init_cm3.c

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#include <cfg/compiler.h>
#include <cfg/cfg_proc.h> /* CONFIG_KERN_PREEMPT */
#include <kern/proc_p.h>
#include <cfg/debug.h>
#include <cpu/attr.h> /* PAUSE */
#include <cpu/irq.h> /* IRQ_DISABLE */
#include <cpu/types.h>
#include <drv/irq_cm3.h>
#include "switch_ctx_cm3.h"

#if CPU_CM3_LM3S
#include <drv/clock_lm3s.h>
#include <io/lm3s.h>
#elif CPU_CM3_STM32
#include <drv/clock_stm32.h>
#include <io/stm32.h>
#endif

extern size_t __text_end, __data_start, __data_end, __bss_start, __bss_end;

extern void __init2(void);

/* Architecture's entry point */
void __init2(void)
{
    /*
     * The main application expects IRQs disabled.
     */
    IRQ_DISABLE;

#if CPU_CM3_LM3S
    /*
     * PLL may not function properly at default LDO setting.
     *
     * Description:
     *
     * In designs that enable and use the PLL module, unstable device
     * behavior may occur with the LDO set at its default of 2.5 volts or
     * below (minimum of 2.25 volts). Designs that do not use the PLL
     * module are not affected.
     *
     * Workaround: Prior to enabling the PLL module, it is recommended that
     * the default LDO voltage setting of 2.5 V be adjusted to 2.75 V using
     * the LDO Power Control (LDOPCTL) register.
     *
     * Silicon Revision Affected: A1, A2
     *
     * See also: Stellaris LM3S1968 A2 Errata documentation.
     */
    if (REVISION_IS_A1 | REVISION_IS_A2)
        HWREG(SYSCTL_LDOPCTL) = SYSCTL_LDOPCTL_2_75V;
#endif
    /* Set the appropriate clocking configuration */
    clock_init();

    /* Initialize IRQ vector table in RAM */
    sysirq_init();

#if (CONFIG_KERN && CONFIG_KERN_PREEMPT)
    /*
     * Voluntary context switch handler.
     *
     * This software interrupt can always be triggered and must be
     * dispatched as soon as possible, thus we just disable IRQ priority
     * for it.
     */
    sysirq_setHandler(FAULT_SVCALL, svcall_handler);
    sysirq_setPriority(FAULT_SVCALL, IRQ_PRIO_MAX);
    /*
     * Preemptible context switch handler
     *
     * The priority of this IRQ must be the lowest priority in the system
     * in order to run last in the interrupt service routines' chain.
     */
    sysirq_setHandler(FAULT_PENDSV, pendsv_handler);
    sysirq_setPriority(FAULT_PENDSV, IRQ_PRIO_MIN);
#endif
}