[arm-m] add simple systick driver

arch/arm/arm-m/arch.c

@@ -75,6 +75,9 @@ void arch_early_init(void)
 	/* set the svc and pendsv priority level to pretty low */
 	SCB->SHP[11-4] = cm3_lowest_priority();
 	SCB->SHP[14-4] = cm3_lowest_priority();
+
+	/* initialize the systick mechanism */
+	cm3_systick_init();
 }
 
 void arch_init(void)

arch/arm/arm-m/exceptions.c

@@ -85,7 +85,8 @@ void _usagefault(void)
 	halt();
 }
 
-void _systick(void)
+/* systick handler */
+void __WEAK _systick(void)
 {
 	printf("systick\n");
 	halt();

arch/arm/arm-m/include/arch/arm/cm3.h

@@ -106,5 +106,11 @@ static __ALWAYS_INLINE inline void cm3_trigger_preempt(void)
 	SCB->ICSR |= SCB_ICSR_PENDSVSET_Msk;
 }
 
+/* systick */
+void cm3_systick_init(void);
+void cm3_systick_set_periodic(uint32_t systick_clk_freq, time_t period);
+void cm3_systick_cancel_periodic(void);
+/* extern void _systick(void); // override this */
+
 #endif
 

arch/arm/arm-m/systick.c

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2012 Travis Geiselbrecht
+ *
+ * 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.
+ */
+#include <sys/types.h>
+#include <string.h>
+#include <stdlib.h>
+#include <debug.h>
+#include <kernel/thread.h>
+#include <arch/arm.h>
+#include <arch/arm/cm3.h>
+
+#define LOCAL_TRACE 0
+
+void cm3_systick_init(void)
+{
+	NVIC_SetPriority(SysTick_IRQn, cm3_medium_priority());
+}
+
+void cm3_systick_set_periodic(uint32_t systick_clk_freq, time_t period)
+{
+	LTRACEF("clk_freq %u, period %u\n", systick_clk_freq, period);
+
+	uint32_t ticks = ((uint64_t)systick_clk_freq) / (1000 / period);
+	LTRACEF("ticks %d\n", ticks);
+
+	SysTick->LOAD = (ticks & SysTick_LOAD_RELOAD_Msk) - 1;
+	SysTick->VAL = 0;
+	SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_TICKINT_Msk | SysTick_CTRL_ENABLE_Msk;
+}
+
+void cm3_systick_cancel_periodic(void)
+{
+	SysTick->CTRL &= ~SysTick_CTRL_ENABLE_Msk;
+}
+

arch/arm/rules.mk

@@ -126,6 +126,7 @@ OBJS += \
 	$(LOCAL_DIR)/arm-m/start.o \
 	$(LOCAL_DIR)/arm-m/exceptions.o \
 	$(LOCAL_DIR)/arm-m/thread.o \
+	$(LOCAL_DIR)/arm-m/systick.o \
 	$(LOCAL_DIR)/arm-m/CMSIS/CM3/CoreSupport/core_cm3.o
 
 INCLUDES += \