interrupt_latency_mediaengine.c.txt

这是《嵌入式linux－硬件、软件与接口》一书对应的所有linux方面实例的源代码

/*
 * interrupt_latency_mediaengine v1.1 12/10/02
 * www.embeddedlinuxinterfacing.com
 *
 * The original location of this code is
 * http://www.embeddedlinuxinterfacing.com/chapters/11/
 *
 * Copyright (C) 2001 by Craig Hollabaugh
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

/*
 * interrupt_latency_mediaengine.c is based on procfs_example.c by Erik Mouw.
 * For more information, please see, The Linux Kernel Procfs Guide, Erik Mouw
 * http://kernelnewbies.org/documents/kdoc/procfs-guide/lkprocfsguide.html
 */

/*
arm-linux-gcc -O2 -D__KERNEL__ -DMODULE -I/usr/src/arm-linux/include -c interrupt_latency_mediaengine.c -o /tftpboot/arm-rootfs/tmp/interrupt_latency_mediaengine.o
*/

/* interrupt_latency_mediaengine.c module
 * This module measures instantanous interrupt latency of the MediaEngine
 * using GPIO01. Configure the GRER for GPIO01 rising edge interrupt
 * generation. Setting GPIO01 as an output then setting GPIO01 causes a
 * rising edge that generates the interrupt. GRER is set by ARM kernel
 * code, therefore just setting the register itself is not enough. Use
 * the set_GPIO_IRQ_edge  ARM-only function. See kernel source for more info.
 *
 * After module insertion, reading /proc/interrupt_latency will assert GPIO01
 * generating the interrupt. The interrupt handler will deassert this signal.
 * View on scope. An interrupt counter is included to help debug noisy a
 * interrupt line.
 */

/* v1.1 
 * a. Moved GPIO01 as output after set_GPIO_IRQ_edge, set_GPIO_IRQ_edge clears the gpdr bit in 2.4.17
 * b. Moved the GPIO01 as output below where the original gpdr setting is actually read
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/proc_fs.h>

#include <asm/io.h>

#define MODULE_VERSION "1.0"
#define MODULE_NAME "interrupt_latency_mediaengine"

/* see 9.1.1.1 Intel StrongARM SA-1110 Microprocessor Developer's Manual */
/* these are also defined in arch SA-1100.h but differently*/
#define GPIO         0x90040000 /* GPIO registers base address */
#define GPLR_OFFSET  0x00
#define GPDR_OFFSET  0x04
#define GPSR_OFFSET  0x08
#define GPCR_OFFSET  0x0C
#define GAFR_OFFSET  0x1C
#define GRER_OFFSET  0x10
#define GFER_OFFSET  0x14
#define GEDR_OFFSET  0x18
#define GPIOLEN      0x20
#define GPIO01       0x00000002

#define IC           0x90050000 /* Interrupt controller regstr base address */
#define ICIP_OFFSET  0x00
#define ICMR_OFFSET  0x04
#define ICLR_OFFSET  0x08
#define ICFP_OFFSET  0x10
#define ICLEN        0x20

static void *ic_base, *gpio_base;
unsigned long int gpdr, gafr, grer;

int interruptcount = 0;
struct timeval tv1, tv2;

#define INTERRUPT 1

static struct proc_dir_entry *interrupt_latency_file;

/*
 * function interrupt_interrupt_latency
 * This function is the interrupt handler for interrupt 1. It sets the tv2
 * structure using do_gettimeofday. It then clears GPIO01.
 */
void interrupt_interrupt_latency(int irq, void *dev_id, struct pt_regs *regs)
{
  do_gettimeofday(&tv2);
  writel(GPIO01, gpio_base + GPCR_OFFSET); /* deassert the interrupt signal */
  interruptcount++;
}

/*
 * function proc_read_interrupt_latency
 * The kernel executes this function when a read operation occurs on
 * /proc/interrupt_latency. This function sets the tv1 structure. It asserts
 * GPIO01 which should immediately cause interrupt 1 to occur. The handler
 * records tv2 and deasserts GPIO01. This function returns the time
 * differential between tv2 and tv1.
 */
static int proc_read_interrupt_latency(char *page, char **start, off_t off,
                                       int count, int *eof, void *data)
{
  int len;

  do_gettimeofday(&tv1);
  writel(GPIO01, gpio_base + GPSR_OFFSET); /* assert the interrupt signal */


 len = sprintf(page,"Start %9i.%06i\nFinish %9i.%06i\nLatency %6i\nCount%i\n",
                      (int) tv1.tv_sec, (int) tv1.tv_usec,
                      (int) tv2.tv_sec, (int) tv2.tv_usec,
                      (int) (tv2.tv_usec - tv1.tv_usec),
                      interruptcount);

  return len;
}

/*
 * function init_interrupt_latency
 * This function creates the /proc directory entry interrupt_latency. It
 * requests interrupt 1 from Linux then configures the interrupt controller.
 */
static int __init init_interrupt_latency(void)
{
  unsigned long r;
  int rv = 0;

  interrupt_latency_file = create_proc_entry("interrupt_latency", 0444, NULL);
  if(interrupt_latency_file == NULL) {
    return -ENOMEM;
  }

  interrupt_latency_file->data = NULL;
  interrupt_latency_file->read_proc = &proc_read_interrupt_latency;
  interrupt_latency_file->write_proc = NULL;
  interrupt_latency_file->owner = THIS_MODULE;

  ic_base = ioremap_nocache(IC,ICLEN);
  printk("ic_base       = 0x%08X\n",ic_base);


  /* request interrupt from linux */
  rv = request_irq(INTERRUPT, interrupt_interrupt_latency, 0,
                   "interrupt_latency",NULL);
  if ( rv ) {
    printk("Can't get interrupt %d\n", INTERRUPT);
    goto no_interrupt_latency;
  }

  /* print out interrupt controller status bits */
  r = readl(ic_base + ICIP_OFFSET);
  printk("ICIP          = 0x%08X\n",r);
  r = readl(ic_base + ICMR_OFFSET);
  printk("ICMR          = 0x%08X\n",r); /* bit is set here for INT1 */
  r = readl(ic_base + ICLR_OFFSET);
  printk("ICLR          = 0x%08X\n",r);
  r = readl(ic_base + ICFP_OFFSET);
  printk("ICFP          = 0x%08X\n",r);


  /* get GPIO base for register changing */
  gpio_base = ioremap_nocache(GPIO,GPIOLEN);
  printk("\ngpio_base     = 0x%08X\n",gpio_base);

  gpdr = readl(gpio_base + GPDR_OFFSET); /* preserve the gpdr bits */
  printk("GPDR          = 0x%08X\n",gpdr);

  gafr = readl(gpio_base + GAFR_OFFSET); /* preserve the gafr bits */
  printk("GAFR          = 0x%08X\n",gafr);

  r = readl(gpio_base + GPLR_OFFSET);
  printk("GPLR          = 0x%08X\n",r);

  grer = readl(gpio_base + GRER_OFFSET); /* preserve the grer bits */
  printk("GRER          = 0x%08X\n",grer);

/* use ARM-only Linux function requesting edge int */
  set_GPIO_IRQ_edge(GPIO01, GPIO_RISING_EDGE);
  printk("set_GPIO_IRQ_edge\n");

/* set GPIO01 to have rising edge int */
  writel(grer | GPIO01, gpio_base + GRER_OFFSET);  

/* configuring GPIO01 as output */
/* set GPIO01 as output */
  writel(gpdr |  GPIO01, gpio_base + GPDR_OFFSET);

/* set GPIO01 with no alt function */
  writel(gafr & ~GPIO01, gpio_base + GAFR_OFFSET);

  writel(GPIO01             , gpio_base + GPCR_OFFSET);  /* clear GPIO01 */
 
  r = readl(gpio_base + GPDR_OFFSET); 
  printk("GPDR          = 0x%08X\n",r);

  r = readl(gpio_base + GAFR_OFFSET); 
  printk("GAFR          = 0x%08X\n",r);

  r = readl(gpio_base + GRER_OFFSET);
  printk("GRER          = 0x%08X\n",r);

  r = readl(gpio_base + GFER_OFFSET);
  printk("GFER          = 0x%08X\n",r);

  r = readl(gpio_base + GEDR_OFFSET);
  printk("GEDR          = 0x%08X\n",r);

  /* everything initialized */
  printk(KERN_INFO "%s %s initialized\n",MODULE_NAME, MODULE_VERSION);
  return 0;

no_interrupt_latency:
  remove_proc_entry("interrupt_latency", NULL);
}


/*
 * function cleanup_interrupt_latency
 * This function frees interrupt 1,  restores registers, then removes the
 * /proc directory entry interrupt_latency.
 */
static void __exit cleanup_interrupt_latency(void)
{
  free_irq(INTERRUPT,NULL); /* free the interrupt */

  writel(gpdr, gpio_base + GPDR_OFFSET);  /* restore gpdr */
  writel(gafr, gpio_base + GAFR_OFFSET);  /* restore gafr */
  writel(grer, gpio_base + GRER_OFFSET);  /* restore grer */

  iounmap(ic_base);
  iounmap(gpio_base);

  remove_proc_entry("interrupt_latency", NULL);

  printk(KERN_INFO "%s %s removed\n", MODULE_NAME, MODULE_VERSION);
}

module_init(init_interrupt_latency);
module_exit(cleanup_interrupt_latency);

MODULE_AUTHOR("Craig Hollabaugh");
MODULE_DESCRIPTION("interrupt_latency proc module");

EXPORT_NO_SYMBOLS;