//-------------------------------------------------------------------
//	timing.c
//
//	This example employs the x86 processor's TimeStamp Counter 
//	to obtain a measurement of the cpu's elapsed clock-cycles.
//
//	NOTE: Written and tested with Linux kernel version 2.6.22.5.
//
//	programmer: ALLAN CRUSE
//	written on: 05 FEB 2008
//-------------------------------------------------------------------

#include <linux/module.h>	// for init_module() 
#include <linux/proc_fs.h>	// for create_proc_info_entry() 
#include <linux/pci.h>		// for pci_get_device()

#define VENDOR_ID	0x8086	// Intel Corporation
#define DEVICE_ID	0x109A	// 82573L controller
//#define DEVICE_ID	0x10B9	// 82572EI controller

enum { E1000_STATUS = 0x0008, };

char modname[] = "timing";
struct pci_dev	*devp;
unsigned int	mmio_base;
unsigned int	mmio_size;
void		*io;
unsigned long long  stamp1;
unsigned long long  stamp2;
unsigned long long  cycles;


int my_get_info( char *buf, char **start, off_t off, int count )
{
	int	status, len = 0;

	// disable interrupts and save TimeStamp Counter's initial value
	asm(" cli \n rdtsc ");
	asm(" mov %%eax, stamp1 \n mov %%edx, stamp1+4 " : : : "ax", "dx" );

	// perform a NIC register-access
	status = ioread32( io + E1000_STATUS );

	// save TimeStamp Counter's final value and reenable interrupts
	asm(" rdtsc \n sti ");
	asm(" mov %%eax, stamp2 \n mov %%edx, stamp2+4 " : : : "ax", "dx" );

	// subtract to get the number of elapsed cpu clock-cycles
	cycles = stamp2 - stamp1;

	// display the number of elapsed cpu clock-cycles
	len += sprintf( buf+len, "\n Elapsed cpu-cycles = %llu\n", cycles );
	len += sprintf( buf+len, "\n" );

	return	len;
}


static int __init timing_init( void )
{
	printk( "<1>\nInstalling \'%s\' module\n", modname );

	devp = pci_get_device( VENDOR_ID, DEVICE_ID, NULL );
	if ( !devp ) return -ENODEV;

	mmio_base = pci_resource_start( devp, 0 );
	mmio_size = pci_resource_len( devp, 0 );
	io = ioremap_nocache( mmio_base, mmio_size );
	if ( !io ) return -ENOSPC;

	create_proc_info_entry( modname, 0, NULL, my_get_info );
	return	0;  //SUCCESS
}


static void __exit timing_exit(void )
{
	remove_proc_entry( modname, NULL );
	iounmap( io );

	printk( "<1>Removing \'%s\' module\n", modname );
}

module_init( timing_init );
module_exit( timing_exit );
MODULE_LICENSE("GPL");