K64F/K22F: Implement HAL lp_timer API

API implemented using hybrid approach with RTC for longer periods and
LPTMR for subsecond ones.

Author: bulislaw

hal/targets.json

@@ -524,7 +524,7 @@
         "inherits": ["Target"],
         "progen": {"target": "frdm-k22f"},
         "detect_code": ["0231"],
-        "device_has": ["ANALOGIN", "ANALOGOUT", "ERROR_RED", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES"],
+        "device_has": ["ANALOGIN", "ANALOGOUT", "ERROR_RED", "I2C", "I2CSLAVE", "INTERRUPTIN", "LOWPOWERTIMER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES"],
         "release_versions": ["2", "5"]
     },
     "KL27Z": {
@@ -565,7 +565,7 @@
         "inherits": ["Target"],
         "progen": {"target": "frdm-k64f"},
         "detect_code": ["0240"],
-        "device_has": ["ANALOGIN", "ANALOGOUT", "ERROR_RED", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_FC", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES", "STORAGE"],
+        "device_has": ["ANALOGIN", "ANALOGOUT", "ERROR_RED", "I2C", "I2CSLAVE", "INTERRUPTIN", "LOWPOWERTIMER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_FC", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES", "STORAGE"],
         "features": ["IPV4", "STORAGE"],
         "release_versions": ["2", "5"]
     },

hal/targets/hal/TARGET_Freescale/TARGET_KSDK2_MCUS/api/lp_ticker.c

@@ -0,0 +1,172 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2016 ARM Limited
+ *
+ * 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.
+ */
+
+#if DEVICE_LOWPOWERTIMER
+
+#include "lp_ticker_api.h"
+#include "fsl_rtc.h"
+#include "fsl_lptmr.h"
+#include "cmsis.h"
+#include "rtc_api.h"
+
+#define MAX_SEC_BITS (12)
+#define MAX_SEC_MASK ((1 << MAX_SEC_BITS) - 1)
+#define SEC_IN_USEC (1000000)
+#define OSC32K_CLK_HZ (32768)
+#define MAX_LPTMR_SLEEP ((1 << 16) - 1)
+
+static bool lp_ticker_inited = false;
+static int lptmr_schedule = 0;
+
+static void rtc_isr(void)
+{
+    RTC_DisableInterrupts(RTC, kRTC_AlarmInterruptEnable);
+    RTC->TAR = 0; /* Write clears the IRQ flag */
+
+    /* Wait subsecond remainder if any */
+    if (lptmr_schedule) {
+        LPTMR_SetTimerPeriod(LPTMR0, lptmr_schedule);
+        LPTMR_EnableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
+        LPTMR_StartTimer(LPTMR0);
+    } else {
+        lp_ticker_irq_handler();
+    }
+}
+
+static void lptmr_isr(void)
+{
+    LPTMR_ClearStatusFlags(LPTMR0, kLPTMR_TimerCompareFlag);
+    LPTMR_StopTimer(LPTMR0);
+
+    lp_ticker_irq_handler();
+}
+
+/** Initialize the low power ticker
+ *
+ */
+void lp_ticker_init(void)
+{
+    lptmr_config_t lptmrConfig;
+
+    if (lp_ticker_inited) {
+        return;
+    }
+    lp_ticker_inited = true;
+
+    /* Setup low resolution clock - RTC */
+    if (!rtc_isenabled()) {
+        rtc_init();
+        RTC_DisableInterrupts(RTC, kRTC_AlarmInterruptEnable | kRTC_SecondsInterruptEnable);
+        RTC_StartTimer(RTC);
+    }
+
+    NVIC_ClearPendingIRQ(RTC_IRQn);
+    NVIC_SetVector(RTC_IRQn, (uint32_t)rtc_isr);
+    NVIC_EnableIRQ(RTC_IRQn);
+
+    /* Setup high resolution clock - LPTMR */
+    LPTMR_GetDefaultConfig(&lptmrConfig);
+    /* Use 32kHz drive */
+    CLOCK_SetXtal32Freq(OSC32K_CLK_HZ);
+    lptmrConfig.prescalerClockSource = kLPTMR_PrescalerClock_2;
+    LPTMR_Init(LPTMR0, &lptmrConfig);
+    LPTMR_EnableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
+    NVIC_ClearPendingIRQ(LPTMR0_IRQn);
+    NVIC_SetVector(LPTMR0_IRQn, (uint32_t)lptmr_isr);
+    EnableIRQ(LPTMR0_IRQn);
+}
+
+/** Read the current counter
+ *
+ * @return The current timer's counter value in microseconds
+ */
+uint32_t lp_ticker_read(void)
+{
+    uint32_t sec, pre;
+
+    if (!lp_ticker_inited) {
+        lp_ticker_init();
+    }
+
+    sec = RTC->TSR; /* 32b: Seconds */
+    pre = RTC->TPR; /* 16b: Increments every 32.768kHz clock cycle (30us) */
+
+    /* Final value: 11b (4095) for sec and 21b for usec (pre can reach 1,000,000us which is close to 1<<20) */
+    uint32_t ret = (((sec & MAX_SEC_MASK) * SEC_IN_USEC) + (((uint64_t)pre * SEC_IN_USEC) / OSC32K_CLK_HZ));
+
+    return ret;
+}
+
+/** Set interrupt for specified timestamp
+ *
+ * @param timestamp The time in microseconds to be set
+ */
+void lp_ticker_set_interrupt(timestamp_t timestamp)
+{
+    uint32_t now_us, delta_us, delta_ticks;
+
+    if (!lp_ticker_inited) {
+        lp_ticker_init();
+    }
+
+    lptmr_schedule = 0;
+    now_us = lp_ticker_read();
+    delta_us = timestamp > now_us ? timestamp - now_us : (uint32_t)((uint64_t)timestamp + 0xFFFFFFFF - now_us);
+
+    /* Checking if LPTRM can handle this sleep */
+    delta_ticks = USEC_TO_COUNT(delta_us, CLOCK_GetFreq(kCLOCK_Er32kClk));
+    if (delta_ticks > MAX_LPTMR_SLEEP) {
+        /* Using RTC if wait time is over 16b (2s @32kHz) */
+        uint32_t delta_sec;
+
+        delta_us += COUNT_TO_USEC(RTC->TPR, CLOCK_GetFreq(kCLOCK_Er32kClk)); /* Accounting for started second */
+        delta_sec = delta_us / SEC_IN_USEC;
+        delta_us -= delta_sec * SEC_IN_USEC;
+
+        RTC->TAR = RTC->TSR + delta_sec - 1;
+
+        RTC_EnableInterrupts(RTC, kRTC_AlarmInterruptEnable);
+
+        /* Set aditional, subsecond, sleep time */
+        if (delta_us) {
+            lptmr_schedule = USEC_TO_COUNT(delta_us, CLOCK_GetFreq(kCLOCK_Er32kClk));
+        }
+    } else {
+        /* Below RTC resolution using LPTMR */
+        LPTMR_SetTimerPeriod(LPTMR0, delta_ticks);
+        LPTMR_EnableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
+        LPTMR_StartTimer(LPTMR0);
+    }
+}
+
+/** Disable low power ticker interrupt
+ *
+ */
+void lp_ticker_disable_interrupt(void)
+{
+    LPTMR_DisableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
+    RTC_DisableInterrupts(RTC, kRTC_AlarmInterruptEnable);
+}
+
+/** Clear the low power ticker interrupt
+ *
+ */
+void lp_ticker_clear_interrupt(void)
+{
+    RTC->TAR = 0; /* Write clears the IRQ flag */
+    LPTMR_ClearStatusFlags(LPTMR0, kLPTMR_TimerCompareFlag);
+}
+#endif /* DEVICE_LOWPOWERTIMER */