For many MIPS boards that start to use CONFIG_NEW_TIME_C, two rtc operations
are implemented, rtc_get_time() and rtc_set_time().
It is possible to write a simple generic RTC driver that is based on
these two ops and can do simple RTC read&write ops.
In other words, with such a driver, once you implemented rtc_get_time()
and rtc_set_time(), which is required by the kernel anyway, you will
automatically get a free /dev/rtc/ driver.
This is the idea behind the generic MIPS rtc driver. See the patch below.
Right now the feature is rather limited, due to the thin abstraction
we are having with rtc ops. But apparently the implementation is good
enough to make hwclock program happy.
Any comments?
Jun
/*
* A simple generic Real Time Clock interface for Linux/MIPS
*
* Copyright (C) 1996 Paul Gortmaker
*
* Copyright (C) 2001 Monta Vista Software
* Author Jun Sun, jsun@mvista.com or jsun@junsun.net
*
* This is a simple generic RTC driver for MIPS boards configured
* with CONFIG_NEW_TIME_C. For now, it makes use of the two
* abstract kernel RTC functions introduced in include/asm-mips/time.h:
*
* extern unsigned long (*rtc_get_time)(void);
* extern int (*rtc_set_time)(unsigned long);
*
* It uses the same protocol as the original drivers/char/rtc.c driver,
* but only implements two ioctls: RTC_RD_TIME and RTC_SET_TIME.
*
* TODO :
*
* 1. we can extend the null rtc ops defined in arch/mips/time.c to
* at least record the elapsed time (by recording/checking jiffies)
* This way RTC_RD_TIME and RTC_SET_TIME will make more sense.
* (Maybe not. A machine without a real RTC is broken anymore.
* Just a thought.)
*
* 2. If we make use of timer bh, we can emulate many RTC functions
* such as RTC alarm interrupt, periodic interrupts, etc.
*
* 3. It is possible to extend the kernel RTC abstractions to more
* than two functions, so that perhaps we can implement more
* full-featured RTC driver and also have a better abstraction
* to support more RTC hardware than the original RTC driver.
* It needs to be done very carefully.
*
* Change Log :
* v1.0 - [jsun] initial version
*/
diff -Nru linux/Documentation/Configure.help.orig linux/Documentation/Configure.help
--- linux/Documentation/Configure.help.orig Sat Nov 10 18:48:51 2001
+++ linux/Documentation/Configure.help Sat Nov 10 22:58:23 2001
@@ -15163,6 +15163,17 @@
#EFI Real Time Clock Services
#CONFIG_EFI_RTC
+Generic MIPS RTC Support
+CONFIG_MIPS_RTC
+
+ If your machine is a MIPS machine, this option provides a simple,
+ generic RTC driver for /dev/rtc device. It only implements two IOCTL
+ operations of the standard PC RTC driver: RTC_RD_TIME and RTC_SET_TIME.
+ It is sufficient to run hwclock program.
+
+ You should say Y here if there is no machine-specific RTC driver for your
+ MIPS machine but you do want a simple RTC driver for your RTC device.
+
Tadpole ANA H8 Support
CONFIG_H8
The Hitachi H8/337 is a microcontroller used to deal with the power
diff -Nru linux/drivers/char/Config.in.orig linux/drivers/char/Config.in
--- linux/drivers/char/Config.in.orig Sat Nov 10 18:49:31 2001
+++ linux/drivers/char/Config.in Sat Nov 10 22:48:27 2001
@@ -194,6 +194,9 @@
if [ "$CONFIG_OBSOLETE" = "y" -a "$CONFIG_ALPHA_BOOK1" = "y" ]; then
bool 'Tadpole ANA H8 Support' CONFIG_H8
fi
+if [ "$CONFIG_MIPS" = "y" -a "$CONFIG_NEW_TIME_C" = "y" ]; then
+ tristate 'Generic MIPS RTC Support' CONFIG_MIPS_RTC
+fi
tristate 'Double Talk PC internal speech card support' CONFIG_DTLK
tristate 'Siemens R3964 line discipline' CONFIG_R3964
diff -Nru linux/drivers/char/Makefile.orig linux/drivers/char/Makefile
--- linux/drivers/char/Makefile.orig Sat Nov 10 18:49:31 2001
+++ linux/drivers/char/Makefile Sat Nov 10 21:54:00 2001
@@ -194,6 +194,7 @@
obj-$(CONFIG_PC110_PAD) += pc110pad.o
obj-$(CONFIG_RTC) += rtc.o
obj-$(CONFIG_EFI_RTC) += efirtc.o
+obj-$(CONFIG_MIPS_RTC) += mips_rtc.o
ifeq ($(CONFIG_PPC),)
obj-$(CONFIG_NVRAM) += nvram.o
endif
diff -Nru linux/drivers/char/mips_rtc.c.orig linux/drivers/char/mips_rtc.c
--- linux/drivers/char/mips_rtc.c.orig Sat Nov 10 21:03:02 2001
+++ linux/drivers/char/mips_rtc.c Sat Nov 10 23:10:39 2001
@@ -0,0 +1,221 @@
+/*
+ * A simple generic Real Time Clock interface for Linux/MIPS
+ *
+ * Copyright (C) 1996 Paul Gortmaker
+ *
+ * Copyright (C) 2001 Monta Vista Software
+ * Author Jun Sun, jsun@mvista.com or jsun@junsun.net
+ *
+ * This is a simple generic RTC driver for MIPS boards configured
+ * with CONFIG_NEW_TIME_C. For now, it makes use of the two
+ * abstract kernel RTC functions introduced in include/asm-mips/time.h:
+ *
+ * extern unsigned long (*rtc_get_time)(void);
+ * extern int (*rtc_set_time)(unsigned long);
+ *
+ * It uses the same protocol as the original drivers/char/rtc.c driver,
+ * but only implements two ioctls: RTC_RD_TIME and RTC_SET_TIME.
+ *
+ * TODO :
+ *
+ * 1. we can extend the null rtc ops defined in arch/mips/time.c to
+ * at least record the elapsed time (by recording/checking jiffies)
+ * This way RTC_ALM_READ and RTC_ALM_SET will make more sense.
+ * (Maybe not. A machine without a real RTC is broken anymore.
+ * Just a thought.)
+ *
+ * 2. If we make use of timer bh, we can emulate many RTC functions
+ * such as RTC alarm interrupt, periodic interrupts, etc.
+ *
+ * 3. It is possible to extend the kernel RTC abstractions to more
+ * than two functions, so that perhaps we can implement more
+ * full-featured RTC driver and also have a better abstraction
+ * to support more RTC hardware than the original RTC driver.
+ * It needs to be done very carefully.
+ *
+ * Change Log :
+ * v1.0 - [jsun] initial version
+ */
+
+#define RTC_VERSION "1.0"
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/miscdevice.h>
+#include <linux/fcntl.h>
+#include <linux/init.h>
+#include <linux/poll.h>
+#include <linux/proc_fs.h>
+#include <linux/spinlock.h>
+
+#include <asm/io.h>
+#include <asm/uaccess.h>
+#include <asm/system.h>
+
+/*
+ * Check machine
+ */
+#if !defined(CONFIG_MIPS) || !defined(CONFIG_NEW_TIME_C)
+#error "This driver is for MIPS machines with CONFIG_NEW_TIME_C defined"
+#endif
+
+#include <asm/time.h>
+
+static unsigned long rtc_status = 0; /* bitmapped status byte. */
+
+static int rtc_read_proc(char *page, char **start, off_t off,
+ int count, int *eof, void *data);
+
+
+#define RTC_IS_OPEN 0x01 /* means /dev/rtc is in use */
+
+static spinlock_t rtc_lock;
+
+static int
+rtc_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ struct rtc_time rtc_tm;
+ ulong curr_time;
+
+ switch (cmd) {
+ case RTC_RD_TIME: /* Read the time/date from RTC */
+ curr_time = rtc_get_time();
+ to_tm(curr_time, &rtc_tm);
+ rtc_tm.tm_year -= 1900;
+ return copy_to_user((void *) arg, &rtc_tm, sizeof(rtc_tm)) ?
+ -EFAULT : 0;
+ case RTC_SET_TIME: /* Set the RTC */
+ if (!capable(CAP_SYS_TIME))
+ return -EACCES;
+
+ if (copy_from_user(&rtc_tm,
+ (struct rtc_time *) arg,
+ sizeof(struct rtc_time)))
+ return -EFAULT;
+
+ curr_time = mktime(rtc_tm.tm_year + 1900,
+ rtc_tm.tm_mon + 1, /* tm_mon starts from 0 */
+ rtc_tm.tm_mday,
+ rtc_tm.tm_hour,
+ rtc_tm.tm_min,
+ rtc_tm.tm_sec);
+ return rtc_set_time(curr_time);
+ default:
+ return -EINVAL;
+ }
+}
+
+/* We use rtc_lock to protect against concurrent opens. So the BKL is not
+ * needed here. Or anywhere else in this driver. */
+static int rtc_open(struct inode *inode, struct file *file)
+{
+ spin_lock_irq(&rtc_lock);
+
+ if (rtc_status & RTC_IS_OPEN) {
+ spin_unlock_irq(&rtc_lock);
+ return -EBUSY;
+ }
+
+ rtc_status |= RTC_IS_OPEN;
+
+ spin_unlock_irq(&rtc_lock);
+ return 0;
+}
+
+static int rtc_release(struct inode *inode, struct file *file)
+{
+ spin_lock_irq(&rtc_lock);
+ rtc_status &= ~RTC_IS_OPEN;
+ spin_unlock_irq(&rtc_lock);
+ return 0;
+}
+
+/*
+ * The various file operations we support.
+ */
+
+static struct file_operations rtc_fops = {
+ owner:THIS_MODULE,
+ llseek:no_llseek,
+ ioctl:rtc_ioctl,
+ open:rtc_open,
+ release:rtc_release,
+};
+
+static struct miscdevice rtc_dev = {
+ RTC_MINOR,
+ "rtc",
+ &rtc_fops
+};
+
+static int __init rtc_init(void)
+{
+
+ misc_register(&rtc_dev);
+ create_proc_read_entry("driver/rtc", 0, 0, rtc_read_proc, NULL);
+
+ printk(KERN_INFO "Generic MIPS RTC Driver v" RTC_VERSION "\n");
+
+ return 0;
+}
+
+static void __exit rtc_exit(void)
+{
+ remove_proc_entry("driver/rtc", NULL);
+ misc_deregister(&rtc_dev);
+
+}
+
+module_init(rtc_init);
+module_exit(rtc_exit);
+EXPORT_NO_SYMBOLS;
+
+/*
+ * Info exported via "/proc/driver/rtc".
+ */
+
+static int rtc_proc_output(char *buf)
+{
+ char *p;
+ struct rtc_time tm;
+ unsigned long curr_time;
+
+ curr_time = rtc_get_time();
+ to_tm(curr_time, &tm);
+
+ p = buf;
+
+ /*
+ * There is no way to tell if the luser has the RTC set for local
+ * time or for Universal Standard Time (GMT). Probably local though.
+ */
+ p += sprintf(p,
+ "rtc_time\t: %02d:%02d:%02d\n"
+ "rtc_date\t: %04d-%02d-%02d\n"
+ "rtc_epoch\t: %04lu\n",
+ tm.tm_hour, tm.tm_min, tm.tm_sec,
+ tm.tm_year, tm.tm_mon + 1, tm.tm_mday, 0L);
+
+ return p - buf;
+}
+
+static int rtc_read_proc(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len = rtc_proc_output(page);
+ if (len <= off + count)
+ *eof = 1;
+ *start = page + off;
+ len -= off;
+ if (len > count)
+ len = count;
+ if (len < 0)
+ len = 0;
+ return len;
+}
+
+MODULE_AUTHOR("Jun Sun");
+MODULE_LICENSE("GPL");
