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[PATCH] ARM: 2701/1: free up ixp2000 timer 4 for the watchdog

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Patch from Lennert Buytenhek

The IXP2000 has four timers, but if we're on an A-step IXP2800, timer
2 and 3 don't work.  We need two timers for timekeeping (one for the
timer interrupt and one for tracking missed jiffies), so on early
IXP2800s we have no other choice but to use timer 1 and 4 for that,
but on all other IXP2000s we'd rather leave timer 4 free since that's
the only timer we can use for the watchdog.
So, on buggy IXP2000s (i.e. the A-step IXP2800) we use timer 4 for
tracking missed jiffies, and on all all non-buggy IXP2000s (i.e.
everything but the A-step IXP2800) we use timer 2.
On a pre-production IXP2800, this patch should print these messages
on boot:
	Enabling IXP2800 erratum #25 workaround
	Unable to use IXP2000 watchdog due to IXP2800 erratum #25
On any non-buggy IXP2800 (as well as on IXP2400s) you shouldn't see
anything at all, and the watchdog should be usable again.

Signed-off-by: Lennert Buytenhek
Signed-off-by: Deepak Saxena
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Lennert Buytenhek 2005-06-20 18:51:07 +01:00 committed by Russell King
parent c0da085ad2
commit e4fe19819e
3 changed files with 33 additions and 9 deletions
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34
arch/arm/mach-ixp2000/core.c
View file

@ -162,12 +162,13 @@ void __init ixp2000_map_io(void)
static unsigned ticks_per_jiffy;
static unsigned ticks_per_usec;
static unsigned next_jiffy_time;
static volatile unsigned long *missing_jiffy_timer_csr;
unsigned long ixp2000_gettimeoffset (void)
{
unsigned long offset;
offset = next_jiffy_time - *IXP2000_T4_CSR;
offset = next_jiffy_time - *missing_jiffy_timer_csr;
return offset / ticks_per_usec;
}
@ -179,7 +180,7 @@ static int ixp2000_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
/* clear timer 1 */
ixp2000_reg_write(IXP2000_T1_CLR, 1);
while ((next_jiffy_time - *IXP2000_T4_CSR) > ticks_per_jiffy) {
while ((next_jiffy_time - *missing_jiffy_timer_csr) > ticks_per_jiffy) {
timer_tick(regs);
next_jiffy_time -= ticks_per_jiffy;
}
@ -197,20 +198,37 @@ static struct irqaction ixp2000_timer_irq = {
void __init ixp2000_init_time(unsigned long tick_rate)
{
ixp2000_reg_write(IXP2000_T1_CLR, 0);
ixp2000_reg_write(IXP2000_T4_CLR, 0);
ticks_per_jiffy = (tick_rate + HZ/2) / HZ;
ticks_per_usec = tick_rate / 1000000;
/*
* We use timer 1 as our timer interrupt.
*/
ixp2000_reg_write(IXP2000_T1_CLR, 0);
ixp2000_reg_write(IXP2000_T1_CLD, ticks_per_jiffy - 1);
ixp2000_reg_write(IXP2000_T1_CTL, (1 << 7));
/*
* We use T4 as a monotonic counter to track missed jiffies
* We use a second timer as a monotonic counter for tracking
* missed jiffies. The IXP2000 has four timers, but if we're
* on an A-step IXP2800, timer 2 and 3 don't work, so on those
* chips we use timer 4. Timer 4 is the only timer that can
* be used for the watchdog, so we use timer 2 if we're on a
* non-buggy chip.
*/
ixp2000_reg_write(IXP2000_T4_CLD, -1);
ixp2000_reg_write(IXP2000_T4_CTL, (1 << 7));
if ((*IXP2000_PRODUCT_ID & 0x001ffef0) == 0x00000000) {
printk(KERN_INFO "Enabling IXP2800 erratum #25 workaround\n");
ixp2000_reg_write(IXP2000_T4_CLR, 0);
ixp2000_reg_write(IXP2000_T4_CLD, -1);
ixp2000_reg_write(IXP2000_T4_CTL, (1 << 7));
missing_jiffy_timer_csr = IXP2000_T4_CSR;
} else {
ixp2000_reg_write(IXP2000_T2_CLR, 0);
ixp2000_reg_write(IXP2000_T2_CLD, -1);
ixp2000_reg_write(IXP2000_T2_CTL, (1 << 7));
missing_jiffy_timer_csr = IXP2000_T2_CSR;
}
next_jiffy_time = 0xffffffff;
/* register for interrupt */

7
drivers/char/watchdog/ixp2000_wdt.c
View file

@ -192,7 +192,12 @@ static struct miscdevice ixp2000_wdt_miscdev =
static int __init ixp2000_wdt_init(void)
{
wdt_tick_rate = (*IXP2000_T1_CLD * HZ)/ 256;;
if ((*IXP2000_PRODUCT_ID & 0x001ffef0) == 0x00000000) {
printk(KERN_INFO "Unable to use IXP2000 watchdog due to IXP2800 erratum #25.\n");
return -EIO;
}
wdt_tick_rate = (*IXP2000_T1_CLD * HZ) / 256;
return misc_register(&ixp2000_wdt_miscdev);
}

1
include/asm-arm/arch-ixp2000/ixp2000-regs.h
View file

@ -363,6 +363,7 @@
#define IXP2000_MIN_REV_MASK 0x0000000F
#define IXP2000_PROD_ID_MASK 0xFFFFFFFF
#define IXP2000_PRODUCT_ID GLOBAL_REG(0x00)
#define IXP2000_MISC_CONTROL GLOBAL_REG(0x04)
#define IXP2000_MSF_CLK_CNTRL GLOBAL_REG(0x08)
#define IXP2000_RESET0 GLOBAL_REG(0x0c)