CM3DS: switch us_ticker HAL to the tick domain

This commit changes the conversion function to do all the calculation
inside the HAL in ticks instead of microseconds.
The conversion will be done in Mbed OS side.
As SystemCoreClock is not a constant, it can not be used to initialise
the ticker_info_t structure.

Change-Id: I8fd4bf20dc5be8b965aca45f800a631275ccc724
Signed-off-by: Hugues de Valon <[email protected]>

Author: hug-dev

targets/TARGET_ARM_SSG/TARGET_CM3DS_MPS2/us_ticker.c

@@ -23,30 +23,37 @@
 #include "us_ticker_api.h"
 #include "platform_devices.h"
 
+/*
+ * The CMSDK Ticker counts on 32 bits.
+ */
+#define CMSDK_TICKER_COUNTER_BITS 32U
+
 /**
- * \brief Convert clocks to us
+ * \brief Pass-through function to make the US ticker HAL only work in the tick
+ *        domain. This function is needed by the CMSDK Ticker layer.
  *
- * \param[in] tick Number of clocks
+ * \param[in] tick Number of clock ticks
  *
- * \return Number of usec, relative to the timer frequency,
- *         that a given ammount of ticks equates to.
+ * \return The number of ticks given.
  */
 static uint32_t convert_tick_to_us(uint32_t tick)
 {
-    return (tick / (SystemCoreClock / SEC_TO_USEC_MULTIPLIER));
+    /* Work only in the tick domain. */
+    return tick;
 }
 
 /**
- * \brief Convert us to clock ticks
+ * \brief Pass-through function to make the US ticker HAL only work in the tick
+ *        domain. This function is needed by the CMSDK Ticker layer.
  *
- * \param[in] us Time to convert to clock ticks
+ * \param[in] us Number of us
  *
- * \return Number of clock ticks relative to the timer frequency,
- *         that a given period of usec equates to.
+ * \return The number of us given.
  */
 static uint32_t convert_us_to_tick(uint32_t us)
 {
-    return (us * (SystemCoreClock / SEC_TO_USEC_MULTIPLIER));
+    /* Work only in the tick domain. */
+    return us;
 }
 
 static const struct tick_cfg_t cfg =
@@ -109,3 +116,18 @@ void TIMER0_IRQHandler(void)
 {
     cmsdk_ticker_irq_handler(&timer_data);
 }
+
+const ticker_info_t* us_ticker_get_info(void)
+{
+    static ticker_info_t us_ticker_info = {
+        .bits = CMSDK_TICKER_COUNTER_BITS
+    };
+
+    /*
+     * SystemCoreClock is not a constant so it cannot be used to initialize the
+     * ticker_info_t structure.
+     */
+    us_ticker_info.frequency = SystemCoreClock;
+
+    return &us_ticker_info;
+}