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authorLennert Buytenhek <buytenh@org.rmk.(none)>2005-06-20 18:51:07 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2005-06-20 18:51:07 +0100
commite4fe19819ef32950541503042f32e71b67edffc7 (patch)
tree57c68008ba8c3b3a9f6ab8950c620175e9405569
parentc0da085ad2e6b1419b8a7439538f7f15eb5c4777 (diff)
[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>
-rw-r--r--arch/arm/mach-ixp2000/core.c34
-rw-r--r--drivers/char/watchdog/ixp2000_wdt.c7
-rw-r--r--include/asm-arm/arch-ixp2000/ixp2000-regs.h1
3 files changed, 33 insertions, 9 deletions
diff --git a/arch/arm/mach-ixp2000/core.c b/arch/arm/mach-ixp2000/core.c
index 4f3c3d5c781..fc0555596d6 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 */
diff --git a/drivers/char/watchdog/ixp2000_wdt.c b/drivers/char/watchdog/ixp2000_wdt.c
index ab659d37b4d..4e98c215e5b 100644
--- a/drivers/char/watchdog/ixp2000_wdt.c
+++ b/drivers/char/watchdog/ixp2000_wdt.c
@@ -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);
}
diff --git a/include/asm-arm/arch-ixp2000/ixp2000-regs.h b/include/asm-arm/arch-ixp2000/ixp2000-regs.h
index 6c56708d0ff..a1d9e181b10 100644
--- a/include/asm-arm/arch-ixp2000/ixp2000-regs.h
+++ b/include/asm-arm/arch-ixp2000/ixp2000-regs.h
@@ -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)