delay function here is implemented by just hand-counting instruction cycles rather than preferred
+ * H/W timer since it is to use in cases where H/W timer is not available. Usually, it can delay at least
+ * 4-cycles per round.
+ *
+ * In modern pipeline core, plus flash performance and other factors, we cannot rely accurately on hand-
+ * counting instruction cycles for expected delay cycles.
+ */
+#if defined(__CC_ARM)
+MBED_NOINLINE
+__asm void nu_delay_cycle_x4(uint32_t rounds)
+{
+// AStyle should not format inline assembly
+// *INDENT-OFF*
+1
+#if !defined(__CORTEX_M0)
+    NOP                         // 1 cycle
+#endif
+    SUBS a1, a1, #1             // 1 cycle
+    BCS  %BT1                   // 3 cycles(M0)/2 cycles(non-M0)
+    BX   lr
+// *INDENT-ON*
+}
+#elif defined (__ICCARM__)
+MBED_NOINLINE
+void nu_delay_cycle_x4(uint32_t rounds)
+{
+    __asm volatile(
+        "loop: \n"
+#if !defined(__CORTEX_M0)
+        " NOP \n"               // 1 cycle
+#endif
+        " SUBS %0, %0, #1 \n"   // 1 cycle
+        " BCS.n  loop\n"        // 3 cycles(M0)/2 cycles(non-M0)
+        : "+r"(rounds)
+        :
+        : "cc"
+    );
+}
+#elif  defined ( __GNUC__ ) ||  (defined(__ARMCC_VERSION) && (__ARMCC_VERSION >= 6010050))
+MBED_NOINLINE
+void nu_delay_cycle_x4(uint32_t rounds)
+{
+    __asm__ volatile(
+        "%=:\n\t"
+#if !defined(__CORTEX_M0)
+        "NOP\n\t"               // 1 cycle
+#endif
+#if defined(__thumb__) && !defined(__thumb2__) && !defined(__ARMCC_VERSION)
+        "SUB  %0, #1\n\t"       // 1 cycle
+#else
+        "SUBS %0, %0, #1\n\t"   // 1 cycle
+#endif
+        "BCS  %=b\n\t"          // 3 cycles(M0)/2 cycles(non-M0)
+        : "+l"(rounds)
+        :
+        : "cc"
+    );
+}
+#endif