/****************************************************************************
* arch/sh/src/sh1/sh1_timerisr.c
*
* Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 <stdint.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"
/****************************************************************************
* 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).
*
* ITU1 operates in periodic timer mode. TCNT counts up until it matches
* the value of GRA0, then an interrupt is generated. Two values must be
* computed:
*
* (1) The divider that determines the rate at which TCNT increments, and
* (2) The value of GRA0 that cause the interrupt to occur.
*
* These must be selected so that the frequency of interrupt generation is
* CLK_TCK. Ideally, we would like to use the full range of GRA0 for better
* timing acuracy:
*/
#define DESIRED_GRA0 65535
/* The ideal divider would be one that generates exactly 65535 ticks in
* 1/CLK_TCK seconds. For example, if SH1_CLOCK is 10MHz and CLK_TCK is
* 100, then the ideal divider must be less greater than or equal to:
*
* (10,000,000 / CLK_TCK) / 65535 = 1.525
*
* The actual selected divider would then have to be 2, resulting in a
* counting rate of 5,000,0000 and a GRA0 setting of 50,000.
*/
#define SYSCLKS_PER_TICK ((SH1_CLOCK + (CLK_TCK-1))/ CLK_TCK)
#define DESIRED_DIVIDER ((SYSCLKS_PER_TICK + (DESIRED_GRA0-1))/ DESIRED_GRA0)
#if (DESIRED_DIVIDER <= 1)
# define SYSCLK_DIVIDER 1
# define SH1_ITUTCR_DIV SH1_ITUTCR_DIV1
#elif (DESIRED_DIVIDER <= 2)
# define SYSCLK_DIVIDER 2
# define SH1_ITUTCR_DIV SH1_ITUTCR_DIV2
#elif (DESIRED_DIVIDER <= 4)
# define SYSCLK_DIVIDER 4
# define SH1_ITUTCR_DIV SH1_ITUTCR_DIV4
#elif (DESIRED_DIVIDER <= 8)
# define SYSCLK_DIVIDER 8
# define SH1_ITUTCR_DIV SH1_ITUTCR_DIV8
#else
# error "No divider is available for this system clock"
#endif
/* The TCNT will then increment at the following rate: */
#define TCNT_CLOCK ((SH1_CLOCK + (SYSCLK_DIVIDER/2))/ SYSCLK_DIVIDER)
/* And the value of GRA0 that generates at CLK_TCK ticks per second is: */
#define TCNT_PER_TICK ((TCNT_CLOCK + (CLK_TCK-1))/ CLK_TCK)
/****************************************************************************
* 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_t *regs)
{
uint8_t reg8;
/* Process timer interrupt */
sched_process_timer();
/* Clear ITU0 interrupt status flag */
reg8 = getreg8(SH1_ITU0_TSR);
reg8 &= ~SH1_ITUTSR_IMFA;
putreg8(reg8, SH1_ITU0_TSR);
return 0;
}
/****************************************************************************
* Function: up_timerinit
*
* Description:
* This function is called during start-up to initialize
* the timer interrupt.
*
****************************************************************************/
void up_timerinit(void)
{
uint8_t reg8;
/* Clear timer counter 0 */
putreg16(0, SH1_ITU0_TCNT);
/* Set the GRA0 match value. The interrupt will be generated when TNCT
* increments to this value
*/
putreg16(TCNT_PER_TICK, SH1_ITU0_GRA);
/* Set the timer control register. TCNT cleared by FRA */
putreg8(SH1_ITUTCR_CGRA|SH1_ITUTCR_DIV, SH1_ITU0_TCR);
/* Set the timer I/O control register */
putreg8(0, SH1_ITU0_TIOR); /* GRA used but with no inputs/output pins */
/* Make sure that all status flags are clear */
putreg8(0, SH1_ITU0_TSR);
/* Attach the IMIA0 IRQ */
irq_attach(SH1_SYSTIMER_IRQ, (xcpt_t)up_timerisr);
/* Enable interrupts on GRA compare match */
putreg8(SH1_ITUTIER_IMIEA, SH1_ITU0_TIER);
/* Set the interrupt priority */
up_prioritize_irq(SH1_SYSTIMER_IRQ, 7); /* Set ITU priority midway */
/* Start the timer */
reg8 = getreg8(SH1_ITU_TSTR);
reg8 |= SH1_ITUTSTR_STR0; /* Enable TCNT0 */
putreg8(reg8, SH1_ITU_TSTR); /* TCNT0 is counting */
}
