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Subject[PATCH] CMOS locking for 2.4 (was: /proc/apm slows system time)
Alan Cox wrote:
>
> > Is there at least away we can recover the proper system time
> > after these stalls?
> >
> > re-read the RTC -- but that's pretty slow and ugly
>
> Be very careful doing that in 2.4test. The 2.2 CMOS locking patches are not yet
> in so there is already a window for CMOS problems as far as I can tell. Don't
> make it bigger

This should cover CMOS locking for 2400-prerel.

Paul.

diff -ur linux-orig/Documentation/rtc.txt linux/Documentation/rtc.txt
--- linux-orig/Documentation/rtc.txt Fri May 26 16:03:14 2000
+++ linux/Documentation/rtc.txt Tue Jan 2 05:48:03 2001
@@ -56,7 +56,7 @@
exclusive access to the device for your applications.

The alarm and/or interrupt frequency are programmed into the RTC via
-various ioctl(2) calls as listed in ./include/linux/mc146818rtc.h
+various ioctl(2) calls as listed in ./include/linux/rtc.h
Rather than write 50 pages describing the ioctl() and so on, it is
perhaps more useful to include a small test program that demonstrates
how to use them, and demonstrates the features of the driver. This is
@@ -81,7 +81,7 @@
*/

#include <stdio.h>
-#include <linux/mc146818rtc.h>
+#include <linux/rtc.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/types.h>
diff -ur linux-orig/arch/i386/kernel/process.c linux/arch/i386/kernel/process.c
--- linux-orig/arch/i386/kernel/process.c Mon Jan 1 04:36:51 2001
+++ linux/arch/i386/kernel/process.c Tue Jan 2 08:58:50 2001
@@ -32,6 +32,7 @@
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/init.h>
+#include <linux/mc146818rtc.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -257,6 +258,8 @@
*/
void machine_real_restart(unsigned char *code, int length)
{
+ unsigned long flags;
+
cli();

/* Write zero to CMOS register number 0x0f, which the BIOS POST
@@ -266,10 +269,12 @@
disable NMIs by setting the top bit in the CMOS address register,
as we're about to do peculiar things to the CPU. I'm not sure if
`outb_p' is needed instead of just `outb'. Use it to be on the
- safe side. */
+ safe side. (Yes, CMOS_WRITE does outb_p's. - Paul G.)
+ */

- outb_p (0x8f, 0x70);
- outb_p (0x00, 0x71);
+ spin_lock_irqsave(&rtc_lock, flags);
+ CMOS_WRITE(0x00, 0x8f);
+ spin_unlock_irqrestore(&rtc_lock, flags);

/* Remap the kernel at virtual address zero, as well as offset zero
from the kernel segment. This assumes the kernel segment starts at
diff -ur linux-orig/drivers/char/nvram.c linux/drivers/char/nvram.c
--- linux-orig/drivers/char/nvram.c Mon Nov 20 04:12:31 2000
+++ linux/drivers/char/nvram.c Tue Jan 2 05:50:36 2001
@@ -107,8 +107,6 @@
#include <asm/uaccess.h>
#include <asm/system.h>

-extern spinlock_t rtc_lock;
-
static int nvram_open_cnt; /* #times opened */
static int nvram_open_mode; /* special open modes */
#define NVRAM_WRITE 1 /* opened for writing (exclusive) */
diff -ur linux-orig/drivers/char/rtc.c linux/drivers/char/rtc.c
--- linux-orig/drivers/char/rtc.c Mon Nov 20 04:19:54 2000
+++ linux/drivers/char/rtc.c Tue Jan 2 05:50:29 2001
@@ -89,8 +89,6 @@

static DECLARE_WAIT_QUEUE_HEAD(rtc_wait);

-extern spinlock_t rtc_lock;
-
static struct timer_list rtc_irq_timer;

static loff_t rtc_llseek(struct file *file, loff_t offset, int origin);
diff -ur linux-orig/drivers/ide/hd.c linux/drivers/ide/hd.c
--- linux-orig/drivers/ide/hd.c Mon Nov 20 04:19:58 2000
+++ linux/drivers/ide/hd.c Tue Jan 2 08:05:44 2001
@@ -738,6 +738,7 @@
if (!NR_HD) {
extern struct drive_info drive_info;
unsigned char *BIOS = (unsigned char *) &drive_info;
+ unsigned long flags;
int cmos_disks;

for (drive=0 ; drive<2 ; drive++) {
@@ -773,10 +774,15 @@
Needless to say, a non-zero value means we have
an AT controller hard disk for that drive.

-
+ Currently the rtc_lock is a bit academic since this
+ driver is non-modular, but someday... ? Paul G.
*/

- if ((cmos_disks = CMOS_READ(0x12)) & 0xf0) {
+ spin_lock_irqsave(&rtc_lock, flags);
+ cmos_disks = CMOS_READ(0x12);
+ spin_unlock_irqrestore(&rtc_lock, flags);
+
+ if (cmos_disks & 0xf0) {
if (cmos_disks & 0x0f)
NR_HD = 2;
else
diff -ur linux-orig/drivers/ide/ide-geometry.c linux/drivers/ide/ide-geometry.c
--- linux-orig/drivers/ide/ide-geometry.c Tue Aug 8 03:56:16 2000
+++ linux/drivers/ide/ide-geometry.c Tue Jan 2 07:25:10 2001
@@ -3,6 +3,7 @@
*/
#include <linux/config.h>
#include <linux/ide.h>
+#include <linux/mc146818rtc.h>
#include <asm/io.h>

/*
@@ -46,13 +47,15 @@
extern struct drive_info_struct drive_info;
byte cmos_disks, *BIOS = (byte *) &drive_info;
int unit;
+ unsigned long flags;

#ifdef CONFIG_BLK_DEV_PDC4030
if (hwif->chipset == ide_pdc4030 && hwif->channel != 0)
return;
#endif /* CONFIG_BLK_DEV_PDC4030 */
- outb_p(0x12,0x70); /* specify CMOS address 0x12 */
- cmos_disks = inb_p(0x71); /* read the data from 0x12 */
+ spin_lock_irqsave(&rtc_lock, flags);
+ cmos_disks = CMOS_READ(0x12);
+ spin_unlock_irqrestore(&rtc_lock, flags);
/* Extract drive geometry from CMOS+BIOS if not already setup */
for (unit = 0; unit < MAX_DRIVES; ++unit) {
ide_drive_t *drive = &hwif->drives[unit];
diff -ur linux-orig/include/asm-i386/floppy.h linux/include/asm-i386/floppy.h
--- linux-orig/include/asm-i386/floppy.h Mon Nov 20 04:17:40 2000
+++ linux/include/asm-i386/floppy.h Tue Jan 2 06:19:09 2001
@@ -285,8 +285,28 @@
static int FDC1 = 0x3f0;
static int FDC2 = -1;

-#define FLOPPY0_TYPE ((CMOS_READ(0x10) >> 4) & 15)
-#define FLOPPY1_TYPE (CMOS_READ(0x10) & 15)
+/*
+ * Floppy types are stored in the rtc's CMOS RAM and so rtc_lock
+ * is needed to prevent corrupted CMOS RAM in case "insmod floppy"
+ * coincides with another rtc CMOS user. Paul G.
+ */
+#define FLOPPY0_TYPE ({ \
+ unsigned long flags; \
+ unsigned char val; \
+ spin_lock_irqsave(&rtc_lock, flags); \
+ val = (CMOS_READ(0x10) >> 4) & 15; \
+ spin_unlock_irqrestore(&rtc_lock, flags); \
+ val; \
+})
+
+#define FLOPPY1_TYPE ({ \
+ unsigned long flags; \
+ unsigned char val; \
+ spin_lock_irqsave(&rtc_lock, flags); \
+ val = CMOS_READ(0x10) & 15; \
+ spin_unlock_irqrestore(&rtc_lock, flags); \
+ val; \
+})

#define N_FDC 2
#define N_DRIVE 8
diff -ur linux-orig/include/linux/mc146818rtc.h linux/include/linux/mc146818rtc.h
--- linux-orig/include/linux/mc146818rtc.h Wed Jun 28 11:39:35 2000
+++ linux/include/linux/mc146818rtc.h Tue Jan 2 05:21:51 2001
@@ -15,6 +15,8 @@
#include <linux/rtc.h> /* get the user-level API */
#include <asm/mc146818rtc.h> /* register access macros */

+extern spinlock_t rtc_lock; /* serialize CMOS RAM access */
+
/**********************************************************************
* register summary
**********************************************************************/
diff -ur linux-orig/include/linux/rtc.h linux/include/linux/rtc.h
--- linux-orig/include/linux/rtc.h Wed Jul 12 04:18:51 2000
+++ linux/include/linux/rtc.h Tue Jan 2 05:37:04 2001
@@ -2,6 +2,8 @@
* Generic RTC interface.
* This version contains the part of the user interface to the Real Time Clock
* service. It is used with both the legacy mc146818 and also EFI
+ * Struct rtc_time and first 12 ioctl by Paul Gortmaker, 1996 - separated out
+ * from <linux/mc146818rtc.h> to this file for 2.4 kernels.
*
* Copyright (C) 1999 Hewlett-Packard Co.
* Copyright (C) 1999 Stephane Eranian <eranian@hpl.hp.com>


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