Merge pull request #8737 from kapi90/cm3ds_lp_requirements

Add low power implementations for CM3DS

Author: 0xc0170

targets/TARGET_ARM_SSG/TARGET_CM3DS_MPS2/device/device_cfg.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018 ARM Limited
+ * Copyright (c) 2018 Arm Limited
  *
  * Licensed under the Apache License Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,8 +27,54 @@
  */
 
 /* CMSDK Timers */
-#define ARM_CMSDK_TIMER0
 #define ARM_CMSDK_TIMER1
+#define ARM_CMSDK_DUALTIMER
+
+/* Timer Peripherals are driven by APB System Core Clocks,
+ * defined in system_CMSDK_CM3DS.c
+ */
+#define TIMERS_INPUT_CLOCK_FREQ_HZ       25000000U
+
+/* mbed usec high-resolution ticker configuration */
+#define USEC_TIMER_DEV                   CMSDK_TIMER1_DEV
+
+#define usec_interval_irq_handler        TIMER1_IRQHandler
+#define USEC_INTERVAL_IRQ                TIMER1_IRQn
+
+/* The us ticker uses CMSDK Timer1, that does not have HW prescaler.
+ * The reported shift define is necessary for the software emulated
+ * prescaler behavior, so the ticker works as if it was ticking on a
+ * virtually slower frequency. The value 5 sets up the ticker to work
+ * properly in the specified frequency interval.
+ */
+#define USEC_TIMER_BIT_WIDTH    32U
+#define USEC_REPORTED_SHIFT     5U
+#define USEC_REPORTED_FREQ_HZ   (TIMERS_INPUT_CLOCK_FREQ_HZ >> \
+                                 USEC_REPORTED_SHIFT)
+#define USEC_REPORTED_BITS      (USEC_TIMER_BIT_WIDTH - USEC_REPORTED_SHIFT)
+
+/* mbed low power ticker configuration */
+#define LP_TIMER_DEV                     CMSDK_DUALTIMER_DEV
+
+#define lp_interval_irq_handler          DUALTIMER_IRQHandler
+#define LP_INTERVAL_IRQ                  DUALTIMER_IRQn
+
+/* The lp ticker a CMSDK Dual Timer that is capable of prescaling
+ * its input clock frequency by 256 at most. Having 25MHz as input
+ * frequency requires an additional slowing factor in order for the ticker
+ * to operate in the specified frequency interval, thus the effective
+ * prescaler value is going to be the sum of the HW and the virtual
+ * prescaler values.
+ */
+#define LP_TIMER_BIT_WIDTH            32U
+#define LP_TIMER_HW_PRESCALER         8U
+#define LP_REPORTED_SHIFT             1U
+#define LP_REPORTED_FREQ_HZ           (TIMERS_INPUT_CLOCK_FREQ_HZ >> \
+                                      (LP_TIMER_HW_PRESCALER+LP_REPORTED_SHIFT))
+#define LP_REPORTED_BITS              (LP_TIMER_BIT_WIDTH - LP_REPORTED_SHIFT)
+
+/* RTC PL031 */
+#define RTC_PL031
 
 /* ARM GPIO */
 #define ARM_GPIO0
@@ -51,7 +97,7 @@
 #define ARM_SPI4
 
 /* ARM UART */
-#define DEFAULT_UART_BAUDRATE  9600
+#define DEFAULT_UART_BAUDRATE  9600U
 #define ARM_UART0
 #define ARM_UART1
 #define ARM_UART2