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6bb74df481
This patch resolves the issue found here: http://bugme.osdl.org/show_bug.cgi?id=7426 The basic summary is: Currently we register most of i386/x86_64 clocksources at module_init time. Then we enable clocksource selection at late_initcall time. This causes some problems for drivers that use gettimeofday for init calibration routines (specifically the es1968 driver in this case), where durring module_init, the only clocksource available is the low-res jiffies clocksource. This may cause slight calibration errors, due to the small sampling time used. It should be noted that drivers that require fine grained time may not function on architectures that do not have better then jiffies resolution timekeeping (there are a few). However, this does not discount the reasonable need for such fine-grained timekeeping at init time. Thus the solution here is to register clocksources earlier (ideally when the hardware is being initialized), and then we enable clocksource selection at fs_initcall (before device_initcall). This patch should probably get some testing time in -mm, since clocksource selection is one of the most important issues for correct timekeeping, and I've only been able to test this on a few of my own boxes. Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
120 lines
3.0 KiB
C
120 lines
3.0 KiB
C
#include <linux/clocksource.h>
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#include <linux/string.h>
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#include <linux/errno.h>
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#include <linux/timex.h>
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#include <linux/init.h>
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#include <asm/pgtable.h>
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#include <asm/io.h>
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#include "mach_timer.h"
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#define CYCLONE_CBAR_ADDR 0xFEB00CD0 /* base address ptr */
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#define CYCLONE_PMCC_OFFSET 0x51A0 /* offset to control register */
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#define CYCLONE_MPCS_OFFSET 0x51A8 /* offset to select register */
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#define CYCLONE_MPMC_OFFSET 0x51D0 /* offset to count register */
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#define CYCLONE_TIMER_FREQ 99780000 /* 100Mhz, but not really */
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#define CYCLONE_TIMER_MASK CLOCKSOURCE_MASK(32) /* 32 bit mask */
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int use_cyclone = 0;
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static void __iomem *cyclone_ptr;
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static cycle_t read_cyclone(void)
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{
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return (cycle_t)readl(cyclone_ptr);
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}
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static struct clocksource clocksource_cyclone = {
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.name = "cyclone",
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.rating = 250,
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.read = read_cyclone,
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.mask = CYCLONE_TIMER_MASK,
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.mult = 10,
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.shift = 0,
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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};
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static int __init init_cyclone_clocksource(void)
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{
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unsigned long base; /* saved value from CBAR */
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unsigned long offset;
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u32 __iomem* volatile cyclone_timer; /* Cyclone MPMC0 register */
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u32 __iomem* reg;
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int i;
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/* make sure we're on a summit box: */
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if (!use_cyclone)
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return -ENODEV;
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printk(KERN_INFO "Summit chipset: Starting Cyclone Counter.\n");
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/* find base address: */
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offset = CYCLONE_CBAR_ADDR;
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reg = ioremap_nocache(offset, sizeof(reg));
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if (!reg) {
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printk(KERN_ERR "Summit chipset: Could not find valid CBAR register.\n");
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return -ENODEV;
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}
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/* even on 64bit systems, this is only 32bits: */
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base = readl(reg);
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if (!base) {
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printk(KERN_ERR "Summit chipset: Could not find valid CBAR value.\n");
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return -ENODEV;
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}
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iounmap(reg);
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/* setup PMCC: */
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offset = base + CYCLONE_PMCC_OFFSET;
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reg = ioremap_nocache(offset, sizeof(reg));
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if (!reg) {
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printk(KERN_ERR "Summit chipset: Could not find valid PMCC register.\n");
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return -ENODEV;
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}
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writel(0x00000001,reg);
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iounmap(reg);
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/* setup MPCS: */
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offset = base + CYCLONE_MPCS_OFFSET;
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reg = ioremap_nocache(offset, sizeof(reg));
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if (!reg) {
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printk(KERN_ERR "Summit chipset: Could not find valid MPCS register.\n");
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return -ENODEV;
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}
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writel(0x00000001,reg);
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iounmap(reg);
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/* map in cyclone_timer: */
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offset = base + CYCLONE_MPMC_OFFSET;
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cyclone_timer = ioremap_nocache(offset, sizeof(u64));
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if (!cyclone_timer) {
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printk(KERN_ERR "Summit chipset: Could not find valid MPMC register.\n");
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return -ENODEV;
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}
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/* quick test to make sure its ticking: */
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for (i = 0; i < 3; i++){
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u32 old = readl(cyclone_timer);
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int stall = 100;
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while (stall--)
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barrier();
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if (readl(cyclone_timer) == old) {
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printk(KERN_ERR "Summit chipset: Counter not counting! DISABLED\n");
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iounmap(cyclone_timer);
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cyclone_timer = NULL;
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return -ENODEV;
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}
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}
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cyclone_ptr = cyclone_timer;
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/* sort out mult/shift values: */
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clocksource_cyclone.shift = 22;
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clocksource_cyclone.mult = clocksource_hz2mult(CYCLONE_TIMER_FREQ,
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clocksource_cyclone.shift);
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return clocksource_register(&clocksource_cyclone);
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}
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arch_initcall(init_cyclone_clocksource);
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