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author | Lennert Buytenhek <buytenh@org.rmk.(none)> | 2005-06-20 18:51:07 +0100 |
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committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2005-06-20 18:51:07 +0100 |
commit | e4fe19819ef32950541503042f32e71b67edffc7 (patch) | |
tree | 57c68008ba8c3b3a9f6ab8950c620175e9405569 /arch/arm/mach-ixp2000/core.c | |
parent | c0da085ad2e6b1419b8a7439538f7f15eb5c4777 (diff) | |
download | kernel_samsung_tuna-e4fe19819ef32950541503042f32e71b67edffc7.zip kernel_samsung_tuna-e4fe19819ef32950541503042f32e71b67edffc7.tar.gz kernel_samsung_tuna-e4fe19819ef32950541503042f32e71b67edffc7.tar.bz2 |
[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: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/mach-ixp2000/core.c')
-rw-r--r-- | arch/arm/mach-ixp2000/core.c | 34 |
1 files changed, 26 insertions, 8 deletions
diff --git a/arch/arm/mach-ixp2000/core.c b/arch/arm/mach-ixp2000/core.c index 4f3c3d5..fc05555 100644 --- a/arch/arm/mach-ixp2000/core.c +++ b/arch/arm/mach-ixp2000/core.c @@ -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 */ |