Commit e4fe1981 authored by Lennert Buytenhek's avatar Lennert Buytenhek Committed by Russell King
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[PATCH] ARM: 2701/1: free up ixp2000 timer 4 for the watchdog 



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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent c0da085a

arch/arm/mach-ixp2000/core.c

+26 −8
Original line number Diff line number Diff line
@@ -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.

	 */

	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 */

drivers/char/watchdog/ixp2000_wdt.c

+6 −1
Original line number Diff line number Diff line
@@ -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);

}

include/asm-arm/arch-ixp2000/ixp2000-regs.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

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