/****************************************************************************
* arch/arm/src/str71x/str71x_timerisr.c
*
* Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <time.h>
#include <debug.h>
#include <nuttx/arch.h>
#include <arch/board/board.h>
#include "clock_internal.h"
#include "up_internal.h"
#include "up_arch.h"
#include "chip.h"
#include "str71x_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/* The desired timer interrupt frequency is provided by the definition
* CLK_TCK (see include/time.h). CLK_TCK defines the desired number of
* system clock ticks per second. That value is a user configurable setting
* that defaults to 100 (100 ticks per second = 10 MS interval).
*
* The best accuracy would be obtained by using the largest value in the
* the output compare register (OCAR), i.e., 0xffff = 65,535:
*/
#define MAX_OCAR 65535
/* In this case, the desired, maximum clocking would be MAX_TIM0CLK. For
* example if CLK_TCK is the default of 100Hz, then the ideal clocking for
* timer0 would be 6,553,500 */
#define MAX_TIM0CLK (MAX_OCAR * CLK_TCK)
/* The best divider then would be the one that reduces PCLK2 to MAX_TIM0CLK.
* Note that the following calculation forces an integer divisor to the next
* integer above the optimal. So, for example, if MAX_TIM0CLK is 6,553,500
* and PCLK2 is 32MHz, then ideal PCLK2_DIVIDER would be 4.88 but 5 is used
* instead. The value 5 would give an actual TIM0CLK of 6,400,000, less
* than the maximum.
*/
#if STR71X_PCLK2 > MAX_TIM0CLK
# define PCLK2_DIVIDER (((STR71X_PCLK2) + (MAX_TIM0CLK+1)) / MAX_TIM0CLK)
#else
# define PCLK2_DIVIDER (1)
#endif
#if PCLK2_DIVIDER > 255
# error "PCLK2 is too fast for any divisor"
#endif
/* Then we can get the actual OCAR value from the selected divider value.
* For example, if PCLK2 is 32MHz and PCLK2_DIVIDER is 5, then the actual
* TIM0CLK would 6,4000,000 and the final OCAR_VALUE would be 64,000.
*/
#define ACTUAL_TIM0CLK (STR71X_PCLK2 / PCLK2_DIVIDER)
#define OCAR_VALUE (ACTUAL_TIM0CLK / CLK_TCK)
#if OCAR_VALUE > 65535
# error "PCLK2 is too fast for the configured CLK_TCK"
#endif
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Function: up_timerisr
*
* Description:
* The timer ISR will perform a variety of services for various portions
* of the systems.
*
****************************************************************************/
int up_timerisr(int irq, uint32 *regs)
{
/* Process timer interrupt */
sched_process_timer();
return 0;
}
/****************************************************************************
* Function: up_timerinit
*
* Description:
* This function is called during start-up to initialize
* the timer interrupt.
*
****************************************************************************/
void up_timerinit(void)
{
uint16 cr1;
uint16 cr2;
/* Make sure that timer0 is disabled */
putreg16(0x0000, STR71X_TIMER0_CR1);
putreg16(0x0000, STR71X_TIMER0_CR2);
putreg16(0x0000, STR71X_TIMER0_SR);
/* Start The TIM0 Counter */
cr1 = STR71X_TIMERCR1_EN;
putreg16(cr1, STR71X_TIMER0_CR1);
/* Configure TIM0 so that it is clocked by the internal APB2 frequency (PCLK2)
* divided by the above prescaler value (1) -- versus an external Clock.
* -- Nothing to do because STR71X_TIMERCR1_ECKEN is already cleared.
*
*
* Select a divisor to reduce the frequency of clocking. This must be
* done so that the entire timer interval can fit in the 16-bit OCAR register.
* (see the discussion above).
*/
cr2 = PCLK2_DIVIDER;
putreg16(cr2, STR71X_TIMER0_CR2);
/* Setup output compare A for desired interrupt frequency. Note that
* the OCAE and OCBE bits are cleared and the pins are available for other
* functions.
*/
putreg16(OCAR_VALUE, STR71X_TIMER0_OCAR);
putreg16(0, STR71X_TIMER0_CNTR);
/* Enable TIM0 Output Compare A interrupt */
cr2 |= STR71X_TIMERCR2_OCAIE;
putreg16(cr2, STR71X_TIMER0_CR2);
/* Set the IRQ interrupt priority */
up_prioritize_irq(STR71X_IRQ_SYSTIMER, 1);
/* Attach the timer interrupt vector */
(void)irq_attach(STR71X_IRQ_SYSTIMER, (xcpt_t)up_timerisr);
/* And enable the timer interrupt */
up_enable_irq(STR71X_IRQ_SYSTIMER);
}
