[PATCH] device driver for the SGI system clock, mmtimer

SGI has been using this driver under Linux since 2001 but it was
never included in the upstream kernel. SuSE did include the patch for mmtimer
in SLES 9. The driver has been widely used for applications on the Altix
platform.

The timer hardware was designed around the multimedia timer specification by
Intel but to my knowledge only SGI has implemented that standard. The driver
was written by Jesse Barnes.

The second revision has interrupt support removed and was somewhat simplified
by removing one include file.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ia64/sn/kernel/setup.c

@@ -64,6 +64,8 @@ extern unsigned char acpi_kbd_controller_present;
 
 unsigned long sn_rtc_cycles_per_second;   
 
+EXPORT_SYMBOL(sn_rtc_cycles_per_second);
+
 partid_t sn_partid = -1;
 char sn_system_serial_number_string[128];
 u64 sn_partition_serial_number;

drivers/char/Kconfig

@@ -981,5 +981,13 @@ config HANGCHECK_TIMER
 	  out to lunch past a certain margin.  It can reboot the system
 	  or merely print a warning.
 
+config MMTIMER
+	tristate "MMTIMER Memory mapped RTC for SGI Altix"
+	depends on IA64_GENERIC || IA64_SGI_SN2
+	default y
+	help
+	  The mmtimer device allows direct userspace access to the
+	  Altix system timer.
+
 endmenu
 

drivers/char/Makefile

@@ -45,6 +45,7 @@ obj-$(CONFIG_RIO)		+= rio/ generic_serial.o
 obj-$(CONFIG_HVC_CONSOLE)	+= hvc_console.o hvsi.o
 obj-$(CONFIG_RAW_DRIVER)	+= raw.o
 obj-$(CONFIG_SGI_SNSC)		+= snsc.o
+obj-$(CONFIG_MMTIMER)		+= mmtimer.o
 obj-$(CONFIG_VIOCONS) += viocons.o
 obj-$(CONFIG_VIOTAPE)		+= viotape.o
 obj-$(CONFIG_HVCS)		+= hvcs.o

drivers/char/mmtimer.c

+/*
+ * Intel Multimedia Timer device implementation for SGI SN platforms.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2001-2003 Silicon Graphics, Inc.  All rights reserved.
+ *
+ * This driver implements a subset of the interface required by the
+ * IA-PC Multimedia Timers Draft Specification (rev. 0.97) from Intel.
+ *
+ * 11/01/01 - jbarnes - initial revision
+ * 9/10/04 - Christoph Lameter - remove interrupt support for kernel inclusion
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/ioctl.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/devfs_fs_kernel.h>
+#include <linux/mmtimer.h>
+#include <linux/miscdevice.h>
+#include <asm/uaccess.h>
+#include <asm/sn/addrs.h>
+#include <asm/sn/clksupport.h>
+
+MODULE_AUTHOR("Jesse Barnes <jbarnes@sgi.com>");
+MODULE_DESCRIPTION("Multimedia timer support");
+MODULE_LICENSE("GPL");
+
+#define RTC_BITS 55 /* 55 bits for this implementation */
+
+static int mmtimer_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg);
+static int mmtimer_mmap(struct file *file, struct vm_area_struct *vma);
+
+/*
+ * Period in femtoseconds (10^-15 s)
+ */
+static unsigned long mmtimer_femtoperiod = 0;
+
+static struct file_operations mmtimer_fops = {
+	.owner =	THIS_MODULE,
+	.mmap =		mmtimer_mmap,
+	.ioctl =	mmtimer_ioctl,
+};
+
+/**
+ * mmtimer_ioctl - ioctl interface for /dev/mmtimer
+ * @inode: inode of the device
+ * @file: file structure for the device
+ * @cmd: command to execute
+ * @arg: optional argument to command
+ *
+ * Executes the command specified by @cmd.  Returns 0 for success, <0 for failure.
+ * Valid commands are
+ *
+ * %MMTIMER_GETOFFSET - Should return the offset (relative to the start
+ * of the page where the registers are mapped) for the counter in question.
+ *
+ * %MMTIMER_GETRES - Returns the resolution of the clock in femto (10^-15)
+ * seconds
+ *
+ * %MMTIMER_GETFREQ - Copies the frequency of the clock in Hz to the address
+ * specified by @arg
+ *
+ * %MMTIMER_GETBITS - Returns the number of bits in the clock's counter
+ *
+ * %MMTIMER_MMAPAVAIL - Returns 1 if the registers can be mmap'd into userspace
+ *
+ * %MMTIMER_GETCOUNTER - Gets the current value in the counter and places it
+ * in the address specified by @arg.
+ */
+static int
+mmtimer_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
+{
+	int ret = 0;
+
+	switch (cmd) {
+	case MMTIMER_GETOFFSET:	/* offset of the counter */
+		/*
+		 * SN RTC registers are on their own 64k page
+		 */
+		if(PAGE_SIZE <= (1 << 16))
+			ret = (((long)RTC_COUNTER_ADDR) & (PAGE_SIZE-1)) / 8;
+		else
+			ret = -ENOSYS;
+		break;
+
+	case MMTIMER_GETRES: /* resolution of the clock in 10^-15 s */
+		if(copy_to_user((unsigned long *)arg, &mmtimer_femtoperiod, sizeof(unsigned long)))
+			return -EFAULT;
+		break;
+
+	case MMTIMER_GETFREQ: /* frequency in Hz */
+		if(copy_to_user((unsigned long *)arg, &sn_rtc_cycles_per_second, sizeof(unsigned long)))
+			return -EFAULT;
+		ret = 0;
+		break;
+
+	case MMTIMER_GETBITS: /* number of bits in the clock */
+		ret = RTC_BITS;
+		break;
+
+	case MMTIMER_MMAPAVAIL: /* can we mmap the clock into userspace? */
+		ret = (PAGE_SIZE <= (1 << 16)) ? 1 : 0;
+		break;
+
+	case MMTIMER_GETCOUNTER:
+		if(copy_to_user((unsigned long *)arg, RTC_COUNTER_ADDR, sizeof(unsigned long)))
+			return -EFAULT;
+		break;
+	default:
+		ret = -ENOSYS;
+		break;
+	}
+
+	return ret;
+}
+
+/**
+ * mmtimer_mmap - maps the clock's registers into userspace
+ * @file: file structure for the device
+ * @vma: VMA to map the registers into
+ *
+ * Calls remap_page_range() to map the clock's registers into
+ * the calling process' address space.
+ */
+static int
+mmtimer_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	unsigned long mmtimer_addr;
+
+	if (vma->vm_end - vma->vm_start != PAGE_SIZE)
+		return -EINVAL;
+
+	if (vma->vm_flags & VM_WRITE)
+		return -EPERM;
+
+	if (PAGE_SIZE > (1 << 16))
+		return -ENOSYS;
+
+	vma->vm_flags |= (VM_IO | VM_SHM | VM_LOCKED );
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+	mmtimer_addr = __pa(RTC_COUNTER_ADDR);
+	mmtimer_addr &= ~(PAGE_SIZE - 1);
+	mmtimer_addr &= 0xfffffffffffffffUL;
+
+	if (remap_page_range(vma, vma->vm_start, mmtimer_addr, PAGE_SIZE, vma->vm_page_prot)) {
+		printk(KERN_ERR "remap_page_range failed in mmtimer.c\n");
+		return -EAGAIN;
+	}
+
+	return 0;
+}
+
+static struct miscdevice mmtimer_miscdev = {
+	SGI_MMTIMER,
+	MMTIMER_NAME,
+	&mmtimer_fops
+};
+
+/**
+ * mmtimer_init - device initialization routine
+ *
+ * Does initial setup for the mmtimer device.
+ */
+static int __init
+mmtimer_init(void)
+{
+	/*
+	 * Sanity check the cycles/sec variable
+	 */
+	if (sn_rtc_cycles_per_second < 100000) {
+		printk(KERN_ERR "%s: unable to determine clock frequency\n", MMTIMER_NAME);
+		return -1;
+	}
+
+	mmtimer_femtoperiod = ((unsigned long)1E15 + sn_rtc_cycles_per_second / 2) /
+		sn_rtc_cycles_per_second;
+
+	strcpy(mmtimer_miscdev.devfs_name, MMTIMER_NAME);
+	if (misc_register(&mmtimer_miscdev)) {
+		printk(KERN_ERR "%s: failed to register device\n", MMTIMER_NAME);
+		return -1;
+	}
+
+	printk(KERN_INFO "%s: v%s, %ld MHz\n", MMTIMER_DESC, MMTIMER_VERSION, sn_rtc_cycles_per_second/(unsigned long)1E6);
+
+	return 0;
+}
+
+module_init(mmtimer_init);
+

include/linux/miscdevice.h

@@ -19,6 +19,7 @@
 #define SUN_OPENPROM_MINOR 139
 #define DMAPI_MINOR		140	/* DMAPI */
 #define NVRAM_MINOR 144
+#define SGI_MMTIMER        153
 #define STORE_QUEUE_MINOR	155
 #define I2O_MINOR 166
 #define MICROCODE_MINOR		184

include/linux/mmtimer.h

+/*
+ * Intel Multimedia Timer device interface
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2001-2003 Silicon Graphics, Inc.  All rights reserved.
+ *
+ * This file should define an interface compatible with the IA-PC Multimedia
+ * Timers Draft Specification (rev. 0.97) from Intel.  Note that some
+ * hardware may not be able to safely export its registers to userspace,
+ * so the ioctl interface should support all necessary functionality.
+ *
+ * 11/01/01 - jbarnes - initial revision
+ * 9/10/04 - Christoph Lameter - remove interrupt support
+ */
+
+#ifndef _LINUX_MMTIMER_H
+#define _LINUX_MMTIMER_H
+
+/* name of the device, usually in /dev */
+#define MMTIMER_NAME "mmtimer"
+#define MMTIMER_FULLNAME "/dev/mmtimer"
+#define MMTIMER_DESC "IA-PC Multimedia Timer"
+#define MMTIMER_VERSION "1.0"
+
+/*
+ * Breakdown of the ioctl's available.  An 'optional' next to the command
+ * indicates that supporting this command is optional, while 'required'
+ * commands must be implemented if conformance is desired.
+ *
+ * MMTIMER_GETOFFSET - optional
+ *   Should return the offset (relative to the start of the page where the
+ *   registers are mapped) for the counter in question.
+ *
+ * MMTIMER_GETRES - required
+ *   The resolution of the clock in femto (10^-15) seconds
+ *
+ * MMTIMER_GETFREQ - required
+ *   Frequency of the clock in Hz
+ *
+ * MMTIMER_GETBITS - required
+ *   Number of bits in the clock's counter
+ *
+ * MMTIMER_MMAPAVAIL - required
+ *   Returns nonzero if the registers can be mmap'd into userspace, 0 otherwise
+ *
+ * MMTIMER_GETCOUNTER - required
+ *   Gets the current value in the counter
+ */
+#define MMTIMER_IOCTL_BASE 'm'
+
+#define MMTIMER_GETOFFSET _IO(MMTIMER_IOCTL_BASE, 0)
+#define MMTIMER_GETRES _IOR(MMTIMER_IOCTL_BASE, 1, unsigned long)
+#define MMTIMER_GETFREQ _IOR(MMTIMER_IOCTL_BASE, 2, unsigned long)
+#define MMTIMER_GETBITS _IO(MMTIMER_IOCTL_BASE, 4)
+#define MMTIMER_MMAPAVAIL _IO(MMTIMER_IOCTL_BASE, 6)
+#define MMTIMER_GETCOUNTER _IOR(MMTIMER_IOCTL_BASE, 9, unsigned long)
+
+/*
+ * An mmtimer verification program.  WARNINGs are ok, but ERRORs indicate
+ * that the device doesn't fully support the interface defined here.
+ */
+#ifdef _MMTIMER_TEST_PROGRAM
+
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include <sys/ioctl.h>
+
+#include "mmtimer.h"
+
+int main(int argc, char *argv[])
+{
+	int result, fd;
+	unsigned long val = 0;
+	unsigned long i;
+
+	if((fd = open("/dev/"MMTIMER_NAME, O_RDONLY)) == -1) {
+		printf("failed to open /dev/%s", MMTIMER_NAME);
+		return 1;
+	}
+
+        /*
+         * Can we mmap in the counter?
+         */
+        if((result = ioctl(fd, MMTIMER_MMAPAVAIL, 0)) == 1) {
+                printf("mmap available\n");
+	        /* ... so try getting the offset for each clock */
+	        if((result = ioctl(fd, MMTIMER_GETOFFSET, 0)) != -ENOSYS)
+	                printf("offset: %d\n", result);
+	        else
+	                printf("WARNING: offset unavailable for clock\n");
+	}
+        else
+                printf("WARNING: mmap unavailable\n");
+
+	/*
+	 * Get the resolution in femtoseconds
+	 */
+        if((result = ioctl(fd, MMTIMER_GETRES, &val)) != -ENOSYS)
+                printf("resolution: %ld femtoseconds\n", val);
+        else
+                printf("ERROR: failed to get resolution\n");
+
+	/*
+	 * Get the frequency in Hz
+	 */
+        if((result = ioctl(fd, MMTIMER_GETFREQ, &val)) != -ENOSYS)
+		if(val < 10000000) /* less than 10 MHz? */
+			printf("ERROR: frequency only %ld MHz, should be >= 10 MHz\n", val/1000000);
+		else
+			printf("frequency: %ld MHz\n", val/1000000);
+        else
+                printf("ERROR: failed to get frequency\n");
+
+	/*
+	 * How many bits in the counter?
+	 */
+        if((result = ioctl(fd, MMTIMER_GETBITS, 0)) != -ENOSYS)
+                printf("bits in counter: %d\n", result);
+        else
+                printf("ERROR: can't get number of bits in counter\n");
+
+	if((result = ioctl(fd, MMTIMER_GETCOUNTER, &val)) != -ENOSYS)
+		printf("counter value: %ld\n", val);
+	else
+		printf("ERROR: can't get counter value\n");
+
+	return 0;
+}
+
+#endif /* _MMTIMER_TEST_PROGRM */
+
+#endif /* _LINUX_MMTIMER_H */